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11/7/13 Charging Lithium-Ion Batteries – Battery University batteryuniversity.com/learn/article/charging_lithium_ion_batteries 1/50 Charging Lithium-ion Charging and discharging batteries is a chemical reaction, but Li-ion is claimed as an exception. Here, battery scientists talk about energies flowing in and out as part of ion movement between anode and cathode. This claim has merits, but if the scientists were totally right then the battery would live forever, and this is wishful thinking. The experts blame capacity fade on ions getting trapped. For simplicity, we consider aging a corrosion that affects all battery systems. The Liion charger is a voltage-limiting device that is similar to the lead acid system. The difference lies in a higher voltage per cell, tighter voltage tolerance and the absence of trickle or float charge at full charge. While lead acid offers some flexibility in terms of voltage cutoff, manufacturers of Liion cells are very strict on the correct setting because Li-ion cannot accept overcharge. The so-called miracle charger that promises to prolong battery life and methods that pump extra capacity into the cell do not exist here. Li-ion is a “clean” system and only takes what it can absorb. Anything extra causes stress. Most cells charge to 4.20V/cell with a tolerance of +/–50mV/cell. Higher voltages could increase the capacity, but the resulting cell oxidation would reduce service life. More important is the safety concern if charging beyond 4.20V/cell. Figure 1 shows the voltage and current signature as lithium-ion passes through the stages for constant current and topping charge. Figure 1: Charge stages of lithium-ion. Li-ion is fully charged when the current drops to a predetermined level or levels out at the end of Stage 2. In lieu of trickle charge, some chargers apply a topping charge when the voltage drops to 4.05V/cell (Stage 4). Courtesy of Cadex The charge rate of a typical consumer Li-ion battery is between 0.5 and 1C in Stage 1, and the charge time is about three hours. Manufacturers recommend charging the 18650 cell at 0.8C or less. Charge efficiency is 97 to 99 percent and the cell remains cool during charge. Some Li-ion packs may experience a temperature rise of about 5ºC (9ºF) when reaching full charge. This could be due to the protection circuit and/or elevated internal resistance. Full charge occurs when the battery reaches the voltage threshold and the current drops to three percent of the rated current. A battery is also considered fully charged if the current levels off and cannot go down further. Elevated self-discharge might be the cause of this condition. Increasing the charge current does not hasten the full-charge state by much. Although the battery reaches the voltage peak quicker with a fast charge, the saturation charge will take longer accordingly. The amount of charge current applied simply alters the time required for each stage; Stage 1 will be shorter but the saturation Stage 2 will take longer. A high current charge will, however, quickly fill the battery to about 70 percent. Li-ion does not need to be fully charged, as is the case with lead acid, nor is it desirable to do so. In fact, it is better not to fully charge, because high voltages stresses the battery. Choosing a lower voltage threshold, or eliminating the saturation charge altogether, prolongs battery life but this reduces the runtime. Since the consumer market promotes maximum runtime, these chargers go for maximum capacity rather than extended service life.

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Charging Lithium-ion

Charging and discharging batteries is a chemical reaction, but Li-ion is claimed as an exception. Here, battery scientists talk about energies flowing in and out as

part of ion movement between anode and cathode. This claim has merits, but if the scientists were totally right then the battery would live forever, and this is wishful

thinking. The experts blame capacity fade on ions getting trapped. For simplicity, we consider aging a corrosion that affects all battery systems.

The Li‑ion charger is a voltage-limiting device that is similar to the lead acid system. The difference lies in a higher voltage per cell, tighter voltage tolerance and the

absence of trickle or float charge at full charge. While lead acid offers some flexibility in terms of voltage cut‑off, manufacturers of Li‑ion cells are very strict on the

correct setting because Li-ion cannot accept overcharge. The so-called miracle charger that promises to prolong battery life and methods that pump extra capacity

into the cell do not exist here. Li-ion is a “clean” system and only takes what it can absorb. Anything extra causes stress.

Most cells charge to 4.20V/cell with a tolerance of +/–50mV/cell. Higher voltages could increase the capacity, but the resulting cell oxidation would reduce service life.

More important is the safety concern if charging beyond 4.20V/cell. Figure 1 shows the voltage and current signature as lithium-ion passes through the stages for

constant current and topping charge.

Figure 1: Charge stages of lithium-ion. Li-ion is fully charged when the current drops to a predetermined level or levels out at the end of Stage 2. In lieu of trickle

charge, some chargers apply a topping charge when the voltage drops to 4.05V/cell (Stage 4).

Courtesy of Cadex

The charge rate of a typical consumer Li-ion battery is between 0.5 and 1C in Stage 1, and the charge time is about three hours. Manufacturers recommend charging

the 18650 cell at 0.8C or less. Charge efficiency is 97 to 99 percent and the cell remains cool during charge. Some Li-ion packs may experience a temperature rise of

about 5ºC (9ºF) when reaching full charge. This could be due to the protection circuit and/or elevated internal resistance. Full charge occurs when the battery reaches

the voltage threshold and the current drops to three percent of the rated current. A battery is also considered fully charged if the current levels off and cannot go down

further. Elevated self-discharge might be the cause of this condition.

Increasing the charge current does not hasten the full-charge state by much. Although the battery reaches the voltage peak quicker with a fast charge, the saturation

charge will take longer accordingly. The amount of charge current applied simply alters the time required for each stage; Stage 1 will be shorter but the saturation

Stage 2 will take longer. A high current charge will, however, quickly fill the battery to about 70 percent.

Li-ion does not need to be fully charged, as is the case with lead acid, nor is it desirable to do so. In fact, it is better not to fully charge, because high voltages

stresses the battery. Choosing a lower voltage threshold, or eliminating the saturation charge altogether, prolongs battery life but this reduces the runtime. Since the

consumer market promotes maximum runtime, these chargers go for maximum capacity rather than extended service life.

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Some lower-cost consumer chargers may use the simplified “charge-and-run” method that charges a lithium-ion battery in one hour or less without going to the

Stage 2 saturation charge. “Ready” appears when the battery reaches the voltage threshold at Stage 1. Since the state-of-charge (SoC) at this point is only about 85

percent, the user may complain of short runtime, not knowing that the charger is to blame. Many warranty batteries are being replaced for this reason, and this

phenomenon is especially common in the cellular industry.

Avoiding full charge has benefits, and some manufacturers set the charge threshold lower on purpose to prolong battery life. Table 2 illustrates the estimated

capacities when charged to different voltage thresholds with and without saturation charge.

Charge V/cellCapacity at

cut-off voltageCharge time

Capacity with full

saturation

3.80

3.90

4.00

4.10

4.20

60%

70%

75%

80%

85%

120 min

135 min

150 min

165 min

180 min

65%

76%

82%

87%

100%

Table 2: Typical charge characteristics of lithium-ion. Adding full saturation at the set voltage boosts the capacity by about 10 percent but adds stress due to high

voltage.

When the battery is first put on charge, the voltage shoots up quickly. This behavior can be compared to lifting a heavy weight with an elastic band. The lifting arm

moves up quickly but the weight lags behind. The voltage of the charging battery will only catch up when the battery is almost fully charged (see Figure 3. This charge

characteristic is typical of all batteries.

Figure 3: Capacity as a

function of charge

voltage on a lithium-ion

battery

The capacity trails the

charge voltage, like

lifting a heavy weight

with an elastic band.

Courtesy of Cadex

Relying on the closed circuit voltage (CCV) to read the available capacity during charge is impractical. The open circuit voltage (OCT) can, however, be used to predict

state-of-charge after the battery has rested for a few hours. The rest period calms the agitated battery to regain equilibrium. Similar to all batteries, temperature affects

the OCV. Read "How to Measure State-of-Charge".

Li-ion cannot absorb overcharge, and when fully charged the charge current must be cut off. A continuous trickle charge would cause plating of metallic lithium, and

this could compromise safety. To minimize stress, keep the lithium-ion battery at the 4.20V/cell peak voltage as short a time as possible.

Once the charge is terminated, the battery voltage begins to drop, and this eases the voltage stress. Over time, the open-circuit voltage will settle to between 3.60 and

3.90V/cell. Note that a Li-ion battery that received a fully saturated charge will keep the higher voltage longer than one that was fast-charged and terminated at the

voltage threshold without a saturation charge.

If a lithium-ion battery must be left in the charger for operational readiness, some chargers apply a brief topping charge to compensate for the small self-discharge

the battery and its protective circuit consume. The charger may kick in when the open-circuit voltage drops to 4.05V/cell and turn off again at a high 4.20V/cell.

Chargers made for operational readiness, or standby mode, often let the battery voltage drop to 4.00V/cell and recharge to only 4.05V/cell instead of the full 4.20V/cell.

This reduces voltage-related stress and prolongs battery life.

Some portable devices sit in a charge cradle in the on position. The current drawn through the device is called the parasitic load and can distort the charge cycle.

Battery manufacturers advise against parasitic load because it induces mini-cycles. The battery is continuously being discharged to 4.20V/cell and then charged by

the device. The stress level on the battery is especially high because the cycles occur at the 4.20V/cell threshold.

A portable device must be turned off during charge. This allows the battery to reach the set threshold voltage unhindered, and enables terminating charge on low

current. A parasitic load confuses the charger by depressing the battery voltage and preventing the current in the saturation stage to drop low. A battery may be fully

charged, but the prevailing conditions prompt a continued charge. This causes undue battery stress and compromises safety.

Battery professionals agree that charging lithium-ion batteries is simpler and more straightforward than nickel-based systems. Besides meeting the voltage

tolerances, the charge circuits are relatively simple. Limiting voltage and observing low current in triggering “ready” is easier than analyzing complex signatures that

may change with age. Charge currents with Li-ion are less critical and can vary widely. Any charge will do, including energy from a renewable resource such as a

solar panel or wind turbine. Charge absorption is very high and with a low and intermittent charge, charging simply takes a little longer without negatively affecting the

battery. The absence of trickle charge further helps simplify the charger.

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Tweet 118 192

Overcharging Lithium-ion

Lithium-ion operates safely within the designated operating voltages; however, the battery becomes unstable if inadvertently charged to a higher than specified

voltage. Prolonged charging above 4.30V forms plating of metallic lithium on the anode, while the cathode material becomes an oxidizing agent, loses stability and

produces carbon dioxide (CO2). The cell pressure rises, and if charging is allowed to continue the current interrupt device (CID) responsible for cell safety

disconnects the current at 1,380kPa (200psi).

Should the pressure rise further, a safety membrane bursts open at 3,450kPa (500psi) and the cell might eventually vent with flame. The thermal runaway moves

lower when the battery is fully charged; for Li-cobalt this threshold is between 130–150C°C (266–302°F), nickel-manganese-cobalt (NMC) is 170–180°C (338–

356°F), and manganese is 250°C (482°F). Li-phosphate enjoys similar and better temperature stabilities than manganese.

Lithium-ion is not the only battery that is a safety hazard if overcharged. Lead- and nickel-based batteries are also known to melt down and cause fire if improperly

handled. Nickel-based batteries have also been recalled for safety concerns. Properly designed charging equipment is paramount for all battery systems.

Over-discharging Lithium-ion

Li-ion should never be discharged too low, and there are several safeguards to prevent this from happening. The equipment cuts off when the battery discharges to

about 3.0V/cell, stopping the current flow. If the discharge continues to about 2.70V/cell or lower, the battery’s protection circuit puts the battery into a sleep mode. This

renders the pack unserviceable and a recharge with most chargers is not possible. To prevent a battery from falling asleep, apply a partial charge before a long

storage period.

Battery manufacturers ship batteries with a 40 percent charge. The low charge state reduces aging-related stress while allowing some self-discharge during

storage. To minimize the current flow for the protection circuit before the battery is sold, advanced Li-ion packs feature a sleep mode that disables the protection

circuit until activated by a brief charge or discharge. Once engaged, the battery remains operational and the on state can no longer be switched back to the standby

mode.

Do not recharge lithium-ion if a cell has stayed at or below 1.5V for more than a week. Copper shunts may have formed inside the cells that can lead to a partial or

total electrical short. If recharged, the cells might become unstable, causing excessive heat or showing other anomalies. Li-ion packs that have been under stress

are more sensitive to mechanical abuse, such as vibration, dropping and exposure to heat.

Charging Lithium-ion Polymer

Charging Li‑ion polymer, also referred as Li-polymer, is very similar to a regular lithium-ion battery and no changes in algorithm are necessary. Most users won’t

even know if their battery is Li‑ion or Li‑polymer. The word “polymer” has been used as promotional hype and does not reflect special attributes other than to know

that the battery is built in a different way to a standard Li-ion.

Most polymer batteries are based on a hybrid architecture that is a cross between Li-ion and Li-polymer. There are many variations within the polymer family, and the

true dry polymer battery for the consumer market is still years away. Also know as the “plastic battery,” this system was first announced in early 2000 but was never

able to attain the conductivity needed for most applications at ambient temperatures. Read more about the Lithium-polymer battery and the Pouch Cell.

Simple Guidelines for Charging Lithium-based Batteries

A portable device should be turned off while charging. This allows the battery to reach the threshold voltage unhindered and reflects the correct saturation

current responsible to terminate the charge. A parasitic load confuses the charger.

Charge at a moderate temperature. Do not charge below freezing.

Lithium-ion does not need to be fully charged; a partial charge is better.

Chargers use different methods for “ready” indication. The light signal may not always indicate a full charge.

Discontinue using charger and/or battery if the battery gets excessively warm.

Before prolonged storage, apply some charge to bring the pack to about half charge.

Over-discharged batteries can be “boosted” to life again. Discard pack if the voltage does not rise to a normal level within a minute while on boost.

104

Comments

On November 10, 2010 at 3:39am

Adley wrote:

Super post there! Comprehensive and w ell collated material. Thanks for sharing.

On November 11, 2010 at 7:41am

Grosser wrote:

Very usefull information here, good thing I fond this page f irst before designing a charger for my custom-made battery pack.

Like 775

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P.S. You’re alw ais talking about a 4,2V like they are the the standardw hat about 3,6V cells?

On November 12, 2010 at 3:52pm

Jason wrote:

Facinating stuff, although I doubt I w ill ever have the ambition to put it use.

On November 21, 2010 at 6:45am

Mike wrote:

Grosser,

3.6 is the nominal delivery voltage of a Li-ion cell, w hile 4.2 is the max charging voltage. They are the same battery. It’s the same situation w ith other battery chemistries, e.g. for a 12V

lead-acid battery, you’d be charging to ~14V

On November 21, 2010 at 7:22pm

Paul Smith wrote:

My Li-ion battery is used in a Canon 50D DSLR camera; The charger blinks to indicate the level of charge. The indications are 1-blink series, 2-blink series, 3-blink series, and steady-on

to indicate full charge. Often I leave the battery in the charger and go to bed if the LED is at the 2-blink state. When I w ake up 4 to 5 hours later, the LED may have been steady-on for 4

hours. I have tw o questions. (1)What harm am I doing to my battery by follow ing this practice and (2)Is the battery fully-charged if I remove it from the charger as soon as the steady-on

state is reached?

On November 22, 2010 at 8:15am

Eduardo wrote:

I need to do the follow ing test:

1 Question;

Have my charge Battery is Full. How time (day) can battery disconnect?

and

2 Questions

What time need battery recharge for has charge Full ?.

PD: My pow er Supply is 3,7 volt

On November 23, 2010 at 6:26pm

MANAS R. PANIGRAHI wrote:

w hat is the w ork of that circuit inside a lithium ion battery?

On November 24, 2010 at 7:29am

Eduardo wrote:

Thak You, unansw er.

The Batery is connected circuit 3,6 volt constant (regulable according to load) and this support a circuit for memory and a processor primary.

Thanks again.

Eduardo

On December 2, 2010 at 1:12am

Steve Webert wrote:

Does it benefit a lithium-ion or lithium-ion-polymer battery to periodically discharge it “fully” (ie, dow n to the above mentioned 2.7V-3.0V range)?

I have read several OEM’s offering differing strategies for optimizing battery life.

Thank you for your time and efforts—I very much appreciate the above instruction.

On December 9, 2010 at 2:02pm

Thomas Vargas wrote:

What about chargin vehicle batteries? This w ill be a big issue if they ever become popular.

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How w ould the graph look if it w ere for vehicles?

On December 17, 2010 at 8:43pm

thomas micciantuono wrote:

Can lithium polymer cell phone batteries be over charged if left on charge to long and if left on to long w ill it diminish battery life.

On December 27, 2010 at 9:27pm

Andy wrote:

I’ve inherited an electric vehicle pow ered by tw o 38V/90Ah lithium-ion batteries. The voltage of both packs read around 9V only! The engine management system reports that a mere 21

hours of operation have been logged thus far. Are these battery packs truly dead-DEAD or is it possible to resuscitate them again in one w ay or another? Please advise. Cheers.

On January 3, 2011 at 10:21pm

Flynn Siy wrote:

I am looking for alternative charges for my HTC Desire. The standard charger that came w ith it is 5V and 1000mah. Since the charger uses a standard micro USB tip, there are a lot of

available chargers out there w ith different Amp rating. Is it advisable to get a low Amp rating such as 500mah, higher amp such as 1200mah or stick w ith the same 1000amp? Is slow

charging better than fast charging?

On January 6, 2011 at 12:50am

Jerry Conrad wrote:

My HTC EVO cellphone shuts dow n w hen the discharge voltage reaches 3.6 volts. Isn’t this reducing the use-capacity of this battery quite a bit?

On January 6, 2011 at 9:59pm

Jovy Macaspac wrote:

I’ve read somew here that a charger w ith a low er voltage rating (e.g., 3.2v) cannot recharge a lithium battery w ith a higher voltage rating (e.g., 3.7v). Is this true? Something to do w ith

electron transfer, I think… If this is true, I’m confused. How can a 3.7v charger charge a 3.2v battery to 4.2v if , w hen they reach the same voltage level (3.7v), it can no longer push said

electrons around the battery?

Another question, if it’s alright: USB chargers have a rating of 5v. Would this cause problems w ith lithium batteries since as stated above, charging above 4.3v causes plating of the

metallic lithium on the anode?

Thanks and more pow er!

Jovy

On January 7, 2011 at 6:47pm

Mr. D wrote:

how can you trickle charge a 12v batt @ 2v trickle and get a full charge . the battery is like a tank, w ith a limitation of it"s rateing ie. 4.2v or 12v ,is the limit that the battery w ill hold,

forceing anything over that w ill start to burn the core of the battery in one w ay or the other ... do i w in a cuppie doll??

On January 9, 2011 at 1:44pm

Vass wrote:

@ Flynn Siy, the ratings of the charger mentioned misguiding me as the standard charger rating should be in terms of volts and Amps/milli amps(mA) but not in mAh. If your concern is

about a charger(i’ll interpret it to 500mA/12mA ) then go for 1200mA. There’s no harm in it. If you go for 500mA, it’ll charge but it become hot due to it’s inability to supply the rating

current(say 1000mA).This inturn drop the voltage. If your concern is about a battery(a standard battery rating w ill be in volts and mAh), go for either one but in reduction in back up, in

case if you chose 500mAh.Hope it cleared your doubt.

Cheers,

Vass.

On January 12, 2011 at 7:03am

Shiwakoti wrote:

How Li-ion battery gets recharged? Why at elevated temperature the battery life gets shortened? Does frequent charging pratice w ithout being fully discharged affect bttery life span? Plz

help..

On January 15, 2011 at 3:55am

Ike wrote:

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“My HTC EVO cellphone shuts dow n w hen the discharge voltage reaches 3.6 volts. Isn’t this reducing the use-capacity of this battery quite a bit?”

—This is to protect the battery: further discharge could destabilize it and next charging could be risky (you may have heard of exploding LiIon batteries…).

Despite more strict cutoff liit, LiIons can store more energy than previous technologies iin same cell size, so you should not consider this a design fault/draw back, just a essential

characteristic feature of this different chemistry.

Shiw akoti, you w ill f ind answ ers to your questions on the articles at this site: esp. in “Is lithium-ion the ideal battery?”. Shortly said, elevated temperature speeds up battery aging (it’s a

chemical reaction a bit like how iron rusts faster in humid climate compared to dry circumstances) and it’s MUCH better to recharge often than let LiIons drain fully.

On January 15, 2011 at 5:43am

Shiwakoti wrote:

Thanks for the answ er..

On January 23, 2011 at 1:08am

STEYAERT.DANIEL wrote:

GOED UITGELEGDE TEKST

On January 23, 2011 at 1:31pm

Curt Eglin wrote:

Excellent material. I now know how to properly charge a 3.7 volt Li-Ion pack I took out of a Blackberry phone that is since defunct. Tnx.

On February 2, 2011 at 2:24pm

Mike wrote:

So in this article is states that Lithium Ion batterys are charged upto 4.2v, w here each cell can handle 4.2v +/- .05v. So the upperbound here is 4.25v to 4.15v. So, if you have a charger

that is push the cells to 4.21v or 4.22v, then it is theoretically f ine.

“A continuous trickle charge above 4.05V/cell w ould causes plating of metallic lithium that could lead to instabilities and compromise safety. “

Here though you say that raising the cell above just over 4v may cause plating. So by specif ication, charging lithium ion cells to 4.2v w ill cause plaiting?

On February 4, 2011 at 6:54am

captainirmak wrote:

i observe (via an application) that my smartphone is reaching till 4191 volts during re-charging the battery by usb cable.

can w e say that battery is died a bit? cos it is not reaching 4.2 or above.

i know that it is very small numbers but curious about it.

and also w hat shold i do max charge the battery?

On February 4, 2011 at 2:21pm

Ken wrote:

The article mentions how dangerous it is to attempt charging cells that have been @<1.5v for just a few days. Well, that has not been in agreement w ith my experience. I occasionally

salvage discarded Li-ion laptop battery packs…disassembling them to harvest the 18650’s for personal r/c and f lashlight use. I commonly pull cells that are totally f lat: 0v, sometimes even

w ith polarity reversed by a few millivolts. In addition, some of the battery packs I ripped into w ere prehistoric by lithium chemistry standards (10 years+). More often than not all cells

w ould recharge to their FULL original rated capacity and perform as new . I alw ays test each cell individually w ith my iMAX B6 charger, manually putting them through at least a couple

500mA to 1Amp discharge/charge cycles. I have *never* experienced any safety nor reliability issues to date.

I w ould also like to brag of having had success restoring substantial capacity to the occasional cells that truly w ere w orn. I w ill never share my method_IT’S MINE !_do not ask.

...Additionally, that procedure IS potentially dangerous and requires mandatory attentive supervision.

I suppose I’ve been laughing all the w ay to the battery bank. I know , horrible joke!

On February 11, 2011 at 1:30pm

TAS wrote:

What i have believed is keeping my laptop plugged in all the time at my desk and using the battery pow er in case of pow er failure or so. We have very frequent pow er cut-dow ns for brief

spans. I also use BatteryCare to notify me of recalibration.

AFAIK Li-ion does not have memory effect and they have PMS circuit built-in so don’t overcharge.

A vendor of notebooks recently opposed and recommended to cycle discharges and recharges regularly to keep the battery healthy and prolong its life.

What’s the bottom line?

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On February 11, 2011 at 1:32pm

tas wrote:

What i have believed is keeping my laptop plugged in all the time at my desk and using the battery pow er in case of pow er failure or so does no harm to my battery pack. We have very

frequent pow er cut-dow ns for brief spans. I also use BatteryCare to notify me of recalibration.

AFAIK Li-ion does not have memory effect and they have PMS circuit built-in so don’t overcharge.

A vendor of notebooks recently opposed and recommended to cycle discharges and recharges regularly to keep the battery healthy and prolong its life.

What’s the bottom line?

On February 15, 2011 at 10:28am

Steven Hess wrote:

I just bought a Bushnell GPS and it has a Li-Ion battery pack. The instructions said to charge the li-Ion batteries for four hours. But upon plugging the charger to the batteries the green light

immediatley came on, indicating a fully charged pack. But the pack is not charged at all. The unit w ill not turn on w ith these batteries. So my question is; Why is the charger displaying a

Green LED w hen in fact the batteries need charged. And is there something I can do to make it start charging because the charger doesn’t charge w hen displaying a green light.

On February 15, 2011 at 1:06pm

Dan wrote:

Mike, I have been thinking of doing some EV experiments using some old laptop cells. They f lat and packaged in plastic bags. What do you think about using this type of cell?

On February 16, 2011 at 12:24pm

Edward wrote:

i got a new phone. and it says b4 i do anything, i need to charge it for a total of 12 hours for it 2 run right, and battery life, blah blah…. but my question is, simple and plain… do i need to

really charge it for the full 12 hours? can i just charge it until it says 100% charged, w hich w ould be in a hour or tw o…. i’ve google’d my question, and i’ve read mixed answ ers… “yes

you should” “no, you don’t have to, because its a lithium-ion” w hoop this, and w hoop that…..

i w ould jus like a simpe answ er.. yes or no… and w hy?

Thanx yous

On February 16, 2011 at 11:49pm

Samer wrote:

hi, i w ould like to know about the f irst charge lithium baattery ?

should i live chargim for 24h ?

thanks

On February 18, 2011 at 2:43am

Betty wrote:

Thanks so much. All the new gadgets (laptops, cell phones, portable TV-DVD kits, etc) don’t specify anything about the Battery “rules’ like they used to in the day of NiCad and NiMH. This

article is very VERY informative and helpful. NOW, i better start unplugging my laptop… thought i w as ‘saving’ the battery by keeping it plugged in w hile using. I guess i probably shouldn’t

be charging my cell phone overnight for 8+hours either?

On February 19, 2011 at 2:33am

Ken wrote:

Great article, very informative. Can anyone help me w ith the follow ing:

I have a Gibson Robot Guitar, the manufacturer states that it runs on:

(2 x 14500) 2.4v 2100mAh lithium rechargeable battery system.

These batteries have been run dow n for some time now and do charge, the manufacturer cannot replace them.

How can the voltage be 2.4v w hen the minimum cell voltage for lithium batteries is 3.6v What should I buy to replace these?

On February 25, 2011 at 9:12pm

marwan saade wrote:

dear sir

i have a vemar jiano helmet w ith integrated bluetooth. by mitake i’ve charged it w ith a nicd charger so the batterie w as distroyed and does not w ork anynore.

w hen i opened the divice i found a li ion battery 3.7v 800ma reference stilo b001011.

please i w ould like to know if there is a w ay to f ix it or recharge it again

if not can i use a a 1cell lypo battery to replace it

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On February 28, 2011 at 11:14pm

to make money forex trading wrote:

You made some respectable points there. I looked on the internet for the issue and located most individuals w ill associate w ith together w ith your w ebsite.

On March 1, 2011 at 9:19am

BJ McGeever wrote:

So should I do my best to keep the battery at 40%? For instance I’ve been letting it hover around 40% by continually plugging and unplugging it. Is that a good idea?

On March 3, 2011 at 6:08pm

EDWARD BRIDGEWATER wrote:

IS IT POSSIBLE TO CHARGE A PACK OF SIX 1.2 LI-ION BATTERIES WITH THE ORIGANAL

CHARGER THAT WAS BUILT FOR CHARGING A PACK OF 6 1.2 BATTERIES

THE BATTERY PACK IS FOR A SCREW/DRIVER DRILL

I WOULD BE VERY GRATFULL FOR ANY HELP

EDWARD.

On March 10, 2011 at 2:31pm

Isidor wrote:

This article has been updated as of March 10, 2011 w ith all new information. Enjoy!

On March 10, 2011 at 8:07pm

Robert wrote:

Nice w ork Isidor. Thank you.

On March 12, 2011 at 10:10am

Lee Kunkiw wrote:

Mar. 13, 2011

To : Robert

I am looking for a 24V bicycle dynamo.

Is it available ? Please help me if you possible.

Thank you.

kunkiw [email protected]

On March 15, 2011 at 11:47am

TAS wrote:

What i have believed is keeping my laptop plugged in all the time at my desk and using the battery pow er in case of pow er failure or so does no harm to my battery pack. We have very

frequent pow er cut-dow ns for brief spans. I also use BatteryCare to notify me of recalibration.

AFAIK Li-ion does not have memory effect and they have PMS circuit built-in so don’t overcharge.

A vendor of notebooks recently opposed and recommended to cycle discharges and recharges regularly to keep the battery healthy and prolong its life.

What’s the bottom line?

On March 17, 2011 at 8:22am

Subbu wrote:

Hi,

I have a simple ARM7 gadget and I w ant to run it on the Li-ion batteries w hich are available cheap. Is there any singly IC chip solution w hich could

a. Charge the battery w hen connected to mains/ USB

b. Indicate the content of charge to ARM7 (ARM7 can query and stop w orking if there is no charge left to function properly)

With best regards,

Subbu.

On March 25, 2011 at 6:44pm

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Francisco Bolivar wrote:

I have an elerctric bike w ith a 600w - 36v motor.

It uses a li-Ion battery.

Usually each time I use the bike its charge drops about 20% of the total battery charge.

WHAT IS BETTER DO DO:

1 - CHARGE THE BATTERY EACH TIME I USE THE BYKE (battery w ith 80% of charge)

2 - CHARGE THE BATTERY ONLY WHEN IT REACHS 60% OR 40% OF CHARGE

On March 27, 2011 at 3:02pm

JimQ wrote:

I w ould like to make a battery pack charger for 4 Li ion cells. Would it be detrimental to limiting the charger voltage to ..say..15 volts. This w ould be w ithin the voltage limit for each cell if

the distribution is even.. How ever, if a cell is shorted there w puld be excessove voltage on the other cells in the series string. Would it be better to design the charger for 4.0 volt peak

and charger the 4 cells in parallel?

On March 28, 2011 at 7:20am

Dominic Gill wrote:

Excellent article. Thanks.

On March 30, 2011 at 1:00pm

MICHEL KUN wrote:

to

kunkiw [email protected]

most dynamo give an AC ourput,

you could try to use a transformer to UP the voltaje

Michel Kun

On March 31, 2011 at 11:47am

Hemanth wrote:

How to remove the charging time li ion battery ? Is there any alternatives w ay ?

On April 10, 2011 at 12:22pm

Wayne Robey wrote:

Informative article but the voltage drop in stage 3 w ould indicate a cell in poor condition. A good cell w ill drop less.

My observation on using batteries after being badly discharged:

About 5 years ago I purchased 40 nearly unused 18X65 cells in 2 cell packs w ith protect circuit. They w are all discharged to cell voltages of .01 to 1.1 v. I charged them for 10 hrs at

c/100 (Now I think c/10 w ould be OK) and 10% failed shorted. The remainder charged w ell at c/10 to 4.2 V. Letting them set 24 hrs, I looked at the voltage drop and classif ied the low est

10% as w eak. Then making a 12 V pack from the remainder I had 2 unused cells classif ied as good. I have had no failures though they have not been treated roughly. I checked the

voltage on the unused cells today. Those marked w eak are above 3.7V and those marked good are above 3.9V.

On April 11, 2011 at 4:33am

michael dalton wrote:

Hey guys,

Just w ant to get this clear in my head. When charging the battery up, I get a controller to put constant current into the battery, then w hen I sense 4.2v/cell, I get the controller to go into

constant voltage (of 4.2) mode and the current w ill die aw ay naturally till fully saturated?

Cheers

MD

On April 11, 2011 at 7:42pm

Wayne Robey wrote:

Michael, NO, the manufacturer recommends that w hen 4.2 v is reached, let the current fall to c/10 then turn it OFF. I think a constant voltage charge can be done but it takes a long time

and must be done at a low er voltage. When the above charging is done and the battery sits 12 hours, measuring the voltage and setting the f loat voltage to that is safe and gives maximum

capacity but that voltage goes dow n as the battery ages. A f loat voltage of 4.1 is reasonable to get best capacity but as the battery gets old, that MIGHT make it age faster. Using the 2

step process of charging at 4.2 v till the current reaches your chosen value (>= c/10) then dropping the voltage to a f loat value w ould be the w ay to quickly charge then f loat it.

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On April 12, 2011 at 4:54am

michael dalton wrote:

Hey Wayne,

Thanks for the reply. So is the current w e are measuring the battery current or the current from the charger.

MD

On April 12, 2011 at 5:13am

michael dalton wrote:

Hey sorry Wayne I think I’m becoming confused. Do you apply a constant voltage in stage 2 until the current reaches c/10 OR manually bring the current dow n to c/10 w ith a controller?

Cheers

MD

On April 12, 2011 at 5:55pm

Erik wrote:

Why can the the battery pack in a Tesla automobile be charged considerably faster w hen the charging unit is 240v vs. 110-120v?

I iam a complete novice, and am w ondering if higher voltage input decreases charging time.

Thanks for any insight you can offer.

On April 13, 2011 at 5:55pm

Wayne Robey wrote:

Michael,

Not all Li cells are the same so the numbers I use below are for the most common ones, some can be charged much faster.

The algorithm is to check the voltage and if it is < ~3 charge at no more than c/10. If it is >3v charge w ith limits of c/2 and 4.2 volts until a current of c/10 is reached, then stop . As

mentioned in the article a voltage < 4.2 increases battery cycle life, shelf life, and reduces discharge capacity for the current cycle. A charge rate < the maximum rated is easyer on the

battery. I think charging w ith variable current is satisfactory if current is limited as specif ied on the data sheet and the voltage is limited to 4.1 volts. This is good for f loat charging and

charging from a variable source.

Erick

There is no inherent reason. It w as designed that w ay to account for commonly available pow er connections, commonly limited to 20A (use at < 80% of limit) at 120v but commonly

available at 50 A or more at 240V.

On April 14, 2011 at 12:47am

Jayk wrote:

I am unable to decide w hich is better - to select a Li-ion battery pack w ith multiple cells or single cell. For example, how to choose betw een a 3.7V, 1500mAhr and a 7.4V, 1500mAhr ?

On April 18, 2011 at 9:41am

MICHEL KUN wrote:

i am

CONFUSED

got some PSP battery from HK

I measuered 4.8 volts on end of charge

4.5 volts after 3 days standing

THEN WHY IS 4.2VOLTS MAXIMUM in all litterature

is this value ABSOLETE???

the battery seem to w ork OK.

thanks in advance for any help or informations

On April 21, 2011 at 4:37am

Alex wrote:

Amazing w ebsite… w ell w ritten .. very very useful

Great Job

On April 24, 2011 at 8:33pm

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nash wrote:

Great article!!

On April 25, 2011 at 6:54am

zz wrote:

w hat happens if you let a li-ion battery connected indefinitely at 4.0V?

On May 3, 2011 at 2:36pm

Ryan wrote:

So I am building a solar pow ered usb charger for an android device. I know that my available curent and voltage at the time of charging w ill vary depending on the panel so in addition to

overcharging I am w ondering if capacitors to buffer pow er is necessary. I have also considered a 3000mAh battery w ith an integrated charging circuit w ould be better. That w ould offer

me more consistent ouput to the device and be a contingency for a lack of or poor lighting. Any ideas w ould help. Kudos on the page, very informative.

On May 5, 2011 at 8:02am

Bilal nasir zargar wrote:

i brought a new battery sony lithium-ion NP-BG1, WHEN I BUY IT , IT WAS IN SLEEPING MOOD, i plugged the charger for charging, but it did not charge, so please suggest me w hat should

i do…

On May 7, 2011 at 9:19pm

mike wrote:

Great article. Well w ritten and very informative - just w hat i w as looking for. Thanks and keep up the excellent w ork.

On May 8, 2011 at 8:35am

JimQ wrote:

Great informative article. For a “12volt” pack, I w ould charge 3 or for Li Ion cells w ith a constant current source and limit the volts per cell by connecting a 4.0 volt zener diode across

each cell. This w ould allow parallel charging but also protect the cells from ‘over voltage’. Does this make sense? The total charging current w ould be limited by the charging source

circuitry and shut off after all cells reached 4.0 volts.

On May 9, 2011 at 1:08pm

TONY wrote:

Li-Ion (Poli)bat

Min V=2.7V ? 3.0V

Midle=3.6-3.7 (Li-Ion Li-Pol)

end of Charging 4.2V Sel Kill 4.3V+

Kill it Fast 4.35 +

On May 9, 2011 at 1:41pm

MICHEL KUN wrote:

w hat about voltajes for

LiFePo4

thanks

On May 9, 2011 at 1:51pm

TONY wrote:

Higher charge voltages boost capacity but low er cycle life and compromise safety.

Li-ion battery to 4.20V/cell. This allow s maximum runtime

We have limited information by how much low er charge voltages prolong battery life; this depends on many conditions, as w e have learned. What w e do know , how ever, is the

capacities. At a charge to 4.10V/cell, the battery holds a capacity that is about 10 percent less than going all the w ay to 4.20V/cell. In terms of optimal longevity, a charge voltage limit of

3.92V/cell w orks best but the capacity w ould be low . Besides selecting the best-suited voltage thresholds, it is also important that the battery does not stay in the high-voltage stage for a

long time and is allow ed to drop after full charge has been reached.

V4.20 end of Charging 100 MA (Panasonic ?)

On May 9, 2011 at 2:04pm

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TONY wrote:

4.20 400+ capacity 80%

4.25 400 bat capacity 25%

4.3v 250 Cycles 50%

4.35v 190 Cycles 25%

On May 12, 2011 at 4:07pm

Skip wrote:

My laptop has a battery rated at 10.8V, 85Wh, 8800mAh. The charger outputs 18.5V, 3.5A, and 65W. I have an old charger that is rated 19V, 3.4A and 65W. Would it be safe to use the

old one?

On May 13, 2011 at 1:38am

Andrea wrote:

Hi,

i w ant to charge a 7.5 v 400 mAh li-ion battery from a small solar panel (6V - 1W).

I w ould connect the solar panel and the battery w ith a voltage regulator or w ith a MPP circuit that f ixed the output voltage adjusting the output current of the solar panel catching alw ays

the maximum pow er from it. In this w ay it’s diff icult charge the battery using the constant current/constant voltage method because i can’t control the charge current and i haven’t enough

pow er from the solar panel.

In conclusion the charging of the battery is done w ith a small and variable charge current. Is that a problem? Can i charge the battery alw ays in slow charge fase and w ith a variable

current? If yes, w hich are the draw backs?

Thank you. regards!

Andrea

On May 26, 2011 at 4:22am

Roy wrote:

Excellent!!! Love the detail…!

On May 26, 2011 at 6:54pm

edy wrote:

w hy lithium can perform fast charging betw een range 20% to 80% SOC only?

Why after 80% SOC charging became slow ?

On June 12, 2011 at 4:27am

Joseph wrote:

My son and I have the same cell phone. His battery charge lasts 1 days and mine only one day. I came here to f ind out w hy. We thought it w as because I w as charging too frequently. I

now believe its because I alw ays left the phone on w hile charging w hereas he turns his off. Thanks for the info!

On June 12, 2011 at 4:29am

Joseph wrote:

oops! 5 days vs 1 day…

On June 14, 2011 at 11:53pm

Nolan wrote:

Great article, thanks for the w riteup.

One question: Would charging a Lithium battery w ith a higher amperage charger (but same voltage) cause any damage to the battery? I’m looking at +300mA to +500mA increase.

On June 15, 2011 at 9:53pm

Craig wrote:

Hello,

I have a cell phone w ith a lithium battery. Is it true that it is better to let the battery almost completely die before charging? I w as told the battery has a memory. Someone also told me that

w as only true w ith NiCd.

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On June 20, 2011 at 8:03am

Terry Bleasdale wrote:

nteresting article but it seems to be contradicted by information here:

http://w w w .electricbikehub.co.nz/?p=919

w hich states that Lithium Polymer can be left on charge betw een bike rides w ithout detriment.

Which is correct please?

On July 4, 2011 at 6:34am

determan wrote:

Hello, my protected 18650 cell faced a high current draw and the protection circuit w ent to sleep mode.. the cell now measures just 0V!.. Do anyone know how can I w ake up such a

cell?.. Your help w ill highly be appreciated.. thanks..

On July 26, 2011 at 4:31am

Javier wrote:

Hey, very good article.

1. Where it says “The battery is continuously being discharged to 4.20V/cell and then charged by the device” I think you mean “The battery is continuously being CHARGED to 4.20V/cell

and then DISCHARGED by the device”

2.¿Its ok to charge to a safe level, say 80% (thus preventing minicycles and overcharging the battery) w ith the device on?

3.¿How can you tell if the charger and/or the device has taken measures to prevent minicycles,overcharges,etc..?

On July 26, 2011 at 2:30pm

Ümit wrote:

Very vey thaks. Usefull informations.

On July 28, 2011 at 3:38am

Amkul wrote:

Hi everyone

I just w anna ask some of the experts here, w hether it’s is OK for me to charge a lithium-ion battery (let’s say a 2Ah), w ith a constant current of 50mA and a f loat voltage of 4.1V?

Despite the slow charging rate (longer time of course), w ould this w ork and w ould there be any other problems?

On August 10, 2011 at 6:50am

JC22 wrote:

So, let me just make sure i have this straight.

I am building a charger and here is my w hat i am doing:

1. When battery is f irst connected charge at c/5 (as recommended by battery manu)

2. While in this stage continually read the voltage i am charging at to produce this current. (Question here: is this correct? or do i need to shut off my charge voltage and w ait about a

second for voltage to settle to battery voltage then read?)

3. When the voltage i am CHARGING at hits 4.2 at this current i charge at a constant 4.2 volts from this point on until the current drops below c/100 (as recommended by battery manu), or

the total charge time exceeds 10hrs (as recommended by manu).

4. When my current hits this low i simply cut out the charge. Question - should i f loat the charge line at some value after charge?

So, basically i just w ant to make sure my method is basically correct. Am i reading the correct voltage to determine w hen to stop fast charging and w hen i am fully charged should i just

leave the charge line at high impedence or should i f loat it to some value?

On August 12, 2011 at 2:28pm

jin wrote:

again, huge amount of misleading info here doesn’t mean everything is w rong. The author actually read these comments, but doesn’t reply to them, as he has deleted my previous post

regarding the reliability of the info presented in this page.

On August 12, 2011 at 2:36pm

jin wrote:

To JC22:

2, you don’t need to cut off your charging voltage to see the stage of your battery.

3, no true; you are risking over-charging the battery at c/100 and more than 10 hours.

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4, you shouldn’t f loat charge a lithium battery

5, When you are fully charged w hich shouldn’t be, you are not a battery. you should just stop risking over-charging yourself.

On August 12, 2011 at 2:40pm

jin wrote:

To Amkul:

You can charge w ith low current, but you shouldn’t f loat charge it. f loat charge means keep charging w ithout stop; you have cut the charging current w hen this current is low er than

50ma; or you risk over-charge your battery.

On August 12, 2011 at 2:44pm

jin wrote:

to Javier:

1, yes, you are right.

2, It is totally f ine.

3, there is no w ay you can tell; other than taking apart the charger and reconstruct the circuitry yourself.

On August 12, 2011 at 2:46pm

jin wrote:

To determan:

If your battery doesn’t charge up in the charger, the circuit probably is damaged.

On August 12, 2011 at 2:49pm

jin wrote:

To Craig:

You can charge lithium any time; memory effect is for the very old nicd only.

On August 12, 2011 at 2:52pm

jin wrote:

To Nolan:

You can, but never charge w ith more than 1C; and that is if you have a 1800mah battery; you shouldn’t charge it w ith 1.8A (1800ma);

On August 12, 2011 at 2:53pm

jin wrote:

Joseph:

It is not true; If you use your cell more than your son; then obviously it w ill last shorter.

On August 12, 2011 at 2:58pm

jin wrote:

I am afraid that you can’t charge a 7.5V battery w ith only 6v solar panel. You need 8.35V, so you need a dc to dc booster w ith regulation,but charging the battery w ith variable current is

f ine.

On August 12, 2011 at 3:04pm

jin wrote:

To skip:

It depends on the charger; but if the output voltage of those 2 charges is more than 12.3 Volt, both are not safe to charge your 10.8v battery.

On August 12, 2011 at 3:07pm

jin wrote:

To Ryan:

Your battery is your buffer. no cap is needed.

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On August 12, 2011 at 3:09pm

jin wrote:

To zz:

You w ill over-charge the battery. It w ill expose eventually.

zz w rote:

w hat happens if you let a li-ion battery connected indefinitely at 4.0V?

On August 12, 2011 at 3:18pm

jin wrote:

TO MICHEL KUN:

As I know , PSP uses 5 volts pow er source. This either means that there is an internal circuit in the battery that boost the voltage from 4.2 to 5+ volts; or the battery is not made out of

lithium. Either case, your battery should be safe to use.

On August 12, 2011 at 3:21pm

jin wrote:

To Jayk:

Depends on your needed voltage and pow er; higher voltage means higher voltage and higher pow er stored.

Jayk w rote:

I am unable to decide w hich is better - to select a Li-ion battery pack w ith multiple cells or single cell. For example, how to choose betw een a 3.7V, 1500mAhr and a 7.4V, 1500mAhr ?

On August 26, 2011 at 4:19am

Garry D wrote:

An enterpreneor claiming, new technology can charge Lithium Ion Battery can charge eight times more life ????

Comments Please ???

On August 26, 2011 at 2:23pm

zz wrote:

you mean explode… interesting, I f igured current must be 0 once voltages equalise, so no overcharge

On August 28, 2011 at 3:39am

jin wrote:

To zz:

w e are not in a perfect w orld. The charging voltage maybe more than 4.20, w hich means there is current going into the battery, and explode it eventually. On the other hand, due to the

age of the cell itself, it may not has its maximun capacity voltage of 4.2. Normally w hen you charge the cell to 4.2 volt, it w ill drop a little bit. If a 4.2 volt charging current is kept charging

that battery, eventually heats and pressure w ill built up and explode the battery.

On August 28, 2011 at 3:42am

jin wrote:

To Garry D,

Yes. technically, it is possible.

On September 8, 2011 at 6:23pm

ray wrote:

if i have a 3.7volts li-ion battery w hat is the output specif ication of my battery charger?

On September 10, 2011 at 4:52am

Garry D wrote:

Which new company has come up w ith this 8 times more life For Lithium Ion Rechargable Battery.

On September 13, 2011 at 11:21am

zz wrote:

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you misunderstood the question

On September 15, 2011 at 5:10pm

Sherri wrote:

I’m really not clear…..

I have a Dell laptop w hich I only use at home. Should I leave it plugged in? should I only plug it in w hen it needs to be charged? I have noticed that it has been getting very hot and at times

the charger seems hot. We have been leaving it plugged in most days, then unplug it at night.

Thank you for clarifying for me!

On September 15, 2011 at 5:25pm

zz wrote:

Most likely 4.2V, but it is also limited in current.

jin, the charging voltage is 4V, no more

On September 16, 2011 at 9:45pm

jin wrote:

TO ray:

Output of your charger should be 4.2V at 200mA-1000mA

On September 16, 2011 at 9:47pm

jin wrote:

@ray

4.2V at 100ma-1000ma

On September 16, 2011 at 9:47pm

jin2 wrote:

4.2V at 100mA-1000mA

On September 16, 2011 at 9:50pm

jin2.0 wrote:

To ray :

4.2V at 100mA-1000mA

On September 17, 2011 at 7:05pm

zz wrote:

Most likely 4.2V, but it is also limited in current.

jin, you misunderstood my question

On September 20, 2011 at 6:48am

Itamir wrote:

Thank you very much. It helps me a lot. Very good material.

On September 21, 2011 at 11:59pm

zz wrote:

Most likely 4.2V, but it is also limited in current.

jin, you misunderstood my question

On September 24, 2011 at 11:23am

zz wrote:

Probably 4.2V, but it is also limited in current.

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jin, you misunderstood my question

On September 25, 2011 at 11:36am

satyendra wrote:

hi evry1..

for my application of voltage(72V) , i connected 23 li-ion cells in series. each cell have 90 AH of capacity.now each and every cells have voltage have 3.3V.

so my question is that how w ould i know that w hat is the current SoC of the cells.

and second question is w hile charging it w hen current starts decreasing, at till w hat point of current i should w ait for the complete charge.

please any1 help me in f inding above.

On September 26, 2011 at 4:20pm

Mark Z. wrote:

Is slow charging (via USB-Port) better then fast charging (w all plug)?

On September 26, 2011 at 8:59pm

Garry D wrote:

I’ve not heard of any entrepreneur but there is a team of scientist at the DOE w ho are on the verge of expanding capacity 8x…

http://w w w .labspaces.net/113675/Better_lithium_ion_batteries_are_on_the_w ay

On September 30, 2011 at 4:04am

Peter wrote:

Great article, helped a lot. Do you have by chance a similar article about proper discharging a Li-ion cell? I’m especially interested in detecting the low er threshold w here discharging

should be stopped. A diagram similar to the one here w ould help a lot. Would you detect voltage? If yes, w hat is the low threshold? Would you detect internal resistance? (If the latter,

how ?)

On October 5, 2011 at 2:06pm

zz wrote:

Probably 4.2V, and also limited in current. Better measure.

jin, you’ve misunderstood

On October 19, 2011 at 10:22pm

tosvus wrote:

I bought a Li-ion battery/pack w ith charger (in the form of an adapter). Unfortunately, I mixed it up w ith another adapter, so I used a 12V-1.5a charger instead of the 12.6V-0.350A I should

have used. I noticed that the battery only outputs 9V max now , w ith charge dropping rapidly. Did I permanently damage it?

On October 23, 2011 at 11:01pm

priya wrote:

hello sir

i w ant to charge a 1.5v cells used in dc pumps

by sw itching it to main supply

On October 24, 2011 at 1:15am

zz wrote:

probably 4.2V, but it is also limited in current.

you misunderstood the question jin

On October 25, 2011 at 7:27pm

Postelle wrote:

Wow , jin is really smart? Maybe she should be the one w riting the articles!

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On October 28, 2011 at 9:52am

Ed wrote:

I have a Toshiba C655-S5056 laptop w ith li-ion battery. Specs say 6 cells, 48Wh. The AC adapter is 65W (19V, 3.42 A). The laptop is dead and I w ant to manually charge the battery to

determine if the problem is the dc jack.

Can I remove the battery and connect it directly to the adapter for an hour to partially charge the battery? I know it’s not safe to leave it connected. I just w ant to charge it enough to

pow er up the laptop for a few minutes before I go to the trouble of replacing the dc jack.

Thank you.

[email protected]

On October 29, 2011 at 1:51am

Tony wrote:

I w ant to use 3 AAA size of these in series in a headphone amplif ier. There is no chemical recombination applicable as in NiCd or NiMH, they are more like capacitors in that w ay. So it

seems they can’t be charged in series. It w ould quickly ruin the low est capacity one. Is this correct? Can you suggest some really simple but safe w ay of charging them, one at a time if

necessary, using only a regulated variable pow er supply w ith constant current limiting, a good quality analogue multimeter (Avometer) and maybe a resistor? I don’t need anyw here near

maximum capacity. Are they easily damaged if the strongest ones reverses the w eakest and therefore should be protected w ith diodes maybe? Can you suggest any good information

about using them in series? Sorry, I should be paying you a consultancy fee for this lot! Thanks.

On November 1, 2011 at 1:45pm

Brian Ahern wrote:

I have an electric car w ith Lithium ion batteries. I have a data logging voltmeter across the 170 volt series pack. When I hooked up the meter after stopping the car it took 2 hours for the

meter to stop jumping all over the place in its voltage readings. After that it became super stable. What is this agitation you are speaking about?

When the sw itch is off and the battery pack is opencircuit no electrons can f low . How ever ion can still f low to equilibrium conditions. Will this look like a slow rise in cell voltage?

On November 14, 2011 at 2:15am

Nitesh wrote:

Dear sir,

I am using the 3.7V/3700mA li-ion battery for my electronic instrument. this battery gets dry after some time. Then i have to remove battery from ckt and directly connect it to the

adaptor(4.1v/1500mA). but that is not possible to do all the time.

Please suggest the solution.

On November 26, 2011 at 10:17pm

Niel wrote:

Interesting article. I have just started using li ion, and the charger I have charges to a voltage of 4.10 volts. I have a lot of experience w ith li po and the charger uses 4.20 volts as the

cutoff for that variety. According to the article, I guess that’s a good idea. I just found it a little unusual. Thanks for the info.

On November 30, 2011 at 6:27am

Terry C wrote:

How can I reset my Li ion 14.4 Hilti battery, peeps say it can be done I only get one single green light and no charge need help on this please, Thank you

On December 4, 2011 at 1:10am

Twoone wrote:

I am w orking w ith an off grid dc motor that requires 48v and 250 ah and i plan for 24 hrs running. I plan to connect to lithium ion battery bank to store energy for later usage. Let say

batteries are in series of 4 it means about 12 v. So how many battery shall i have and w hat is the charger size.? Anybody advise? Tq.

On December 5, 2011 at 11:05pm

voon wrote:

yes i have the same question as ray. my charger specif ications are output 5v, 700mA. My battery is 3.7v 1500 mAh li-ion battery… if i w ant to avoid entering stage 2(saturation charge)

region, at w hat % should i stop charging at? is it 85% w hich is cut off capacity at 4.2 V/cell, or perhaps somew here near 60% w hich is cut off capacity at 3.7 V/cell?

thanks for any help

On December 7, 2011 at 8:00am

Ali wrote:

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Is it better to charge the Li Pp/Li On faster or slow er as I have a variable current charger

On January 1, 2012 at 2:33am

Gary wrote:

I’m having a discussion w ith someone on a forum. It’s going like this:

I’ve got 4 7.4v batteries.

2x1000mah + 2x1200mah

I’m parallel charging them at 8.4v, no balancing at this point.

The charger hits 8.4v and cuts off w hen the current draw drops below a certain point.

My understanding is that each battery w ill saturate at 8.4v line and no further current w ill enter a saturated battery.

He’s of the opinion that I’m probably screw ing up my batteries.

Anyone have some info?

THanks

On January 4, 2012 at 9:22pm

Anand wrote:

Thanks for this w onderful info! really helps

On January 10, 2012 at 4:54am

Asad ali wrote:

Dear,

w hat is the equation to f ind the instant value of charging or discharging of a Li-ion battery ?

On January 25, 2012 at 11:09pm

David wrote:

I have a Lipo battery (11.1V 3 cell / 1100maH) w hich I have a 12V AC adpator to DC charger w ith a amp regulator from 0-4 Amps. Firstly can I charge the battery higher than 1100maH or

does it have to be low er…secondly it has been on for hours at 1000maH but still it doesn’t charge it? What is w rong? Thank you

On January 29, 2012 at 4:26pm

Vince wrote:

Regarding Figure 1: Current is listed as being in Amps (A), but is this a typo? Should it be C, w here C is the number of amps that w ould discharge a cell in one hour? For example, I have

a 3500mAh cell for my Droid phone, so w ould not C equal 3.5A? Is 3.5A then the amount I w ould w ant to use to initially charge my cell until it’s voltage reaches 4.2V, at w hich point the

cell itself w ill determine how much current it draw s?

The article later states “The charge rate of a typical consumer Li-ion battery is betw een 0.5 and 1C in Stage 1”. I w ould LOVE to have that, but can’t f ind ANY! So is this another typo in

the opposite direction? Did they mean betw een 0.5 and 1A instead of C? Because that’s the range most charges seem to max out at.

I have one charger that outputs 300ma (w hich is 0.085C), a few 500ma, and 800ma, and one that does a full 1A, but even that one is only 0.3C. These take TOO LONG to charge my

cells.

To Ryan w ho posted on May 3, 2011, how ’s your project going? That is my need also. I w ill be backpacking for a few w eeks w ith my Droid. I have four 3500mAh cells, and a 10W solar

charger. If 1C for my cells is 3.5A, at 4.2V that w ould be 14.7W, so my solar panels w ill never be able to provide more than the battery should be able to handle. Right??? The problem is

that I can never count on ideal sunlight, so I pretty much w ant to pump everything the panel can generate straight into the cell. How ever, all of my adapters that output 4.2V have severe

current restrictions as I mentioned above, so I don’t think I can get a full charge from the sunlight available. Any advice???

On January 31, 2012 at 7:10am

Dobra Georgian Ionut wrote:

I have a Samsung Galaxy s and please tell me if I use my phone w hile charging the battery is damaging in any w ay. When charging the phone is using charger electricity or battery

electricity ? (the phone has a Li-ion 1500mAh 3,7 V and original charger output 700mA 5V )

P.S. Thank you ?

On January 31, 2012 at 9:02am

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Vince wrote:

No, that is not bad, and sometimes is necessary.

If your draw is less than the charger is putting out, then pow er from the cord is going both to the phone and the battery. But if you are draw ing more than the cord can supply, then the

phone is draw ing from both the cord and the battery.

In extreme cases, the charger may not be able to keep up w ith the draw from the phone, for example if you are providing a w if i hotspot, recording a HD video w ith the light on, and

geotracking your position simultaneously, all w hile trying to sling mad birds at sw ine, your battery may continue to discharge even w hile plugged in, but that’s the only w ay to make it last

as long as possible.

The battery w ill charge fastest w hen phone is turned off because all of the pow er from the cord can be directed to charging the battery instead of also running the phone, but that is not

practical for most people.

Same goes for laptops.

On January 31, 2012 at 9:10am

Vince wrote:

Another clarif ication that I think should be understood: The thing that plugs into the w all at one end and your phone at the other end is not really the charger. The charger is inside the

phone. The w all cord provides 5v to the phone, and the charger inside the phone provides 4.2v to the battery. Although there are (and I have one) actual chargers, w here you take the

battery out of the phone and set it in the charger, w hich plugs into the w all.

The difference is that a charger is (or should be) smart enough to f irst supply a conditioning charge, then a constant current, and f inally a constant voltage, and preferably a shutoff. The

charger in the phone does this. The cord from the w all to the phone is not smart, it just provides a constant 5v.

On January 31, 2012 at 9:41am

Dobra Georgian Ionut wrote:

Thank you Vince ! very usefull ; another question :

I have in my android phone a program that tells me much about battery status and tells me that w hen fully charged is about 4.2 V, above in this article I saw that charging is recommended

under the maximum voltage to extend battery life (w hich you think that is the maximum voltage that the battery should be charged for above recommendation?) the program show s also

battery temperature (w hich you think is the maximum temperature w ould have to be?)

If i’m w atching a movie , or play some games or surf w eb is better for battery to keep phone connected or not to charger ?

P.S. Thank you!

On January 31, 2012 at 10:16am

Vince wrote:

From w hat I’ve learned from these w ebsites, here are the answ ers: First to your last question:

What is really best is to keep your battery around half charged, 40%, 3.7v. So if you’re fully charged, it’s best to unplug it regardless of w hat you’re doing, and if it drops to less than

those numbers, plug it back in.

Tw o things are bad for the battery: First, to let it completely discharge, w hich is almost impossible in normal operation because the phone itself w ill turn off long before the battery is

empty in order to prevent such a thing. The battery itself also most likely contains a similar monitoring circuit, although at a low er threshold. Second bad thing is to keep it at a high voltage

like 4.2v.

Think of it as you breathing. In your normal daily routine, you don’t empty your lungs as far as they w ill go, nor take as deep a breath as you can. You w ork best somew here in the

middle. But if you know you’re going diving underw ater, then you’ll w ant to f irst f ill up w ith as much oxygen as you can hold, so you can stay under w ater for as long as possible. But to

live your daily routine that w ay w ould be very stressful on your body.

Now in regards to your f irst question, and w ith the understanding of the above, no 4.2v is not recommended for extending battery life. 4.2v is a rather arbitrary value that’s been agreed

on by the industry as providing a reasonable balance betw een long term longevity and short term runtime. If you don’t need to survive all day w ithout access to electricity, you’d be better

to stop at maybe 4.0v or even 3.9v. How ever, the tradeoff is that you’ll get few er hours w ithout the charger.

People tend to be less concerned w ith how many years their battery w ill last, than how many hours it w ill last, and w ill often throw out the w hole phone in tw o years anyw ay.

As for temperature, I personally feel that the heat is generated more by the phone than by the battery. Put a healthy battery in a phone and use it hard for a few hours, and the phone

itself w ill raise the temp of the battery, simply because the battery is inside the phone.

Finally, as for w hat the phone app reports, it’s mostly guessw ork (except for temp and voltage). But the voltage is not a reliable indicator of remaining charge, because the voltage can

stay close to 3.7v most of the time. The percentage left is guessed by trying to track and count how many amps the phone is draw ing from time to time, sampling it maybe every few

seconds, and comparing that to the expected capacity of a new healthy stock battery.

On my phone w ith an extended battery, the phone w ill drop to 5%, and then continue to run f ine for another day. So w hile voltage isn’t real accurate, it’s w hat I w atch and I know that

w hen it falls around 3.4v, it’s approaching empty. Then again, if you’ve been using it heavy and let it sit, the voltage w ill come back up a bit.

On February 6, 2012 at 8:30am

David Parkinson wrote:

I have a need to overcharge a Lithium battery until failure. How ever, the charger w e have limits the current as the voltage is reached. What kind of a charger w ill allow me to overcharge

a battery?

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On February 6, 2012 at 9:50am

Vince wrote:

@David, my understanding is that it’s the battery itself, not the charger, that limits the current once it’s getting full. With a typical 4.2v charger, once the cell is saturated at 4.2v, it simply

w on’t draw anything more. Zero current.

In order to force more in, you’ll need to increase the voltage. Maybe you can f ind a 4.3v charger? Or just hotw ire it to 3 fresh alkalines in series, giving you 4.5v. I don’t w ant to be

standing anyw here near you w hen you do this. When you say “failure”, I assume you mean loud noise, smoke and f lames, and lithium shrapnel killing everything around you. You also

could hook it to your car battery. Any DC source of signif icant voltage should cause the catastrophic failure you seek.

Legal disclaimer: Don’t actually do any of this. In fact, forget that I even w rote it. These are bad ideas, and nobody but you w ill be responsible for the consequences.

http://w w w .youtube.com/w atch?v=vS2hGoJVmlA

On February 6, 2012 at 10:11am

David Parkinson wrote:

Thanks Vince ! You are almost correct on the failure scenario (they do burst into f lames, but no real loud noise or shrapnel). This testing w ill be performed in a stainless steel tank for the

purpose of analyzing the gases that are made through this type of failure. We have previously induced battery failure through external heating, case crush and internal shorting. The

next method w e w anted to cover is the possibility of a failure in the charging mechanism that might allow an overcharging situation.

Regards, Dave

On February 6, 2012 at 10:23am

Vince wrote:

@David, ah, glad to know you know w hat you’re doing. I never know w ho I’m responding to, so I often lean tow ard dramatic caution.

But you your goals, a conceivable failure might result from a USB charger somehow shorting the 5v input straight to the intended 4.2v output, resulting in w hat you’re looking for. The USB

out from w all chargers sometimes can supply over an amp.

On February 8, 2012 at 4:28am

b fvb wrote:

yeah men

On February 8, 2012 at 4:30am

Sexama wrote:

-)

On February 15, 2012 at 2:38am

Marios Michaelides wrote:

Just bought a Li Ion receiver battery pack and the istructions say i should plug the balacing plug in the charger, as w ell. The pack only comes w ith one plug, the one the plugs into the

receiver. So how is it possible to balance the cells?

On February 16, 2012 at 4:25am

Juan wrote:

Hello!

I have a question that I have not fully satisf ied by reading this w ebsite.

Using a laptop in a continuosly w ay, is it better to fully charge the battery and then to fully discharge it or is it better to have the charger alw ays connected?

On February 16, 2012 at 10:19am

Vince wrote:

@Juan, the question to your question is “is it better for w hat?” Better for the longest long-term life of the battery? Better for the longest runtime the next time you need it?

In any case, the w orst thing to do is to use it if you don’t need to, to run the laptop off the battery w hen there is AC available. 1.) Batteries w ill last for a few hundred charging cycles.

Fully discharging them and recharging uses those cycles. 2.) If you suddenly need to hit the road, you w ill only have a partial charge.

The best thing to do for the longest runtime w hen you need it is to keep it fully charged. How ever, this w ill reduce the long-term life expectancy of the battery.

The best thing to do for the long-term life of the battery w ould be to charge it to 50%, take it out of the laptop and don’t use it, and just run the laptop on AC. Recheck it every few months

to keep the charge around 50%. If you are planning a trip, then put it in and top it off before you go. But this all seems a little inconvenient.

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So the bottom line is that you’ll have to choose a balance betw een long-term, short-term, and convenience, based on your ow n personal goals.

On February 16, 2012 at 2:16pm

Juan wrote:

Well Vince, thank you for your reply.

My question w as….better for longest long-term life of the battery.

I mean if you have to w ork w ith battery on because you need to move in the off ice you cannot put and take off the battery every time.

I read about someone that think it is better to charge the battery and then take off the charger to let the battery discharge and then re-connect the charger and more over!

Instead some other one assure that is better to leave the charger alw ays connected to also get the battery alw ays balanced…

I don’t know …you reply is quite clear and I know the better w ay is to not use the battery but I’d like to know your reply in this scenario.

Thank you.

On February 16, 2012 at 3:58pm

Vince wrote:

@Juan, yes, in your case I recommend plugging it in w henever convenient. There is no advantage to unplugging it for the purpose of intentionally discharging the battery. That only hurts

it.

Remember that the pow er cord is not the charger. The charger is inside the computer, and it w ill stop charging the battery w hen the battery is full, even w hen the pow er cord is still

connected. At that point the computer is running AC, not the battery, and it w ill take a long time before the battery drops low enough on it’s ow n for the charger kick back in again. But

w hen that happens it w ill quickly top off the battery again, and you probably w ill never notice it sw itching. So the battery w ill alw ays be kept very close to full, so it’s ready w hen you do

need to use it.

On February 17, 2012 at 12:54am

Juan wrote:

@Vince: thanks for your answ er. I know the charger circuit is in the laptop…It’s just the name w e usually give to it.

Your answ er let me get a question too: If the charger stops to charge the battery and the computer w ill run AC for a w hile, w hy in the article is mentioned that the battery can reduce its

life because to some chemical effects.

What do you say about this aspect?

Thank you very much

On February 17, 2012 at 7:00am

Vince wrote:

@Juan, I’m not sure I understand your question correctly, but if I do, this is my answ er:

Keeping the battery at full capacity does reduce it’s life because of the internal chemical stresses it suffers at high capacity. But this is how most chargers are designed. This is the

tradeoff, the dow nside to being prepared for maximum run-time.

Batteries are most comfortable at half capacity. This is w hy I say it w ould be best to charge to 50% and then remove the battery if you know you w on’t be needing it for a long time,

because the chargers are not designed to stop and leave it at 50%.

On February 19, 2012 at 3:30pm

Juan wrote:

Well the question w as a little different but that’s ok about your answ er.

Thank you very much.

Bye bye.

On February 21, 2012 at 3:12pm

Sapan wrote:

How does this apply to an iPhone? If I w ant to maximize the life of the battery should I charge approximately to 75% then let it drop to 25% and then keep repeating?

On February 21, 2012 at 3:13pm

Sapan wrote:

And w hy does apple recommend draining your battery completely at least once a month? http://w w w .apple.com/batteries/iphone.html

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On February 22, 2012 at 9:38am

Vince wrote:

@Sapan, I’m sure the info on this site w ould apply to all Lithium-Ion cells, including those used by an iphone.

Yes, your 75% to 25% sounds good, trying to keep it around half w ay.

Their recommendation to completely drain it monthly makes no sense for getting the most out of the battery, but it may be useful for calibrating the phone.

Over their lifetime, the maximum useable capacity slow ly decreases. By periodically topping it off and letting it run dow n to w here it turns itself off, your phone can learn w hat the new

capacity is, and thereby giving you a more accurate percentage remaining indicator.

Phones have no w ay of know ing or measuring how much charge is really left, because the only measurable value of the battery is voltage, and as you can see from the charts at the top

of this page, the voltage can stay around 3.7v for a very long time and then drop to dead very suddenly. So w hat they try to do is keep a running total of how many milliamps w ere draw n

over frequent small intervals. It’s kind of like a printer trying to estimate how much ink is left based on how many pages you’ve printed since installing the new cartridge. Not real

accurate, but it’s the best it can do.

So by topping it off and then running it to completely dead w hile the phone counts how much it’s using every second, it can get a pretty good idea w hat the total expected capacity should

be, and use that info to calculate a percentage remaining.

On February 22, 2012 at 2:14pm

Georgian Dobra wrote:

Did someone now some tips for charging unused and new li-ion batteryes ?

I recently bought a new 3,7V ,1650mAh samsung battery for mai GALAXY S , I’ll w ait your answ er before f irst battery use.

Also the old battery (1500mAh) it’s in a good condition (not even 30 charge cycles)

, do you have some advices for preserving and alternative use uith the new one ?

THANK YOU !

On February 22, 2012 at 9:26pm

Vince wrote:

@Georgian Dobra, Advice: charge it and use it.

I recommend an external slow charger. I just ordered another from ebay for under $3. Initially charge new battery for 12 hours. Then each morning, simply sw ap the freshly charged

battery into the phone, and place the other battery into the charger. Repeat each morning, and you may f ind yourself free from charging cables!

Slow charging over night provides a deeper, more saturated charge, by skipping stage 1 (as depicted in the initial graph on this page) and going straight to stage 2. Admittedly, charging

this fully is not optimal for long-term longevity, but gives the best run-time w ithout overcharging.

On February 23, 2012 at 10:29am

Dobra Georgian Ionut wrote:

thank’s Vince for your fast answ er !

unfortunately I am from Romania (East of Europe) and I don’t have ebay . Ofcourse there are some alternatives foe ebay in my country but those are much expensive then ebay. Even so I

might f ind this kind of charger but w hich is the optimal amps w hen you say slow charger (also as an alternative I can use a normal w all charger used for a bluetooth headset <550mA ,

4,75 V> ; is this a good idea ?)

some advices for my actual circumstances ?

Yet I am counting on using larger capacity battery and the oldest only in rare cases…

thank you again !

On February 23, 2012 at 11:24am

Vince wrote:

@Dobra Georgian Ionut, No, 4.75V is not a good idea. Too high. Besides, how could you connect that to your battery?

The charger of w hich I speak accepts the battery directly. The manufacturer’s w ebsite is w w w .yiboyuan.net. Everything there is in Chinese, but you can see pictures.

My charger came w ith a 3500mAh battery. In my case, the C value is 3500mA, the amperage at w hich a full battery w ould be drained in one hour. My charger output is 350mA at 4.2V,

w hich is 0.1C for my battery. This is slow , and it takes about 12 hours for a full charge from dead.

If you can see this w ebsite, it is a picture: http://ecx.images-amazon.com/images/I/41JPn8azc4L._SL500_AA300_.jpg

On March 10, 2012 at 1:38pm

CXR wrote:

Hi Vince,

I’ve been reading some blogs on your site. Super informative!!

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I have some questions of my ow n RE Li ion EV batteries. I have done my research & believe I understand to be true, Li ion EV batts like to be kept at a 50-85% state of charge (SOC). If

this is true then I also believe to be true the Li ion EV batt w ill last quite a long time.

1. Is a trickle charge an appropriate w ay to keep the Li ion EV batt at the nominal 50-85% SOC?

2. Is 4.20V DC the nominal voltage to make this happen or is it better to use a 4.00V DC or low er?

3. Can this be managed , i.e., w ith the old 1960-65 generator and voltage regulator automotive setup w here the ICE auto-engine ran a generator and a regulator w as used to keep the

battery charged to optimum volts/amps, i.e. only?

4. What voltage/amperage w ould be best to provide to a Li ion EV batt to keep it at this 50-85% SOC, happy area , if the EV batt is using 4.2V cells, as many as 6000?

Thanks in advance for responding,

CXR

On March 10, 2012 at 5:33pm

Vince wrote:

@CXR, Thanks for the positive feedback. Unfortunately, your questions are beyond my area of know ledge. I even had to look up w hat “EV” meant!

I hesitate to discuss things if I don’t know w hat I’m talking about, but if I may speculate and extrapolate w hat I’ve learned, and apply it w hat I’m guessing an EV might be, that being just a

large battery of Li-Ion cells…

1. I don’t believe there’s such a things as “trickle charge” regarding Li-Ion cells. You simply set the voltage, and the cells draw w hat they can. As they become saturated at that voltage,

they just w on’t draw any more current.

2. 4.2v is generally considered to be 100% capacity. 3.7v w ould be 50%, the “nominal” voltage. Because it’s not a linear transition, I think your 85% goal might even be achieved at 3.9V.

I’m just guessing based on discharge charts I’ve seen.

3. You’re over my head.

4. I don’t think there’s such a thing as a 4.2V Li-Ion cell. The current norm is 3.7V (nominal) for cell phones, w hich have a non-linear runtime voltage betw een 4.2 and 3.2V. As for your

maximum current, you’ll need to do a little math. First you need to know the capacity of each cell in mAh, then multiply by the number of cells in your battery. For example if I w ere to use

four cells each rated at 3500 mAh, I’d have C=14A, the current at w hich the battery pack w ould be depleted from full to empty in one hour. Next you need to know the manufacturer’s

maximum recommended charging rate. If it’s 0.5C, then I’d w ant to charge at no more than 7A.

Now that’s all assuming that your battery pack is w ired in parallel, w hich is probably not the case. If your 6000 cells w ere 600 parallel packs of 10 each in series, then your 3.7V nominal

becomes 37V.

Bottom line is that I’m not qualif ied to answ er your question. Your specif ics w ill depend on many variables I’m not familiar w ith. How ever, my guess w ould be that by charging 6000 cells

from a household outlet, you’ll probably never come close to the maximum charging current.

On March 11, 2012 at 6:25pm

CXR wrote:

Vince,

Thanks for getting back so quick. I’ll make an attempt to simplify.

1. An EV = Electric Vehicle.

2. Trickle charge is generally not regarding Li ion batteries, yet, if you w ould humor me,

RE “set the voltage” , If the voltage is set at 4.2v - 3.7v and stays constant for 6-8 hours

intermittently w ill this charge the battery, if the battery is f irst fully charged ? .By intermittent I mean 3 hour at 4.2v , 3 hour at 3.7v , 1 hour at 4.2v.

3. RE “Over your head” the scenario in # 2. above, is w hat I am describing. Just trying to understand if I can , or need to start or stop the charge automatically. (Voltage Regulator)?

4. I am not speaking about a cell phone or a small battery. Please think EV.

Manufacturer recommended charge rate is not w hat I am thinking. I am thinking if I can keep the Li ion battery charged w ith a trickle after an initial full charge

5. I w ill hunt dow n the ,” 6000 cells in parallel or series and /or bundled” and see if I can f ind this info to give you a more intelligent basis to answ er.

Thanks,

CXR

On March 11, 2012 at 6:44pm

CXR wrote:

Vince,

Just found the info on parallel/series.

For the Li ion batt I am speaking about a full re-charge requires 3,5 hours at 70 amps, 240 volts.

This battery w hen fully charged stores approx. 53 kWh at a nominal 375 volts.

I think this may help you and I w ith the calks you are trying to teach me.

Thanks

CXR

On March 11, 2012 at 6:54pm

CXR wrote:

Vince,

I left out some important info.

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6000 cells are arranged into 11 sheets connected in series. Each sheet contains 9 bricks connected in series. Each brick contains 69 cells connected in parallel.

Cells are the 18650 type found in laptops.

Thanks

CXR

On March 11, 2012 at 9:58pm

CXR wrote:

Vince,

What is meant by “the absence of trickle or f loat charge at full charge” RE a Li ion battery.

This comment is from the Battery university article “Charging lithium ion “

Does it mean that a Li ion batt can use a trickle charge w hen it is not at full charge?

OR

Does it mean that a Li ion batt cannot use a trickle charge at all , anytime?

Thanks CXR

On March 11, 2012 at 10:23pm

CXR wrote:

Vince ,

I think I may have found my answ er. please see same article as above Charging lithium ion

Section 1 paragraph 17 second to last sentence, “Charge absorption is very high and w ith a low and intermittent charge ,charging simply takes a little longer w ithout negatively affecting

the battery. The absence of trickle charge further simplif ies the charger.”

Question

1. What is a low and intermittent charge ? below 4.2V ?

2. What is meant by “the absence of a trickle charge?’

3. Can I put , w hat I call a trickle charge, of 3.7DC-4.2DC w ithout harm to the battery in a

“low and intermittent charge” format?

Thanks

CXR

On March 12, 2012 at 11:08am

Vince wrote:

@CXR, thanks for the clarif ications. The sum of my know ledge about electric vehicle batteries is from w hat I just learned from you.

So if you’re talking about a battery consisting of thousands of cells, and the battery has a nominal voltage a hundred times higher than that of any cell, I can’t imagine w hat you’re

considering using 3.7-4.2v for.

Since the battery is nominally 375V, and it takes 240V to charge it, then the 240V (I assume AC) is pow ering a dedicated charger, not charging the battery itself.

If w e just scale the numbers from a normal Li-Ion cell up by a hundred fold, simply as a thought experiment, maybe your 85% goal w ould be achieved at four hundred volts DC. Once the

battery pack is saturated at that voltage, the charging current w ould be zero. But all batteries have some self-discharge, plus Li-Ion usually have some monitoring circuitry, so your real

“trickle” current w ould probably be equal to w hatever the total self discharge current w ould be.

THOUGHT EXPERIMENT ONLY! The info I provide should only be used for thinking about things, not actually doing anything at all.

On March 12, 2012 at 11:13pm

CXR wrote:

Thanks Vince for your help !!

i’ll be back at you in the future, i am sure.

CXR

PS don’t be a stranger , if you f ind something you feel may help me send me an email !

On March 30, 2012 at 10:38am

Blake Cooper wrote:

As alw ays, a w onderful post, full of great information that w ould otherw ise not be readily available. I’m sure I’m not alone in saying that Battery University has been a great help in my

professional and hobby lives!

On April 4, 2012 at 5:00pm

Hanyu Liu wrote:

I feel so lucky in reading this article.And I’m interesting in the charging methods used in USA,Germany and other developed countrys. If you are convenient,please tell me the research

status about some developed countrys.Thank you ! Thank you !Thank you !

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Thank you ! Thank you ! Thank you ! Thank you ! Thank you !

On April 13, 2012 at 4:07pm

Damian wrote:

Hello,

just bought a brand new MOTOROLA RAZR XT910. It has an (incorporate) Standard battery, Li-Ion 1780 mAh.

For the best performace how should I do the f irst charge? Phone turned off and 12 H of charging? Do I need to repeat this the 2nd and 3rd time?

Many thanks!

On April 22, 2012 at 2:54pm

Christophoros wrote:

Hi

I disconnected the old 11.1dc Li-ion laptop battery and remove all the 6 cells from it (Note:i removed w hen the battery w as discharge)

I have connect 3 in series (i get 10.5VDC) and also the other 3 in series (i get also 10.5VDC) and f inally the 2 packs in parallel for longer runs.

So 10.5+10.5 in paraller=10.5VDC

The question….How do i charge them? What transformer shall i put?

On April 25, 2012 at 6:18pm

Ace wrote:

Hi,

I have an application w here I’ll be using Lithium Ion Phosphate batteries in the Antarctica in -40 deg C temperatures. Normal charger voltage is 3.65V per cell. Would I have to increase this

CV?? if yes then by how much.

On May 2, 2012 at 7:01pm

wazzink wrote:

i salvaged a laptop battery and got a lithium-ion battery pack and i threw aw ay the circuit before i did my evil laugh..

now i got 3 pairs of parallel 18650 batt connected in series w ith 10.8v nominal and rated 3.2AH.. w hen fully charged reaches 12.6v

i hope you can imagine the config. w ell it looks like this |=|=|=|

my questions are:

1. Can i use a charger w ith 12v and 1.5A max to charge the w hole pack??

2. What if i use a max 1A?? max 500mA??

3. Does the charging current automatically drops as the batt pack reaches 12v??

4. I’m planning to use LM317T or LM7812 for the charger and charge the pack for max 3 hours.. is it ok??

..tnx!!!

On May 2, 2012 at 7:20pm

Vince wrote:

@w azzink:

1: probably

2: slow er, better charges

3: yes. Current f low s from higher voltage to low er voltage, like from a tall bucket into a shorter bucket. Once they are the same voltage, current f low w ill stop, or reduce to the rate of

parasitic self discharge. Essentially, trickle charge.

4. don’t know about model numbers, but since 12v is less than 12.6v max, I w ould think it should be safe to leave it hooked up there indefinitely.

One w ord of advice: I’ve read w arnings against building your ow n battery packs, because all cells must be balanced, or one w ill discharge faster, go negative, and then bad things start

to happen. But in theory, yes I think it should w ork like you plan.

On May 2, 2012 at 8:13pm

wazzink wrote:

@vince

thanks man!!! got a fast reply, i thought i’ll be checking this site next w eek.. thanks

i didnt touch the connection of the batteries, already in that setup w hen i took it out from the batt pack.. only i threw aw ay the protection circuit..

the brand is panasonic CGR18650HM.. is it good one??

w hat should be the f inal charging current before i disconnect it from charger??

LM317T and LM7812 are voltage regulator ICs w ith max out current of about 1.5A..

thumbs up to you dude

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On May 2, 2012 at 10:07pm

Vince wrote:

Sorry, can’t tell you if panasonic CGR18650HM is good. No idea.

Regarding f inal charging current: The value referred to as “C” is the current at w hich the battery w ould fully deplete in one hour. In your case, C=3.2A. According to the f irst chart at the

top of the page, batteries can be considered full w hen the charging current falls to 3% of C, or about 0.1A in your case.

On May 3, 2012 at 3:44am

wazzink wrote:

thanks Vince!!!

I’m so lucky i found this site f irst before i can make a bomb..

i think i’ll cut it off in 200mA for more safety..

thanks dude..

i found 2 devices attached on one side of the batt pack w hich i didnt remove..

one is,i think, for temperature sensing,..and the other one connected in series in +terminal and i dont know to w hat use it is but i dont w anna take it off.. i am thinking if the second part has

something to do w ith current limiting so im planning to keep it there..

i googled the part no. 4MM80H1-19 but no info found..

SALUTE to you man!! very big help..

On May 3, 2012 at 9:12am

Vince wrote:

Glad I can help. I don’t think you need to w orry about safety at the ending current. Since you’re only charging at 12V instead of 12.6V (divided by 3 w ould be 4v vs 4.2v, w here 4.2

w ould be considered “full”), you’re never charging to full capacity anyw ay. Slow er charging is better than faster. The voltage is the safety issue, and 12v w ill be great for safety and

also longevity of the battery. I think the cutoff at 3% is more simply because there w ouldn’t be much advantage to keeping it charging beyond that, as it’s already just about saturated. My

chargers only charge at 350ma max, and yeah, they take all day.

On May 9, 2012 at 5:25am

Walter Baeck wrote:

Wonderful site ! Thanks for this very clear explanation.

On May 25, 2012 at 2:38am

maksud wrote:

I have one question that if i give 12Vdc charging to 6Vdc Li-ion battery directly then w hat w ill happen to battery? w hich effect may be seen? . If something happend to battery then I need

some mathematical prove. thanx. I need answ er urgently

On May 29, 2012 at 8:51am

Mar wrote:

Some clarif ication please

1) How could an over-discharged single 3.7v Li-ion battery be “boosted” to life again? Having this is battery specs ( US18650gr )

Nominal Voltage Average 3.7 V

Nominal Capacity 2200mAh, Minimum 2150mAh

Max. Charging current 2.2A Max.

Max. Discharging current 4.3 A max.

2) Could I use the basic 5Vdc /800ma Nokia cellphone charger w ithout any modif ication for boosting?

3) Is it better if the voltage is low er than 4.2V dc for safety and other concern?

On May 30, 2012 at 6:53am

Ron wrote:

Hi Mar,

#1. Depending on the battery some w ill have a tiny plastic label covering a set of electrical contacts that must f irst be briefly shorted w ith something such as a paper clip. This resets the

electronic safety device installed in the battery itself. From there you should check the voltage on the battery before charging it. If it reads 1.6 volts DC or less then toss it in the garbage

simply due to the fact that the battery may be unstable from this point on. Other than that placing it on a charger and checking the voltage after a few minutes to see that it is charging is a

good idea.

#2 I am unfamiliar w ith those chargers

#3 At 4.2 volts you do get a greater amount of charge into your battery than at a low er charge voltage, the only risks are to battery life expectancy due to the fact that your battery is

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approaching it’s maximum safe voltage point (4.3v is really bad), but then again temperature, rate of charge, and the average charge state of your battery w ould also be factors that

w ould diminish your battery’s life expectancy. So going to only 4.0vdc on a charge but doing it on a fast charge and keeping your battery on full charge for vast amounts of time w ould be

w orse for the battery life expectancy than a modest amperage 4.2 volt charge rate.

On June 1, 2012 at 1:14am

Richard wrote:

Hi

I have a 24V 10Ah Li-ion battery that I w ant to charge w hilst on a boat. I have no details about the boat as w e are unsure w hat boat w e w ill be using.

My questions are

1 How much current w ould the bike take w hen charging?

(I need to know this so that i know w e are not draining the boats pow er w hen not hooked up to the shore pow er)

2 What size inverter w ould be needed?

If you can reply as soon as possible that w ould be fantastic.

Many Thanks

Richard

On June 1, 2012 at 12:36pm

Pantaz wrote:

1. Are any chargers able to determine “C” for individual cells? (So that they can adjust charging rate for different capacities.) Is it even possible, in any practical w ay?

2. I’m building bicycle LED headlights, and I w ant to experiment w ith different cell combinations and capacities in series/parallel configurations. When charging a parallel battery pack,

should/can the charge current be increased proportionally? (E.g., “C” for tw o 2200/mAh cell in parallel = 4.4A, so a C/10 rate w ould be 440 milliamps?)

On June 1, 2012 at 2:37pm

Vince wrote:

@Richard,

I can only assume certain things based on your question. You mention a bike? Maybe you have a rechargeable electric bike? For your answ ers, I w ould look at the charger that came

w ith it. It should list the current it w ill draw . You mention inverter, so I assume your bike charger runs on 120V AC, and your boat has 12V DC like a car? If this is the case, then you are

trying to convert 12V DC into 120V AC w hich probably has an adapter to convert it back to DC, probably 24V DC. You may w ant to see if you can f ind, possibly from the manufacturer or

elsew here, a different type of adapter. Also, assuming a boat is like a car, there are fuses that may limit your charging current anyw ay.

On June 1, 2012 at 2:46pm

Vince wrote:

@Pantaz,

1.) I don’t know how a charger could be able to know the capacity of the battery, unless it is perhaps a conditioning charger that fully discharges, fully charges, and fully discharges

again to measure it. Since this is not necessary for Li-Ion, I haven’t seen any that do this, like they used to do for NIMH and NICD. How ever, That is exactly the process some people

recommend for cell phones to calibrate the battery monitoring softw are. As far as I know , that information is only used to display the % remaining symbol.

2.) Yes, that sounds correct.

On June 9, 2012 at 7:02am

Enrico IK5DFD wrote:

For reduce output voltage of little charger I can suggest to put in series a silicon diode for a voltage drop of approx. 0,7 V (1 N 4401-7) a german diode( more rare) for drop approx 0.4 V.

On July 3, 2012 at 12:35pm

A-Freak wrote:

Hello to the Battery Experts

I w ant to build some kind of portable “Pow er Block” w here an solar paneel keeps some paralell connected Li-Ion cells (at least 10Ah) charged. It should deliver approximately 100mAh for

some LEDs every night and as much capacity as possible w hen needed a few times per year.

Most important is the longest possible life w ith respect to remaining capacity. It needs to be available for at least 5 years w ithout service, better 10 or more.

It is clear to me that i loose capacity but gain lifetime w hen i charge an Li-Ion cell to less than 4,2V so i w ould like to do this. Additionally charging current w ould be very slow , at least tw o

sunny days for recharge and much more w ithout sunshine.

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Now my question is:

Do i still need some kind of charge termination for this application or w ould the cells stay happy w hen i just recharge them up to maybe 3,9V and keep them floating there?

On July 3, 2012 at 6:59pm

jacky wrote:

I ow n a Htc Sensation XE,

So as u said that 4.2V to charge the battery,

But w hy the original htc charger output w as 5V___1A ???

Since i saw the article said the battery cannot charge more than 4.2V.

On July 4, 2012 at 7:36am

Vince wrote:

@A-Freak,

It’s my understanding that current can only from from higher voltage to low er voltage, so if your charging voltage is 3.9V, current f low w ill simply stop until your battery pack drops below

the charging voltage. Therefore, no, I don’t see any need for any type of charge termination.

If your battery voltage goes above the charging voltage, then current could reverse, backfeed into the charger, and drain the battery pack. This could happen in tw o situations: 1) it’s

cloudy or night time, and the charging voltage drops below the battery voltage, and 2) battery voltage can raise and low er w ith environmental conditions. I recently noticed this w ith my

ow n cells w hich w ere left outdoors, not attached to a charger or anything.

On July 4, 2012 at 7:48am

Vince wrote:

@jacky,

Good question. This is a common misconception because even many of those w ho know better still use in the common, rather than the correct, w ay.

The 5V 1A thing you are referring to is not the charger. It is the thing that provides pow er to the charger. The true charger is built into the phone. The thing you see is just providing high

current USB type pow er to the charger. It’s quite generic, and can be used to pow er anything that takes 5V, up to 1A, including USB pow ered coffee cup w armers, etc. The charger in

the phone, on the other hand, w hile being pow ered by 5V and draw ing up to 1A, most likely has monitoring circuitry, shutoff, and other smart sensing stuff. It needs 5V to run itself and

to output 4.2V. The 5V pow er source has none of that.

On July 5, 2012 at 6:30am

jacky wrote:

@Vince,

Thank for the reply,

This is the great information. I think u can make w rite this statement to your w ebsite, so everyone can read 1 more useful information about the USB adapter charger and inside the phone

charger.

Thank you.

On July 6, 2012 at 1:30am

manoj wrote:

i w ant battery for instant of pow er charging and w hen the circuit sw itch is closed it w ill provide continuous supply and the range is around 12 v

On July 12, 2012 at 7:42am

crs wrote:

I have a razor w ith a Li battery. Its w all charger is rated at 4.2v 600ma, but I’d like to build an adapter so that I can charge it from USB (5V +/- 5%). Could this be done by adding one or

more diodes to drop the USB voltage dow n to 4.2V?

On July 12, 2012 at 9:09am

Vince wrote:

@crs, I think it’s more complicated then that. Here are some ideas (w hich are above my head):

http://w w w .maxim-ic.com/app-notes/index.mvp/id/3241

http://w w 1.microchip.com/dow nloads/en/appnotes/00971a.pdf

On July 16, 2012 at 10:17pm

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krist0ph3r wrote:

props to you. excellent article. exactly w hat i’ve been looking for, for years!

On July 17, 2012 at 1:27pm

Sally ahmed wrote:

Hi

I am trying to fabricate Lithium ion batteries but I am not getting the voltage it should reach

Materials are (LiCoO2 Cathode, LiPON solid electrolyte and Ni as the anode)

Theoretically speaking, the voltage should reach 4 or 3.9 V but in my case, it doesn’t go beyond 1.5 “saturates there”, then it gets self-discharged in few minutes

Do you have any idea w hy i am not getting the 4 V?

Thanks alot

On August 1, 2012 at 6:16am

Kingsley wrote:

thanks guys. there’s an unfathomable w ealth of know ledge from this resource. keep it up @ Isidor

On August 7, 2012 at 9:46am

Michael Bernardo wrote:

Thank you for the article! This clears up a lot of the myths going around.

On August 9, 2012 at 6:49pm

Terry Wolbert wrote:

Anyone had experience w ith a “cell” reversing it’s polarity/ ; and how to get it ‘reversed” ?

On August 22, 2012 at 6:38am

kamal wrote:

i w ant to learn about battery

On August 22, 2012 at 7:53am

Dan wrote:

Hi All

I noticed above this statement:

“If the discharge continues to about 2.70V/cell or low er, the battery’s protection circuit puts the battery into a sleep mode. This renders the pack unserviceable and a recharge w ith most

chargers is not possible. To prevent a battery from falling asleep, apply a partial charge before a long storage period.”

I have found this to be the case in a system I am designing, as the battery protection circuit releases the battery from sleep mode w hen a certain voltage is presented across the

protected battery terminals, and since my charger IC uses current, it w ill not cause the protection IC to release the battery from sleep mode.

My question is, how do prevent the battery from going into sleep mode in my system, I have a circuit that shuts off all of the circuitry at about 2.9V and then the system current reduces to

about 6 microamps, but over time, this small draw w ill eventually low er the battery voltage to a point w here the battery charger w ill not be able to bring the battery out of sleep.

How do I handle this in my product? Is there a special kind of charger IC that w ill cause the protection circuit to release the battery, or do i simply have to tell my end users not to leave

their system uncharged for extended periods of time?

Thanks so much,

Dan

On August 22, 2012 at 9:29am

Vince wrote:

Hi Dan,

I think even w ith a totally disconnected battery, the battery’s ow n internal circuitry w ill eventually self discharge it into the “sleep” mode. I think a cell w ould have a shelf life for a “long”

time, but not indefinite, so no user should ever leave anything uncharged for extended periods. I don’t see any w ay around that.

Vince

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On August 22, 2012 at 9:37am

Dan wrote:

Thanks Vince,

I w as leaning tow ard that possibility after reading numerous articles and such as w ell.

Does anyone know how to calculate the amount of time it w ould take a battery to discharge from a particular voltage to a different voltage. Say discharge from 3.00V to 2.55V w ith a

know n current draw , for example 6 microamps? or at lease a decent estimate?

Thanks,

Dan

On August 23, 2012 at 9:54am

Vince wrote:

No, I don’t think so. The problem is that lithium ion cell voltage doesn’t drop in a linear fashion. This is actually it’s strength, that it can maintain close to its nominal voltage throughout most

of its discharge cycle. Because of this, w e can’t really estimate how much charge remains, based on a voltage reading. My only experience is w ith my cell phone, but it estimates

remaining charge by trying to tally up, second by second, how much charge it has used, and then subtract that from the assumed maximum capacity.

On September 4, 2012 at 11:51am

Alex wrote:

I have a bike light battery w hich is labelled ‘Rechargable li-ion 7.4v’. I have lost the charger but I have an AC adaptor labelled ‘PRI: 230v ~ 50hz, SEC: 4.5v - 200ma.

It f its the light battery.

Could I use it to charge the light battery?

Thanks!

Alex

On September 4, 2012 at 4:15pm

Vince wrote:

Hi Alex,

No, I don’t think so. I suspect your 7.4v is actually a battery of tw o 3.7v cells, 3.7 x 2 = 7.4.

So if a 3.7v charges to 4.2v, a 7.4v w ould probably need 8.4v. Just guessing.

Vince

On September 5, 2012 at 1:25pm

Alex wrote:

Vince.

Thanks for your reply. I’ll invest in the correct replacement charger.

Cheers!

On September 10, 2012 at 10:18am

SinthiaV wrote:

@crs @Vince Hi. The w ay to drop a voltage is to put the circuit in question in series w ith a resistance. In order to determine w hat size of resistor to use, you use the series property that

the voltage drops across the components in a series circuit add up to the source voltage. Measure the impedance across the outputs of the existing circuit. By applying ohm’s law (v/i=r)

you should see 4.2V / .6A = 7ohms this w ill be r1. The resistor is r2. v1 and v2 are corresponding voltage drops. Since current is equal at all points in a series circuit, w e can ignore it and

say r1/r2 = v1/v2 for a result of r2=1.3ohms.

There w ill be a drop in current , how ever at 1.3ohms I think it w ill be small. If I remember right (DC theory w as a long time ago!) it w ill be proportional to the size of the resistance.

On September 18, 2012 at 9:09am

nicholas finch wrote:

Some good information on here, w ell done to all those w ho have contributed.

I have a very technical question that I am trying to solve.

I am w orking on an EV Motorbike project, and at the stage w here w e have selected the batteries, and are trying to make out ow n charging and Very basic BMS system.

I have 30 x LiFe batteries at 60AH each - w ired in series.

We are thinking of placing Relays on each individual cell ( 30 of them ) that w ill remove the cell from the series, and reconnect the series for the other cells, thus isolating the individual cell

w hen ever an overvoltage or undervoltage level is reached.

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For the DC motor operation this is f ine - as voltage drops, then max speed drops, and is of no concern to me.

For the Battery charging how ever, as they are in series, I w ill need 30 x 4.1V DC = 123 Volts to charge the entire series, and probably something like 10 - 20 Amps.

As a cell is taken off line w hen or if it reaches say 4.1 volts. I need to either absorb the

extra 4.2 Volts, or reduce the charge voltage to 118.9 Volts, and so on and so on.

Now … does it make sense to charge them this w ay?

Is it possible to drop the voltage of a charger from a signal w hen cells are taken off line?

or w ould it make sense to add in a resistor to the series to soak up the extra 4.1 volts ( 1 resistor per battery until they are all off? )

Or should I try and make individual charging of each cell using linear voltage regulators such that each cell has it’s ow n regulator, and if 1 is taken off line, the others should still charge at

the same volts ?

Parallel charging is out of the question as this w ould need massive current. to be normal time… 60 AH cells x 30 = 1800 Amps, so C/100 is still 18 amps, and it w ould take 100 hours to

charge. .... too long!

On September 24, 2012 at 5:11am

Richard Goodman wrote:

I have made up a battery using four 10 AH 3.6 volt LiPo cells. I use these to pow er a transceiver w hich requires no more then 15 VDC. All 4 cells in series actually provides 16.8 VDC ...

too much for the radio. I have added a sw itch to bypass one of the cells w hile the battery has a full charge. This allow s me to run the radio at 12.3 volts. When the battery voltage drops, I

sw itch in the bypassed cell. By doing this I am unbalancing the pack by discharging 3 cells more then the remaining bypassed cell. I charge the battery using a smart charger at a rate I limit

to no more then 1 amp. I do not monitor each cells voltage individually. If I charge all four cells in series and that one cell is at a slightly higher vol;tage then the others, w ill they eventually

equalize or w ill there be long term damage?

On September 29, 2012 at 7:58pm

MARK WILSON wrote:

Great questions from both Nicholas Finch and Richard Goodman. Unfortunately, I say this NOT because I have any answ ers, but because after reading this entire page, I have very

similar questions. I am building a 72 volt battery pack for my ebike. I am using 18650 laptop cells. I have simply removed the 12 cell / 10.8 volt packs from each casing. I am soldering the

leads in parallel and series to achieve a pack w ith 72 volts (or fully charged at 4.2 volts per cell to 75.6V). Pow er capacity w ill be immense and provide crazy riding range w hile being w ell

w ithin the c rating for such cell chemistry. As a result of reading this very informative w ebsite, I have learned that I w ould greatly gain cycle life by charging to low er voltage. I w ill

charge to only 72volts as I can easily sacrif ice batt. capacity/range in exchange for a healthier battery. My question regards cell balancing. Is a BMS VERY necessary? If I keep the pack

to mid-range capacity use (being conservative in both charge cutoff and discharge cutoff) can I get aw ay w ithout one? Will the entire pack balance itself if given time to “rest” after

charging to 4.0 volts per cell? Would such a pack have greater potential for damage if charged to full potential or allow ed to drop to a normally acceptable low voltage due to some

unbalanced cells dropping too low ? AWESOME

SITE! thank-you.

On September 30, 2012 at 8:11am

nicholas finch wrote:

Hey Mark, I can answ er some of your question.

If you w ant the batteries to last longer, you need to charge w ith less current at a slow er rate. If the voltage of the charger is too high, the batteries overheat and blow up, rather than not

lasting a ” reasonable” time. Your charger should charge at no higher than 75.6 volts, and current should be limited to the Total cell AH current divided by 5 or 6. This w ill give a 100%

charge after 5 or 6 hours. If you low er the voltage to 72, and charge w ith more current ( ie your charging the battery faster ) it w ill not last as many cycles, and also, w ill not reach full

capacity.

If you don’t have a simple bms, the problem arises that one cell w ill reach full before another has reached full, and vice versa, The BMS’s normally balance the charge by reading the

voltage, and w hen a battery is reading over 4volts during charging, a resistor is added in parallel to the battery and charger, to reduce the charge on that cell, w hile charge on other cells

catch up. that is how balancing is achieved.

If you diischarge one cell before the others, and go below your cutoff cell, that cell w ill start getting damaged, and if you go to the extreme, current w ill f low backw ards in it and it w ill melt,

and probably take dow n other batteries w ith it.

hope that helps w ith

some ideas

nick

On September 30, 2012 at 8:15am

nicholas finch wrote:

Sorry, one thing I forgot to add is w hy the batteries in series get screw ed w hen one battery reaches before the others, it is because current in series f low s the same through all of the

batteries in series.

If you w ere just charging a single battery from empty, and you applied the charger and measured the voltage it w ould be low , and the current f low ing into the battery w ould be high. As

the voltage in the battery increases ( as it is approaching full ) the current automatically slow s dow n, and w hen the battery voltage = the charger voltage, there should be zero current

f low . With batteries in series, other batteries that are not full can force current f low through the allready full batteries, w hich heats them up, and this is w hat causes the problem.

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On September 30, 2012 at 8:44am

Ramhorn wrote:

For my iPhone, w hat is a good partial discharge percentage before charging?

Second, is it possible to condition li-ion batteries. Say, fully discharging the battery the f irst time you get your iPhone4, than after that apply the method of never fully discharge before

charging. Will this condition the battery, as it is new , to be able take more stress afterw ards?

On October 1, 2012 at 10:01pm

MARK WILSON wrote:

Thank-you for your insight Mr. Finch. I w as not aw are of the need of a BMS w hen I started my project. I have all w inter to ponder my options for my Ebike pack here in New England. I

had not mentioned earlier that my charger is only 4 amps or 8 amps if I use my 2 li-ion chargers to charge tw o 36 volt packs separately. The pack w ill be w ell over 100 amphours, so

charging fully from drained w ill take a very long time. It w ill likely be charging any time it is not being discharged, so this w ill help. A rainy day w ill provide an extra 24 hours of charge for

my bike. I am w ondering if the damage( or at least the safety risk) to a cell in series w ill be minimized by using such a “trickle” charge. I suppose that if I w ant to eliminate the risk of

causing any one cell from being too stressed, then the current from the charger should not exceed the C rating of any one cell as that cell is acting as a charger for the next cell in series

that hasn’t yet reached the full 4 volts that I am asking each cell to accept. I w ill likely try to get by w ith using only one 4 amp charger and adjusting the pots w ithin w hile measuring voltage

w ith my multimeter to change the charger to 72 volts.

I surmise that not maximizing charge to 4.2 per cell, but rather only 4 volts and only draining to 20 percent w ill help negate the balancing issue. I currently plan to only utilize the middle 60%

of the pack’s potential. My riding range w ill suffer, but that is w hy I am building such a ridiculously large pack. Range @ ~25mph should approach or exceed 50 miles. Maybe I should

have spent 3 times as much money for a battery from the conversion kit vendor, but then I w ould only have 20amphours and know very little about lithium ion science. Tinkering is good

fun.

On October 13, 2012 at 4:36pm

Marsman wrote:

I’ve been playing around w ith some Makita 18v 3Ah Li-ion battery packs. The charger is a fast charger (approx 20minutes) it really pumps current into the packs w ith short on/off cycles in

excess of 10amps. the battery gets quite w arm w hich is not good for Li-ion. As I’m not a “tradie” I use my tools occaisionally and don’t feel such brutal charging is necessary so I’ve

investiagted alternative chargers including one that w ill w ork from my car battery (Makita sells one for over $150 !!! no thanks!). I found the universal laptop chargers are nearly on the

mark, they have selectable voltages and have a 20v setting (one I got w as exactly 20.1V and w as able to deliver > 5amps). This equates to about 4.02V per cell, very safe even though

you only charge to about 80% capacity. It still charges the battery in about 1 hour w ith current tapering dow n from about 5 amps to zero). I don’t intend leaving the batteries connected

but at this voltage I presume it w ould be ok. Interested in experts comments on w hat I am doing? at about $15 Australian on Ebay it represents a 90% saving on Makita chargers. The

battery packs have all sorts of protection in them so I’m not really w orried but reading this forum, balanced cell charging might be a concern over time? added advantage is that if the

packs have been over discharged the makita charger see’s them as faulty and w on’t charge but the Ebay charger doesn’t care (see numerous forums on this topic)

On October 24, 2012 at 11:49am

Paolo wrote:

Hi,

f irst of all, thank you for this usefull post!

I’m w orking on a Li-Ion battery pack 6-cell, 10.8V 5600mAh, coming from my macbook.

The battery is pretty old and has discharged due to inactivity below 9.0 V, causing the protection circuit to sw itch over. In this state, its charger (magsafe 60W) doesn’t recognize it and it

is helpless for me.

For this i’ve decided to try charging it manually. I have a pow er supply 12V 1.08 A that seems to be suitable, also if it has less pow er, i said to myself “it’ll employ just 3 times more”: the

strange is that there is an intermittent current absorption, normally 150 mA w ith peak at 1.5 A. Voltage seems to grow according to your graph in stage 1.

Do you think can be acceptable? Or is not good to charge w ith less pow er?

On October 29, 2012 at 5:11am

marsman wrote:

they are actually connected 3 series connected sets of 2 in parallel.

you really need to manually charge them carefully, not exceeding about 12.2 volts. most plug pack adapters that say 12v dc are not regulated and w ill put out over 15v w ith little load, they

w ill over charge the li ion pack and maybe blow it up if left too long. if you keep measuring the voltage and stop at 12.2 volts you should be ok i think. that should make them look ok to the

proper charger but 9v should not be too low you may have a faulty pack

On October 30, 2012 at 4:11am

paolo @marsman wrote:

right marsman,

in fact they w ent in overvoltage, i’ve used a charge holder for car battery w ith a resistive load to have the right voltage drop (near 2.5 V) and w hen the current fell dow n, the drop had

diminished so at the end my barrery w as at nearly 13.6 !!! I used a little load to discharge them and now they keep back to 12 V ....

How can i test if they are faulty ? They seems fine for a little load (directly connected), but the mac still refuse to boot ... anyw ay i’ve ordered a new pack, keeping this one for play ...

thnak you

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On October 30, 2012 at 6:17am

idan sl wrote:

For my iPhone, w hat is better:

1. To charge it all night (8 hours) ?

or

2. To charge it tw ice a day half a charge?

THX

On November 2, 2012 at 12:22am

Elliot Craig wrote:

Why are li-ion individual cells only 3.2v? The reason I ask is for DIY EV applications the cost of the BMS is very expensive, and if the voltage w as doubled w ith the same amps, the cost

of BMS w ould be much less, half the cells to monitor.

On November 2, 2012 at 12:33am

Elliot Craig wrote:

Why are lifepo4 individual cells only nominal voltage 3.2v? The reason I ask is for DIY EV applications the cost of the BMS is very expensive, if the voltage w as double for example w ith

the same amps, the cost of BMS w ould be much less as only half the cells required.

Many thanks

On November 10, 2012 at 5:39am

Hans wrote:

When you say “Discontinue using charger and/or battery if the battery gets excessively w arm”, w hat is the temperature range you should discontinue charging? I have a new battery in

my phone and during charging the battery temperature reaches 43’C.

On November 26, 2012 at 7:26pm

Michael wrote:

thank you very much AWESOME

On January 8, 2013 at 6:05pm

Herieza wrote:

Thanks so much for the full mastery and comprehensive article…

much more convincing by your research.

On January 10, 2013 at 5:52pm

Brian Burns wrote:

I have heard some people state that, in terms of pow er draw n by the charger vs capacity gained in the charged cell, lithium batteries charge most eff iciently in Stage 1 and that in Stage 2

the charger uses much more energy to deliver the last bit of capacity to the cell. Is this true?

On January 15, 2013 at 1:07am

MARTIN NTLHE wrote:

Exellent piece of information, but I have a question. I w ould like to know if there is a minimum charge of voltage for li-Ion batteries?

On January 20, 2013 at 10:01am

Jack wrote:

I have a smartphone w ith 2100mAh capacity, I have quite a number different USB chargers, all w ith the same voltage (5.0v) but different amperage output from 0.5A to 1.5A. Except my

iPad charger (it is rated at 5.1V, 2.1 A output).

I w onder charging my phone w ith the iPad charger w ith damage my battery in long term?

I read you reply to nolan above mentioned that w e should never charge the battery larger than 1C? I am a bit lost in how to calculate C. It doesn’t come into the formula or Watt = VI

Thanks!

On January 20, 2013 at 4:10pm

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Vince wrote:

Hi Jack,

The 5V and 5.1V things aren’t really chargers. They are just USB type pow er sources used for pow ering the charger. I mean, you can’t really hook a battery itself up to any of them.

You plug a phone or other device into the 5(5.1)V pow er source, and the phone itself contains the charger w hich charges the battery at 4.2V.

The value of C refers to how much current w ould it take to completely discharge a fully charged battery in one hour. So C for your smartphone battery is 2100mA, or 2.1A.

Coincidentally, your ipad “charger” is rated for 2.1A. But remember that it is not really a charger. If it w ere rated for 100A, it w ould still be okay. That means that it w ould be capable of

putting out up to 100A of current, but it is the actual charger inside the device that determines how much of that “up to 100A” it w ould draw , and how much it w ould send to the battery.

For example, a typical household socket is rated for 15A, but most things you p[lug into it w on’t draw anyw here near that amount of current.

Also, the 2.1A * 5.1V pow er supply is = 10.71 Watts, but the 2.1A “C” value for the battery is at 4.2V, w hich is 8.82W. (2.1A * 4.2V)

On January 26, 2013 at 7:03am

Vince wrote:

@Martin, re: minimum charge voltage

Yes, and maybe no. A smartphone, for example, may have a minimum voltage at w hich the phone w ill shut dow n and w on’t come back “on”. And then the cell itself, or battery, should

also have a tiny circuit board, w hich, as far as I understand, is supposed to prevent it from being draw n dow n below a different (and low er) minimum voltage, and also to prevent it from

being overcharged. And then there is another point, even low er, below w hich the cell is truly dead and w ill not accept a charge. So each minimum exists to prevent it from reaching the

next minimum.

On January 26, 2013 at 7:23am

Vince wrote:

@Martin, more info:

I just found this board, a Protection Circuit Module:

http://w w w .all-battery.com/protectioncircuitmodulepcbfor37vli-polymerbattery85alimit-pcb1s.aspx

It’s specs show a maximum of 4.25V and a minimum of 2.5V.

On January 26, 2013 at 6:00pm

Damon Lee wrote:

I had a new Goki, 3.7v Lithium-ion battery for my cell phone. I charged the battery w ith the original charger. When I plugged it to the pow er source and the red light w as on the charger

and I unplugged it w hen I saw the light changed to green. Please tell me. Is the battery fully charged? Or should I charged the battery for a certain hours? Please help. Damon Lee ( the old

timer)

On January 26, 2013 at 7:59pm

Vince wrote:

@Damon Lee, Not really sure. I guess it may depend on your charger, and w hat makes it decide to turn green. Right now I’m eating a pizza, and soon I’ll decide I’m full. But after I w ait a

w hile and let things settle, I’ll have room again for a little more.

Batteries charging are a lot like me eating pizza.

Fast chargers w ill feed the battery a lot of charge quicker than it can settle. They w ill reach that 4.2V mark in a hurry, but then after you take the battery off the charger, it w ill go dow n

sooner than if you slow charged it.

Ultimately, if that’s your only charger, then you don’t have a choice. I assume that once the light turns green, it quits sending out a charge. So leaving it on the charger w on’t accomplish

anything if that’s true, nor w ill it hurt anything.

I think the best w ay to f ind out if it is really fully charged is to take it off, leave it off for a few hours, and then put it back on and see if it takes more charge (red instead of green).

On January 28, 2013 at 4:38am

Dave wrote:

Very informative article, although I have a question:

Having charged my LiOn battery, and on the multimeter it show s up as 4.2V, my camera still show s “battery empty” w hen I sw itch it on, and w ould then sw itch off automatically.

Any idea w hy?

On January 28, 2013 at 8:51am

Vince wrote:

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@Dave, assuming that there’s nothing w rong w ith the camera itself, this normally indicates that the battery is at the end of its useful life for the camera. Cameras are high-drain devices,

meaning that they require more current than other devices. The battery may have 4.2V, but can no longer maintain that voltage output at the required amperage. As soon as a normal load

is applied to the battery, it’s voltage drops quickly to a low or unusable point. But once the load is removed, the battery voltage may measure high again.

It’s also possible that something inside the battery has gone w rong. In any case, it’s time for a new battery.

On January 28, 2013 at 10:32am

Alan Levi wrote:

According to http://en.w ikipedia.org/w iki/Lithium-ion_battery, charge eff iciency of Lithium-Ion batteries is typically in the 80% to 90% range. This is very different from the claim that

“Charge eff iciency is 97 to 99 percent” in this article. Can somebody reconcile this difference?

Alan

On January 28, 2013 at 10:47am

Vince wrote:

I’m no expert, but I read that to mean charge eff iciency is 97 to 99 percent during stage one, w hen the battery is starting out from near empty and is able to accept nearly all of the energy

it’s receiving. This is w hen it stays coolest. Tow ard the end of the entire charging cycle, even though there is still a slight charging current, the accumulated charge in the cell reaches a

maximum and w on’t increase. Therefore, at that point, there is 0% eff iciency, all current supplied is being w asted elsew here.

Eff iciency is how much of the energy consumed is being used for the desired purpose. The rest is w asted as heat. Electric space heaters, for example, are all 100% eff icient because it

is their intended purpose to give off heat, so none of the energy they consume is “w asted”.

On January 28, 2013 at 11:07am

Alan Levi wrote:

Vince, understood. It w ould be nice to see charge eff iciency as a function of time added to Figure 3 (or f igure 1). I w onder w hat typical threshold values are for various techniques of

detecting the cross-over from stage-1 to stage-2. ... and w hat the techniques are. If a battery is not used for a signif icant amount of time (e.g. overnight for a car battery), the charging

logic w ill need to periodically recharge the battery if there’s enough loss. If this re-top-off is required frequently, then the cross-over period can become quite signif icant in overall

eff iciency (energy-in / energy-stored) of charging.

On January 30, 2013 at 11:06am

Phil Fouracre wrote:

Found this site, really interesting. Can anyone advise me as to how lithium ion batteries on electric bikes actually w ork. I have one w ith eight spring loaded pins for the output connection

to the bike and am w ondering w hat do w hat, does this mean that it has four separate cells, or w ould some terminals be associated w ith monitoring or other sensing controls. Am

interested so that I can measure and monitor output and performance

On January 30, 2013 at 11:25am

Ben wrote:

Hey,

I got a question concerning my Lumia 920:

When I use my Lumia, it starts to shut dow n at about 4% of battery charge. When I then perform a soft reset and start the phone again, I suddendly have more than 20% battery, w ithout

charging it. My question is, if this is for safety reasons (so that the battery w ill never be discharged completly - but 20% seems pretty much), or if this is just a softw are bug w here the

correct battery charge is not read out correctly?

Because I really w ould like to use the 20% too, but if this w ill demage my battery, I w ould prefere to charge it.

I hope someone can answ er my question.

On January 31, 2013 at 12:44am

Vince wrote:

Ben, no I w ouldn’t w orry about it damaging your battery. There’s no w ay to read how much charge is left. The voltage is the closest w e have, and that’s not real accurate. When you

use the battery, the voltage w ill drop. The faster you use it, the faster the voltage drops. But then if you let it sit, the voltage w ill increase. The faster you had been using it, the more you

can expect it to increase. This is because you can draw more current than the battery can provide for long. Think of it like a bottle of ketchup. When it gets close to empty, you really

have to be patient to get the last few drops out.

On February 4, 2013 at 2:25pm

Bob wrote:

• I’ve read that LIo batteries have 2 stages. 1st staged charges faster than 2nd. I’ve been monitoring my HTC Inspire phone w ith a couple of battery w idgets that w ill graph the charge and

discharge rates over time. I’ve been noticing that if the battery is less than 50% and charging, the charge speeds up extremely fast to 100% after it gets to to approx 72%. The charge

graph is not linear but slightly curved until it reaches 70-75% then the battery go to full charge immediately. I’m doing a test again and currently the battery is at 67%, Battery health is

GOOD, temp is 84.2 F, Battery voltage is 4.201V. I’m using the mfg w all charger that came w ith the HTC. Is this normal for the battery to top off like that so fast? Also w hen the battery is

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higher than 80% the charge rate seems to be more linear up to 100%. Thanks for any thoughts.

On February 6, 2013 at 8:26am

Vince wrote:

@Bob, no, those results do not seem normal to me. But remember that the amount of charge stored in a cell cannot be measured, so your phone is just guestimating those percentages.

4.2V is normally considered 100% full, meaning that you don’t w ant to go higher than that. For it to be 4.2V and still show only 67% charged means you phone is making bad guesses.

Remember that if charged too quickly, it could reach 4.2V w ithout being full. If you let it sit for a w hile, that voltage w ill fall and it w ill be able to take more charge. If you charge it slow ly

enough, it w ill be more fully saturated at every voltage along the w ay, and w ill hold that voltage once off the charger.

Myself, I use extended batteries that my phone w asn’t designed for. I’ve learned to pretty much ignore the percentage that my phone reports. I w atch the actual voltage instead, again

understanding that it does not accurately represent charge, and w ill f luctuate a lot. But it’s a better indicator than the guestimated percentage.

On February 11, 2013 at 11:50am

Tony wrote:

I have a Paritrek-S portable nebulizer my w ife occasionally uses for asthma. The “pow er pack” is expensive and tw o have failed in past ~3 years. I opened one of them and it contains a

charging circuit board w ith components and tw o Li-io size 18650 cells. What fails is only the cells (18 months and 12 months) . The unit is not used very often and w e try to maintain cells

charged by “boost” charging every 1 - 3 months or so. It is foolish to spend $120 again w hen all I need to do is remove (already done) the tabbed batteries and replace them for about $24

or so. Qustion is…I cannot identify if batteries are 1500mAh, 2200mAh, or 2600mAh. They drive a small motor/pump. I am thinking of getting the 2200mAh for about $24 for tw o. Other than

duration for driving the small pump, do you think it w ill matter on capacity as charger circuit is in tact? In other w ords, w ill impact just be charging time if mAh rating is incorrect? (Cannot

determine the LG originals rating)

On February 11, 2013 at 4:37pm

Vince wrote:

Tony, I w ouldn’t think changing the capacity should affect anything except runtime and charging time. In fact, as the cells deteriorate, their capacity goes dow n anyw ay. The rated

capacity is the “new ” capacity.

On February 27, 2013 at 8:13pm

Jimi Diga wrote:

Hi Vince,

Would you know the voltage tolerance of the built-in chargers of mobile phones?

My HTC’s plug says 5v—1000maH but I’d like to use a battery pack w ith a rating of 5.3v—1000maH. Will the .3 voltage difference damage my phone’s battery or lessen its life cycles?

Thank you very much in advance!

On February 28, 2013 at 2:08am

Vince wrote:

Hi Jimi,

No, sorry, I w ouldn’t. My phone is a Droid, w hich is the only source of my limited experience. But your question is puzzling, or maybe I don’t understand.

As far as I know , all lithium cells have a rating of 3.7v nominal (meaning average voltage), w ith a w orking range of about 4.2 to 3.2 volts.

A “battery pack” w ould imply multiple individual cells. If w ired in parallel, they w ould maintain the same voltage, 4.2 - 3.2. If w ired in series, tw o cells w ould produce a battery of 8.4 - 6.4

volts, rated I guess at 7.4. (That’s 3.7 x 2.) So I don’t understand w here you can get 5.3v from. ???

Remember that the 5v “plug” is not the charger. It is the source that provides pow er to the charger in the phone. Are you sure the plug says 1000maH, and not just 1000 mA? mah (milli

amp hours) w ould be a measure of capacity, w hich w ould apply to a battery (or “cell”). ma (milli amps) on the other hand w ould be a measure of current, w hich w ould apply to a pow er

cord, for example.

1000 mah seems like a very small battery for a modern phone. My batteries are 3500mah. (At 3.7v nominal.) The chargers usually get their pow er from a cord rated at 5V, 1000 ma

current.

On March 2, 2013 at 7:05pm

Berno wrote:

how to boosted fairly new sleeping li-ion ultrafire.

thank you

On March 4, 2013 at 2:50am

John wrote:

I’m building a small battery operated radio pow ered by a 18650 3000mAh (supposedly).

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I’m trying to incorporate a built-in charger using a purpose IC - MCP73831 or MCP73837.

I’ve hit the problem of leaving the radio sw itched on w hile on charge because, as your article says, the charger may never “see” a current below the termination value and may continue

to charge (at Stage 2).

I’m w ondering if devices w hich do allow themselves to be pow ered w hile charging (phones, ipads etc) simply rely on using only enough current to allow the charger current to drop

below the threshold or if they use some other method of not “confusing” the charger.

Thanks.

On March 5, 2013 at 4:25am

Chris G wrote:

LiFe 3.3v LiIon 3.6v LiPo 3.7v, there is a difference betw een lithium ion and lithium polymer batteries. This article suggests there isn’t w hich is w hy I mention that there is a difference.

On March 5, 2013 at 5:11am

John wrote:

I found a useful Application Note by Microchip about simultaneously charging a Lithium battery w hile draw ing current from it:

http://w w 1.microchip.com/dow nloads/en/AppNotes/01149c.pdf

On March 5, 2013 at 10:53pm

Ricky Aspartame wrote:

So w ould a 5.3v rated after market plug hurt a mobile phone w ith a packaged 5v rated plug?

On March 6, 2013 at 10:55am

House Mouse wrote:

What can be used to measure the drop in current and sw itch off the supply of pow er to a 5v pow er supply.

On March 6, 2013 at 11:18am

Josh wrote:

Vince,

From the information presented here and elsew here, I have divulged that charging at a low er C value is desirable for the long-term health of a li-ion battery. In my case, I have a cell phone

w ith a non-removable battery, so I am limited to using the built-in charger (& thus cannot slow -charge using an external charger like you mentioned in your comment on Feb 23 2012).

Given that my phone came w ith a 5.1V / 850mA ac adapter, w ould I be doing my phone a service if I instead used an adapter rated for 5 V / 550mA? My main concern lies in using an

adapter that w as not bundled w ith my phone (though both adapters in question are Motorola branded).

For w hat it’s w orth, I realize I can connect to a PC USB port to charge at ~500mA, but I cannot do this w hile the phone is turned off (my phone pow ers on w hen plugged into a PC USB

port)—and this article clearly advises that “A portable device should be turned off w hile charging.”

Thanks.

On March 6, 2013 at 12:49pm

Vince wrote:

Hi Josh, yes, the adapter you’re talking about w ould w ork f ine, and w ould charge it more slow ly. And yes, it’s f ind to have modern phones on w hile charging, so using your PC w ould be

perfect. On my phone, w hen I plug it in to the PC, the phone gives me some options such as using it as a Mass storage device, or charge only. I alw ays choose “charge only” unless I

w ant to transfer data from the phone to the pc.

If you use the phone w hile it’s charging, it w ill charge more slow ly, w hich is actually a good thing! If I’m on a long road trip, using GPS and streaming Pandora, I have to keep it plugged in

or it w ill run out of juice.

On March 12, 2013 at 6:34pm

Adam wrote:

I need help! I bought 2 rechargeable li-ion 9v batteries. Brand name is Maximal Pow er. I need 2 of them hooked up in the 9v clips to give me about 16 volts for led lighting. They w ill go for

about 30 minutes super bright, then one of the batteries cuts off, dimming the lights to almost nothing. Why is it doing this??? I got 2 replacements…. Still not w orking no matter w hich of

the 4 I use…..

On March 14, 2013 at 11:26pm

SRV wrote:

Hi

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I am planning to use 2 Li-ion batteries 4.2V and1.5Ah in parallel.

The charge current of individual battery is 750mA.

I am designing a charger circuit for the same configuration.

The charger circuit should be designed for a 1,5A, is my understanding correct?

Can i use a linear charger?

I am w ondering how w ill the charge current be divided among the batteries.

Any information on charging the batteries in parallel combintion w ill be helpful?

On March 20, 2013 at 5:49am

ken wrote:

my galaxy s3 come w ith 2100mah standard 3.8v & limit 4.35v

now my issue is that during my idle mode 4.0x~4.1x volt & during charging mode it hit up 4.2x volt.. my temp hit up easily around 39~44ºc

is that meaning my battery lifespan r declined? 9mths old battery only.. how can i undervolt it? really need ur guys assistance. thanks!

On March 20, 2013 at 6:49am

Vince wrote:

Hi Ken, yes, I’m no expert, but I think you’re correct in that fully charging your battery like this w ill reduce it’s lifespan in order to give you maximum run time. If that’s not w hat you w ant,

then you have some options.

First, try charging it from a computer’s USB port instead of a w all charger. A computer’s USB port is supposed to limit current to 500ma at 5v. This w ill give you a slow er, cooler, better

charge.

Second, w hile also using the f irst suggestion, look for an app that alerts you w hen the phone voltage reaches a certain point, like 4.1v for example, and unplug it at that point.

Third, instead of using the above suggestions, don’t use your phone to charge the battery. This is the option I use. I bought a charger on ebay (it w as very cheap) and it charges very

slow ly. I like this option because I no longer need to plug my phone in. Very convenient. Each morning, I just sw ap the battery w ith the one that had been sitting on the slow charger all

day the previous day and night.

On March 20, 2013 at 7:58am

ken wrote:

@vince thanks for the feedback. open any apps,surf ing,video call, & etc less than 5 min it w ill hit up 38~39ºc

now idle staying at 28ºc/4.06v

if charging w ith USB i get around 4.1x volt

w all charger >> 4.205v depend on temp. if higher the temp, the higher the volt than can reached 4.274v (max)

ambient temp around 29~32ºc w hile playing/surf ing it w ill hit up 39~42ºc.

i get restart once due to overheat that reached 45ºc if no mistake.

conclusion, is time for new battery!

On March 20, 2013 at 8:51am

Vince wrote:

Ken, also consider that if you are using the phone to charge the battery, how do you know if the source of the heat is the battery or the phone? Phones are computers, and after a w hile

there w ill be a lot of things installed and running that you aren’t aw are of. I see computers that are slow and hot and loud, the fan trying to keep cool the overw orked cpu. Sometimes a

reformat and reload w orks w onders.

Could also just need a new battery like you said.

On March 20, 2013 at 8:58am

ken wrote:

i just guessing cos previously i remember my voltage are f luctuating around 3.8~3.9v

maybe is spyw are cos recently i installed lucky patcher. i removed all recently apps doesn’t solve the issue & hard reset my phone it seems slightly better but more or less the same. i

think of hardw are issue. if lappy fan loud try kill rundll32.exe & avoid open the game explorer at start menu. i bought laptop nearly 3 yrs never reformat. hehe

On March 20, 2013 at 9:55am

Tony wrote:

on Feb 11 I posted:I have a Paritrek-S portable nebulizer my w ife occasionally uses for asthma. The “pow er pack” is expensive and tw o have failed in past ~3 years. I opened one of them

and it contains a charging circuit board w ith components and tw o Li-io size 18650 cells. What fails is only the cells (18 months and 12 months) . The unit is not used very often and w e try

to maintain cells charged by “boost” charging every 1 - 3 months or so. It is foolish to spend $120 again w hen all I need to do is remove (already done) the tabbed batteries and replace

them for about $24 or so. Qustion is…I cannot identify if batteries are 1500mAh, 2200mAh, or 2600mAh. They drive a small motor/pump. I am thinking of getting the 2200mAh for about $24

for tw o. Other than duration for driving the small pump, do you think it w ill matter on capacity as charger circuit is in tact? In other w ords, w ill impact just be charging time if mAh rating is

incorrect? (Cannot determine the LG originals rating)>

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Since then, I ordered and installed tw o 2600mAH cells, as mfr. w ould not give me “time of day”...they w ork as good as new !! No overheating, charge time about the same as originals .. I

took a best guess at the LG cells that died and loks like all is great. “Vince” had replied: “ony, I w ouldn’t think changing the capacity should affect anything except runtime and charging

time. In fact, as the cells deteriorate, their capacity goes dow n anyw ay. The rated capacity is the “new ” capacity. ” looks like Vince is correct!!

On March 20, 2013 at 11:19am

Vince wrote:

Cool! Thanks for the feedback!

On March 26, 2013 at 12:11pm

Sam Emrys wrote:

@Tony No need to w orry it w ill w ork f ine just the w ay it is supposed to be…

The capacity has no great impact w ith the charger circuit unless the charger current is too much high for the new batteries w hich is possible only if the new ly installed battery’s capacity

is too much low er then the rated capacity for the charger. since the charging current in Li-ion battery isn’t much critical factor as compared to Lead acid battery there is no major effect at

all except the charging time. Batteries do have internal resistance so the current w on’t vary much unless the charging voltage is increased.

let say the internal resistance of battery is 3ohm, voltage suplied is 4.2V

now the theoretical max current draw n by battery w ill be (ignoring the charge already stored in the battery) = 4.2/3 = 1.4A w hich w ill increase only if the voltage increased or if the

resistance decreases ( Resistance w ill decrease upon charging but as the charge increases it w ill compensate and w ill reduce the current)

On March 26, 2013 at 12:13pm

Sam Emrys wrote:

@Tony No need to w orry it w ill w ork f ine just the w ay it is supposed to be…

The capacity has no great impact w ith the charger circuit unless the charger current is too much high for the new batteries w hich is possible only if the new ly installed battery’s capacity

is too much low er then the rated capacity for the charger. since the charging current in Li-ion battery isn’t much critical factor as compared to Lead acid battery there is no major effect at

all except the charging time. Batteries do have internal resistance so the current w on’t vary much unless the charging voltage is increased.

let say the internal resistance of battery is 3ohm, voltage suplied is 4.2V

now the theoretical max current draw n by battery w ill be (ignoring the charge already stored in the battery) = 4.2/3 = 1.4A w hich w ill increase only if the voltage increased or if the

resistance decreases ( Resistance w ill decrease upon charging but as the charge increases it w ill compensate and w ill reduce the current)

On March 26, 2013 at 12:15pm

Sam Emrys wrote:

@Tony No need to w orry it w ill w ork f ine just the w ay it is supposed to be…

On March 26, 2013 at 12:21pm

Tony wrote:

Installed w eeks ago…w orks great! Installing same batteries (2nd new set) in the other “pow er pack” that originally failed. Saved myself almost $100 on each unit as mfr. w ill not repair and

just sells new pow er packs. Batteries are the only thing that fail and both w ith tabs are easily replaced once unit is opened. Mfr. w ould not reply or give me “time of day” w hen I

requested by phone and email the battery specs. But, had to be one of tw o or three battery capacities.

On March 27, 2013 at 7:41am

Chris wrote:

Am I damaging my batteries?

I see battery charging voltage and operational voltage in the battery specif ication. Battery charging voltage is 3.65V, Operational voltage is 3.3V. I am charging below this voltage at

3.44V and I see the cell voltages rise quickly initially then slow ly up to 3.45 then suddenly to 3.65V w hen charging shuts off. Is this healthy for an LiFePO4 battery? I notice temperature

rises of 2 degree Celsius in the pack. The pack is made up of 16 cells rated at 48V.

Am I damaging the cells by letting them go up to 3.65V?

On March 27, 2013 at 7:58am

Vince wrote:

Batteries, even rechargeable ones, are disposable items. Asking if you’re damaging one is like asking if you’re damaging your pencil by using it to w rite a letter. Yes, but that’s w hat it’s

meant for.

Current can only f low from a higher voltage source into low er voltage. So in order to charge a battery, you must charge it w ith a voltage higher than w hat it is already at. If you’re

charging your battery at 3.44v, then the battery w ill never be charged above that. If the battery eventually reaches a voltage of 3.65, than at least at some point, it w as being charged

w ith at least 3.65v.

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If you keep everything w ithin the manufacturer’s specif ications, it should perform as intended. The intention is not to make them last the longest, but to get the most use from them.

On March 28, 2013 at 2:03am

JP wrote:

Hi, i have a Li-ion Battery, 3.7V, 700MAh , and i’d like to charge it.

How can i do w ithout the original charger ?

Thank you

On March 28, 2013 at 5:56am

Sam Emrys wrote:

@JP

use voltage regulator LM317, see the datasheet, configure it to 4.2V

On March 29, 2013 at 9:26am

Vince wrote:

Hi JP, Any lithium ion charger should w ork f ine. You can either buy one or make one.

I’ve bought a few really cheap ones, and they all suck really bad except for this one:

http://w w w .lenmar.com/w eb/ProductDetails.aspx?ProductID=PPUCLIP

If you w ant to build your ow n, w ithout starting from scratch, here’s probably the easiest kit:

http://w w w .adafruit.com/products/1304

Have fun!

Vince

PS, you could also probably f ind a stand alone charger built specif ically for your particular cell on ebay.

On May 1, 2013 at 6:03am

RJ wrote:

Hello,

My name is Robert Jones and I am contacting you in reference to Lithium Ion batteries. I am seeking some safety information for these types of batteries. I read your article and

understand w here these batteries is subject to overheating and can lead to f ire and explosion, but I didn’t see anything to prove my case of supplying an eye-w ash show er for personnel

if they are exposed to the active materials inside of these units. Also, are there any EPA regulations for these type industrial Lithium Ion batteries? The internal makeup is made up of

oxide and lithiated carbon and I’m w ondering if there are any supporting documents that states that an eye-w ash show er is required be provided in a Lithium Battery Supply house?

Make a long story short, w e are designing a PV system for grid and w e are using/charging industrial Lithium Ion batteries to supply to pow er to the grid and w e couldn’t f ind any

supporting documents that states it’s required to provide an eye w ash for such a system is case of contamination. Your insight w ill be greatly appreciated.

RJ

On May 1, 2013 at 8:07am

Gabe wrote:

I just built a battery pack to replace one that w as w orn out. The old pack had six cheap Chinese 3000mAh 18650’S. I bought six Orbtronic 3400mAh batteries for the new pack but the old

charger w ill not charge them. The batteries need to charge simultaneously because they are tab-w elded together. Any suggestions?

On May 3, 2013 at 9:00am

Randy Constan wrote:

Well I have a project I’d like to try to actually market involving a transmitter /controller, w hich seems to run really w ell for days w ith just a little single 200maH lipo cell, as it only draw s a

couple of mA. The project also has a USB connector for its mcu, from w hich 4.5 volts is available from a pin (there’s a diode in there, hence the missing 1/2V). Well since I’m incorporating

a LiPO, I have to consider how it w ill be recharged, and I’m really trying to keep costs dow n, so I tried an experiment. I took the 4.5V source, added another diode (dow n to 4.0V now ) in

series w ith a 10 ohm resistor, and tried charging the battery from this arrangement. This amounts to about 80-100mA (1/2C) of charge current for maybe 1/2 minute w hen the battery is

dow n to 3V, w hich t quickly drops to a few tens of mA after a few minutes. OK, this is a really slow w ay to charge the thing, but after about 3-4hours the battery is up to almost 4V, the

current is dow n to a couple of mA, and its ready to pow er the circuit for a couple more days. Its self limiting because w ith a 4V source, the current MUST drop to zero long before

saturation.

But here’s my question. I realize that w ith just a few more parts I could use a specialized IC , but my simple diode/resistor combination is cheap and simple. Is there any reason I shouldn’t

do it this w ay? I seriously doubt this w ould ever pose a safety risk and from the above article, I gather that at w orst I’ll seldom be fully charging the cell. But, then again this could mean

more charge cycles, and if the run time from charging this w ay is acceptable, w hat is the dow nside?

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On May 3, 2013 at 9:42am

Vince wrote:

@Randy,

I’m no expert, but that sounds perfectly reasonable to me!

Vince

On May 10, 2013 at 11:23pm

Ronnie wrote:

I regularly use Li-ion batteries, 650mah and 1300mah. I have tw o chargers one is 100mah the other 420mah, the former takes up to 6 hours to charge a 650mah battery. Can anyone tel

me w hich is the safest?

Ron

On May 10, 2013 at 11:58pm

Vince wrote:

It doesn’t make any sense that a charger w ould be rated in mah. That w ould be like saying a garden hose is rated for seven gallons. What does that mean?

If all other characteristics are the same, a charger that charges slow er is gentler on a battery than one that charges faster.

On May 11, 2013 at 9:52am

Randy Constan wrote:

I agree w ith Vince, but the w ay products are marketed these days it doesn’t surprise me one bit that even technical specif ications w ould have incorrect terms. That said, from the

explanations on this page I’d say that “1C” is both a typical and safe charge rate, but also that charging at low er rates could give you more charge cycles. “1C” for 650 mAh or 1300 mAh

battery w ould be 650 mA and 1300 mA (not mAh) respectively. So in my opinion, unless you need it charged in a harry the low er charger rate is easier on the batteries. But 100mA for

either of these batteries seems excessively low .

You also might consider getting yourself an inexpensive digital multimeter, if only to f ind out w hat current each of these combinations actually are.

On May 29, 2013 at 9:21am

paola wrote:

Hello,

I have a cell phone battery and 1100mAh 3.7 v, I am using it for an application that is not the phone, my question is, if it is necessary to put an electronic circuit to charge the battery or you

only have to let the internal circuit battery voltage w ill charge it w ith 5V, how advisable is to do this? ..

thanks for your reply

On May 29, 2013 at 12:32pm

Ronnie wrote:

Of course it makes sense that a charger delivers different mAh. Similarly a 15mm pipe w ill deliver less w ater than 22mm hence pipe sizing formula w hen installing heating systems. I just

w ant to know w hich is safest!

On May 29, 2013 at 6:03pm

Mario wrote:

Paola, some Li-ion cells have built in over charge protection but I w ould never rely on that. To be safe, you need to use a charging circuit that w ould never exceed 4.2V applied to the

battery.

Ronnie, you have not specif ied how your chargers w ork, how ever assuming the chargers are designed for Li-ion ie they can handle the initial surge charging current and don’t apply

more than 4.2v per Li-ion battery then they are both safe. Use the higher current rated charger. One w ord of w arning- if your battery is faulty (they often short out w hen faulty) it’s like

putting a short circuit across your charger. Good chargers w ill shut dow n or current limit but cheap ones may overload and heat up to the point of meltdow n. Check your cells are not

shorted before charging ie they measure at least 2.5 volts

On May 30, 2013 at 4:02pm

Leon King wrote:

I w ant to buy a Lithium Iron battery for my motorcycle. Can I use my old trickle charger w hich I used on the previous lead-acid battery?

On June 4, 2013 at 10:26pm

Mario wrote:

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Leon, definitely no. Read the info at the top of this page

On June 14, 2013 at 3:02am

vagos wrote:

at w hich states do you suggest charging an iphone battery ?

plugingi it in at 20% and remove it at 80% is that good ??

On June 14, 2013 at 6:05am

Randy Constan wrote:

@Paula: An electronic circuit is definitely the best w ay, because unlike NiCad cells w hich are not harmed by a constant trickle charge, a simple trickle charge on LiPO cells w ill eventually

charge them to a voltage that degrades their longevity. There are good IC based LIPO cell chargers like the MAX 1555 if you don’t mind laying out a PC board to hold such a tiny part. It is

also possible to make a simple self limiting charge circuit w ith a few ordinary size parts if you don’t mind a slow charge. For example, a 5V source such as available from a USB pow er

cable can be routed through a couple of diodes and a 10 ohm resistor, as I described a few posts back. It w ill provide a 100mA charge that gradually tapers off to near zero as the

battery gets to 4 volts. But even that circuit w ill eventually exceed the undesirable 4.2 volt point if left charging indefinitely. That’s f ine if you don’t mind hanging a voltmeter across the

battery and w atching it charge, to disconnect at the ideal time. But for unattended charging its not such a good idea. After a lot of experimentation I’ve concluded that a dedicated chip or

other precision circuit really is the best w ay to go.

On June 14, 2013 at 8:08am

Vince wrote:

If the current tapers off to zero as the battery reaches 4v, then how w ould it ever get to 4.2?

On June 14, 2013 at 2:16pm

Randy Constan wrote:

Well Vince, I observed it tapper off to zero, but looking closer and for a longer period of time it didn’t. It seems I didn’t take into account that forw ard voltage drop across an ordinary silicon

diode can drop low er than I ever thought it could, as the current through it drops to NEAR zero. It took a long time for it to happen, but after several days, 5V through 2 Si diodes and a 10R

resistor, the battery voltage actually made it up to 4.3. I doubt I’d ever leave the circuit charging for days like that, especially off a USB port cable w hich is hard to miss. So for a personal

project this might be f ine. But in my case I’m w orking on a project I’d like to consider marketing someday, so I decided to splurge on the MAX1555 and the couple of capacitors it needs to

w ork right. And the max1555 does seem to w ork very w ell, by the w ay!

On June 14, 2013 at 3:29pm

Vince wrote:

Ah yes, I misunderstood. I thought you w ere trickle charging it at 4V. Now it makes sense. Thanks.

On June 18, 2013 at 11:18am

Luken wrote:

Hi, I just got a new 1600 mah 3.7V Li-ion battery for my phone (instead of the original 1200mah 3.7V).

Charging from USB port, it says the battery is immediately full w hen its empty.

Using a 5.2V 1200 ma charger nothing happens at all, but this charger w orks on the old 1200mah 3.7V battery.

Any reason for this, other than that the new battery simply doesnt w ork?

On June 18, 2013 at 12:45pm

Randy Constan wrote:

Luken: I don’t w ant to make assumptions here… w as the original; 1200mah also a Li-ion cell, or some other chemistry? If it w as different, chargers are very specif ically designed to w atch

voltage levels w hile charging, so a charger meant for one chemistry w ill be confused by another. The other question doesn’t make sense. Unless you left something out, I’m not sure how

a 5.2v charger w ould apply to any Li-ion battery.

Also, I’ve seen several cases of LiPo batteries coming already fully charged. How do you know its’ “empty”? Does the phone w ork at all? Are all its metal contact points in exactly the

same place?

On June 19, 2013 at 5:49am

Luken wrote:

Hi,

The original w as also Li-ion, yes.

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Phone is completely dead w ith the new battery inserted. When “charging” the battery from the mains, phone remains dead. Charger light also periodically f lashes from red (charging) to

green (connected to mains, but not charging).

When charging from the USB port, phone charges for about a minute, then gives battery full reading. On disconnecting, the phone quickly loses life and dies.

Im confused by the voltage reading on the charger I received as w ell. Perhaps its meant to be 4.2V? Its a 3rd party charger. Seems to charge at a much faster rate, esepecially compared

to the USB.

But in any event, bearing in mind that the charger w orks on the older low capacity battery, but does nothing w hatsoever to the new w hat w ould your conclusion be from that?

On June 19, 2013 at 8:43pm

Vince wrote:

@Luken, tw o things:

First, this thing you call a charger, does the battery plug into it? Or does it plug into your phone? If the battery plugs into it, and it is putting out 5.2V, then it probably killed your battery.

But on the other hand, if it plugs into your phone, then it is not a charger. It’s just a pow er source for your phone, and your phone itself is using its ow n built-in charger to charge your

battery.

Second, w hile I don’t know if this is exactly your situation, the symptoms you describe sound consistent w ith a dead battery. The phone, w ith it’s ow n internal charger, is probably very

confused. It thinks the battery is dead because it can’t supply enough pow er to make the phone function. But it also thinks the battery is fully charged because it can’t accept any more

pow er. That is, if the phone’s charger is putting 4.2V to the battery, but the battery is draw ing 0A of current, then it must be as full as it can get. It’s conceivable that the connectors on

the outside of the battery aren’t even connected to the cell itself. (A battery actually contains a tiny circuit board for protection.)

On June 20, 2013 at 1:58am

Raton wrote:

if the battery is of 2000 mAh then w hat should be the charger current rating? if the rating is 2000 mAh then w ill it cause any problem ?

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On June 20, 2013 at 8:16am

Vince wrote:

@Raton, battery capacity is measured in mAh, but current is just amps or milliamps, not milliamp-hours. If a 2000 mAh battery is charged at a constant current of 2000 mA (2A), then it

w ould theoretically go from empty to full in one hour. In practice, it w ill take longer because as the capacity starts to get full, the current w ill taper off tow ards zero.

But charging that fast is usually considered to be too fast. I’d aim for something in the 200ma for a slow charge to 1000ma for a fast charge. Slow er is alw ays better for the battery.

On June 20, 2013 at 1:43pm

Raton wrote:

w ill it destroy the battery ?? if charger is 1000 ma and battery is 1500mah then w ill there be any prob ??

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On June 21, 2013 at 4:08am

Luken wrote:

You’re right its a pow er source for the phone I w as referring to.

Looks like its a dud. Thanks for your help guys.

On June 21, 2013 at 5:14pm

Vince wrote:

@Raton, batteries are consumable devices, intended to be eventually destroyed by using them. Charging them more slow ly w ill destroy them more slow ly.

On June 25, 2013 at 5:00am

Goutam Reddy wrote:

There are lithium ion cells that come w ith protection circuitry built in (e.g. Ultrafire 880mAH RCR123A ). The protection circuit claims over-discharge, over-charge, and short-circuit.

What w ould be bad about using a dumb 4.2VDC (800mA) charger to charge a single, protected cell, instead of a smart charger w ith intelligent charge termination?

If I read the article correctly, the things to w orry about are:

1) overcharging a pack (need to shunt current betw een cells to even out the pack charge), but this is a single cell.

2) over-voltage on a cell can cause plating, but I’m not going above 4.2VDC.

3) mini-cycles if left to charge at 4.2VDC and then internally discharging and then charging up again- but I believe this is a property of smart-chargers being left on, not dumb w all-w arts

just holding the voltage to 4.2VDC constantly?

4) over-current: the DC adapter is limited to 800mA, so the max w e can charge at is .9C anyw ay, w hich is w ithin the 0.5-1C range.

Am I missing something else here? Thank You

On June 25, 2013 at 5:28am

Goutam Reddy wrote:

Yes, I am missing something:

The 4.2VDC w all w art w ill be delivering a lot of current to the battery, if for some reason the battery dips below 4.2V, because there is no resistor in the circuity limiting the amount of

current. So, w hile .9C is f ine in the begging, it’s not good for extended periods… and w ill lead to plating?... and kill the life of the battery.

On June 25, 2013 at 1:34pm

Vince wrote:

@Goutam, good questions, and I w ould also like to know the same if anyone know s. I’ve been operating under the assumption that a dumb charger is probably f ine. The battery itself w ill

be limiting the current. As it’s voltage approaches the voltage of the charger, the current w ill drop, and eventually become zero w hen they are equal.

On June 29, 2013 at 9:46pm

Joe Noel wrote:

w hat kind of charger is best for my Li-Ion 1100mAh 3.7v?

On July 9, 2013 at 4:04am

Jim wrote:

Is there an absolute minimum charging current?

I have a small solar panel that provides 12v at 0.2A. I w ant to charge a 14.4Ahr li-ion battery pack. The AC charger that comes w ith provides 12v at 1.2A so I w ould be providing 1/6 the

current w ith the solar panel, w ould this hurt anything?

On July 16, 2013 at 9:54am

Vince wrote:

Hi Jim, No, there is no minimum. The slow er the current, the longer it w ill take to charge. Your panel w ill just take six times longer to charge the pack, but no problem.

How ever, I am in a similar situation, and there is a different problem. It seems that solar panels can be overloaded. As the current being draw n by the charging device approaches the

maximum the panel can provide, the voltage drops. This is a particular problem on cloudy days, or in the morning/evening w hen your solar isn’t receiving perfect sunlight. As the voltage

drops, the w hole system crashes for a second before recovering. But the recovery may only last a fraction of a second, w hich can result in 80% dow ntime.

Here is an excellent article on this problem: http://learn.adafruit.com/usb-dc-and-solar-lipoly-charger/design-notes

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This is from a DIY kit for using solar to charge Li-Ion. I have bought and built tw o of them, and can attest to the fact that they do w ork.

On August 4, 2013 at 2:36pm

Subutay wrote:

What is the max.w orking temparature for li-ion batteries.

My battery group contain 4 series 18650 cell group in 10 shunt battery and still temperature raising rapidly to 50 c and termal termostat is cut of the current in midle of the w orking

progress.I am not sure the 50 c is correct w orking temperature.

On August 6, 2013 at 5:39am

Ping wrote:

0V Lithium polymer battery chargable. When Lithium polymer connected to product. It keeps in standby mode nearly 1 year. The Lithium polymer battery (Without protect circuit) from 3.7V

drops below 0.08V. The battery can rechargable ( w ithout protect circuit ) but it prevent by protect circuit. What is problem if charge 0V Lithium polymer battery?

On August 6, 2013 at 10:37am

Jez Xuereb wrote:

I have a LI Ion battery for mobilty scooter. It contains 2 cells and is rated 25.34V 218Wh.

Its charger needs replacing (it has an output of 29.4V 5A).

Can I use an electric bike charger - 25.90V 2A output ?

I do not mind if it takes longer to charge the battery.

On August 6, 2013 at 11:17am

Jez Xue wrote:

I need a backup charger for my mobility scooter battery.

My main charger has output of 29V 5A.

Can I use a bike charger w ith output of 24/29V 2A?

I think the battery has 2 cells and is rated 25.3V 218Wh.

Does the number of cells matter as to type of charger?

On August 7, 2013 at 8:17am

Vince wrote:

Batteries are usually rated at the nominal voltage, w hich is their normal, or average operating voltage. For example, a typical lithium ion cell is 3.7v nominal. It is full at 4.2v and pretty

empty at 3.2v. 3.7v is its half w ay point.

So in your case, if you use a 25.9v charger to charge a 25.3v battery, you w ill only get it up to about half charge. I don’t think it should hurt anything. You just w on’t be able to get a full

charge out of it, w hich is probably around 29v.

On August 11, 2013 at 3:43am

Selvol wrote:

This site has been the greatest non biases source of info around for years.

Thank you

On August 11, 2013 at 5:34am

Jex Xue wrote:

@Vince

Thank you.

On September 3, 2013 at 5:00pm

Damian wrote:

Hi,

Is it possible to trickle charge a Li-ion battery using a portable solar charger?

and w ould this damage the battery?

Thanks

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On September 3, 2013 at 5:15pm

Damian wrote:

Hi,

can Li-ion batteries be trickle charged via a portable solar charger?

and can this cause any damage to the battery?

Thanks

On September 5, 2013 at 6:17am

Vince wrote:

As long as the charging voltage is correct (usually 4.2V) it w ouldn’t matter w hether the source of that voltage is from a phone’s charger, solar panel, or hamster in a w heel. I have a

series of contraptions for charging my batteries. I have a solar panel that outputs 0-15.3 volts depending on solar conditions, w hich in turn pow ers a 12v-5v USB adapter, w hich sends

5v to anything designed to accept 5v, such as a phone or a standalone charger, w hich f inally supplies 4.2v to the battery itself.

Things to consider w hen using a solar panel: If you overload the panel, trying to draw more current than it can supply, possibly due to cloud cover for example, the solar panel output

voltage may crash to zero. This shouldn’t cause any harm, except that it w on’t charge the battery, and may even drain it.

Also, w hile the solar panel must be in direct sunlight, take care to ensure that the charger itself, and the battery, are shaded and have cool. Simply covering them w ith a dark panel may

actually cause greater heat.

On September 14, 2013 at 12:21am

Enrique Batikoff wrote:

Excellent, very interesting paper covers a lot of subjects regarding design Lio charging methods to be employed

On September 14, 2013 at 12:29pm

Bill wrote:

If I put a 1.2V rechargeable battery in series in a 1.2V constant on circuit w ith a load:

1. Will my total voltage be 2.4V ?

2. Would this in effect be a trickle charger for the battery ?

3. Might the battery discharge and, if so, should I use a diode betw een the battery and the incoming 1.2V ?

4. Would it be best to use a Li-Ion, a NiCad, or a NiMH battery ?

This is a great site !!!

Thanks.

On September 19, 2013 at 12:14am

Nestoras wrote:

If i have my mobile phone plug on the charger overnight this w ill cause an overcharge?

On September 19, 2013 at 6:29am

Vince wrote:

Charge moves from higher voltage to low er voltage. The only w ay to charge a battery beyond 4.2v is to charge it w ith more than 4.2v.

On September 19, 2013 at 6:32am

Nestoras wrote:

Dear Vince,

Thank you.

On September 29, 2013 at 9:18am

Milap wrote:

I have a problem w ith my li ion battery of my mobile.

It charges to 82% in about 2 hours 30 minutes and suddenly w ithin 5 minutes it show s 100%.

Same w ith discharging…It discharges to 30% normally and w ithin 5 minutes it show s 15%.

What can be the problem? i keep my phone sw itched off during charging..and charge only after battery reaches 0%.

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I have also replaced the battery but the problem remains.Kindly guide me.

On September 29, 2013 at 11:20am

Vince wrote:

The good new s is that you do not have a problem w ith your battery. It’s just that your phone does not accurately know the percentage of your charge, so it guesses, usually based on

usage.

Most phones usually charge the battery at 4.2v. They can frequently (maybe once each second) w atch how much current is going into the battery, and thereby “count up” how many

mah of charge it is up to. And the same process w hen discharging, counting dow n from full how much you’ve used. You cannot accurately “measure” the charge left in you battery by

looking at it’s voltage, because there is not a linear relationship.

As your battery ages, it is not able to store as much, so the phone may only charge w hat it thinks should be 82% of the battery’s capacity, but w hen the battery w ill suddenly not accept

any more charge, then it realizes that it’s at 100%, as full as it’s going to get.

You could try a battery calibration procedure, w hich actually does nothing to the battery, but should help teach the phone w hat the upper and low er limits of the battery are. How ever,

w hat you’ve described yourself already doing is essentially the same thing.

Ultimately, it sounds like a phone problem, not a battery problem. I’d ignore it, personally, and just remember that 82% means almost full, and 30% means almost dead.

On September 30, 2013 at 1:59am

Milap wrote:

But my phone is new .

Just 1 month old and I am facing the problem since the f irst day.

Is there a defect in phone?

On September 30, 2013 at 10:15am

Vince wrote:

It may be a defect, or it may be a design problem, or it may be normal.

I’d ask the person you bought it from, or the manufacturer, if all phones of that model behave in that manner. If yes, then that’s the w ay that phone w as designed. If no, then it is

defective and they should f ix it.

It almost sounds like it might be basing the reading on voltage, w hich is w hat I have my phone do by using an app called Battery Monitor. By default, it show s 100% at 4.2V, 0% at 3.2V,

and is linear in betw een. On a fresh charge up to 4.2V it w ill show 100%, but drop almost instantly as soon as it is unplugged. From there it drops very quickly at f irst, then spends most

of it’s time around the 60%-40% range, w here it changes very little, then once below 30% it w ill drop very quickly again. I myself just learn to understand w hat these numbers really

mean, and don’t take them at their face value.

On October 3, 2013 at 11:42pm

NUR MOHAMMAD wrote:

about know ledge

On October 7, 2013 at 3:37pm

Blake Cooper wrote:

In the paragraph that begins w ith, “Some portable devices sit in a charge cradle in the on position…” you say that the battery is being continuously discharged to 4.20 volts per cell;

perhaps you meant 4.05 V instead of 4.20 V?

On another note, thank you very much for a great article; it is an important reference source for me.

On October 15, 2013 at 2:05am

Luciana Gama wrote:

Wow , this w as the best article regarding Li-ion batteries I could f ind!

Congrats man!

So the old habit of charging the battery for the f irst time for a full day is long dead hahahaha

i remember this w as recommended 10 years ago to extend battery life.

Well, I guess modern times are more practical.

Great, thank you for the information.

I just bought the new Galaxy note 3 and i w ill not let it charge for 9 hours… thanks!

On October 17, 2013 at 1:27pm

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Luken wrote:

“Hi, I just got a new 1600 mah 3.7V Li-ion battery for my phone (instead of the original 1200mah 3.7V).

Charging from USB port, it says the battery is immediately full w hen its empty.

Using a 5.2V 1200 ma charger nothing happens at all, but this charger w orks on the old 1200mah 3.7V battery.

Any reason for this, other than that the new battery simply doesnt w ork?”

#########

Hi I left this email a few months ago. Your response suggested it w as the battery at fault. But I’ve got the provider to send out a new battery, and that didn’t w ork either. They have a good

rating, and are unlikely to sent me 1 nonw orking battery, let alone 2, w hich w ere both brand new and untouched.

So 3 batteries-2 new er 1600mah batteries that dont w ork at all, and one old 1200mah battery that doesn’t last a day, w hich I’ve been using since.

Any suggestions/possible faults other than the battery?

On October 17, 2013 at 5:14pm

Vince wrote:

Assuming that the battery is good, then it is either empty, full, or somew here in the middle. To f ind out, leave the battery off the charger for a couple hours, then use a multimeter to

measure the voltage betw een the + and - terminals. Anything over 4v is pretty full, and anything under 3.4v is pretty low . 3.7v is nominal, average, half w ay.

If the battery is bad, it could read full, and yet not be able to supply enough current to pow er your phone for very long. But w e’re assuming that the battery is good.

If a good battery is full, but w on’t run the phone, then the phone is bad. If a good battery is empty but w on’t charge, then the charger is bad. Remember, the charger is either built into the

phone, or you may be using an external charger, w hich is a cradle the battery sits in. The pow er cord for the phone is not a charger, only a pow er cord.

On October 18, 2013 at 10:59am

Teacher Tom wrote:

Great info…

I cannot f ind any info on how to use Li-ion w ith solar cells in a solar car. Our High School is building an electric three w heeler w ith solar cells to augment the pow er of our 11.2V, 60Ahr x

7 packs. Can w e charge and run at the same time or do w e need to manage our use sw itching betw een both pow er sources charging only w hen w e are stopped?

On October 19, 2013 at 8:56am

Vince wrote:

I don’t know anything about solar cars, but I’d say that any additional pow er source you provide to the car w ill be that much less that the battery has to provide. I assume your solar

source can’t provide enough to keep up w ith the demands of the car w hile it’s in use, or you w ouldn’t need a battery. Wouldn’t that be nice!

So w ithout using any real numbers, let’s say a load needs 20 w atts, and a charger can only provide 10 w atts, then for every hour you use the device, it w ould take tw ice as long to

recharge it. But if you’re applying the source and the battery together, then the device can get 10 of it’s required w atts from the solar, and now the battery only has to provide 10 more,

and so you can use the device for tw ice as long before the battery is empty, at w hich time the device w ould try to get all its pow er from the solar source, w hich can’t provide enough,

and you’re dead in the w ater until you recharge.

On October 19, 2013 at 9:01am

Vince wrote:

I should also mention, and probably you already know , that I didn’t take into account the different voltages involved, and so you w ould need some circuitry to make things like they need to

be. For example, a typical laptop computer pow er cord supplies 19v. But the battery may only be an 11v battery. So obviously the pow er management thingy in the computer has to

make sure the proper voltage goes to the proper destination.

On October 27, 2013 at 4:54pm

Ian wrote:

By laptop battery (lithium ion) does not charge beyond 93% w hich is ok w ith me but w hen it discharges to 26% pow er goes as if it had reached 0. Why is this, can anything be done to

correct it?

On October 27, 2013 at 5:28pm

Vince wrote:

As you use batteries, they lose some of their capacity. Your laptop isn’t aw are of the battery’s diminished capacity.

Some laptops allow you a calibrate the laptop for the battery, basically by going through a full charge and discharge cycle, w hile the laptop monitors the charging and discharging process

to learn w hat the battery’s capacity is. This calibration function is usually found in the BIOS, if it exists. Many laptops don’t have any means for recalibration.

Alternately, you can just learn and remember for yourself that 93% means full and 26% means empty. Also you may be able to reconfigure the pow er options through the Control Panel.

For example, you might tell it to display an alarm at 30%, and then go to sleep mode.

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Lastly, you can buy a new battery on ebay, usually for under $20.

On October 27, 2013 at 6:20pm

angelica wrote:

What’s the difference betw een a protected and unprotected battery? If I’m making various serie/parallel conection w hat’s best?

Also If i decide to use a PCB battery, it’s best is a buy unprotected batteries and use PCB board or it’s best to buy cells w ith the PCB include??

On October 28, 2013 at 8:51am

Vince wrote:

From the w ebsite batteryjunction.com, “Li-Ion and Li-Poly battery packs should alw ays be used w ith a protection circuit to prevent the cell from over charging or over dis-charging.

Choosing the correct circuit and applying it appropriately is vital to the longevity your batteries and your ow n safety.”

All of the batteries I’ve bought have come w ith PCBs (Protection Circuit Boards). Even if you’re making your ow n battery of batteries, I’d recommend using individual PCBs on the individual

batteries. Whether you w ant to buy w ith the PCB or add your ow n probably depends on your level of expertise.

On November 4, 2013 at 7:34am

Kevin wrote:

Hey Vince

Thanks for the useful info. I just have one question: I know you said its better to turn off the device w hen charging to prevent parasitic load. But let’s say I’m at home and w ant to w atch

netf lix on my phone, or w ork on it for a few hours, and I’m close to a charger. Is it better to keep my phone connected to prevent battery drain, or is it better to just use the battery and

charge later?

On November 4, 2013 at 7:35am

Kevin wrote:

Hey Vince

Thanks for the useful info. I just have one question: I know you said its better to turn off the device w hen charging to prevent parasitic load. But let’s say I’m at home and w ant to w atch

netf lix on my phone, or w ork on it for a few hours, and I’m close to a charger. Is it better to keep my phone connected to prevent battery drain, or is it better to just use the battery and

charge later?

On November 4, 2013 at 8:31am

Vince wrote:

A reminder to all: I am not in any w ay related w ith this w ebsite, the original article, or the author thereof. I’m just a normal reader like the rest of you. Any advice or information in the

original article didn’t come from me.

@Kevin, I’ve thought about this myself. I go through a lot of batteries, because I use them and abuse them. I normally prefer the convenience of not being plugged in. How ever, in

response to your question about w hat’s better for the battery, I think maybe it’s best to have it plugged in w hile you’re using it the heaviest.

What’s absolutely best for the battery? According to w hat I’ve read, charge it up to about half w ay, maybe 3.7-3.8 volts, remove the battery, sit it on a shelf, and don’t use it. Maybe once

a year, check it and charge it back up a little if needed. This w ill probably make it last the most number of years, because you’re not using it.

That’s not practical in the real w orld. We buy them to use them. So w hat’s the next best thing? Don’t use them any more than you have to. So if the pow er being draw n out of the

battery is the same as w hat w ould be going in to it w hen charging, then they cancel each other out, and essentially you’re not using the battery, and your phone is basically running

directly off of w all pow er.

I think probably the best thing in this scenario is to put it on the slow est charger you can f ind, such as a computer’s USB port w hich is limited to 500 mA (0.5A).

A perfect example is w hen I’m on the road, running the GPS w ith the screen on continuously, w hile streaming internet radio in the background. I’ve noticed that I can drive all day long and

never get a full charge, even though it’s plugged in. So in this case, I’m using zero charging cycles.

If this seems contradictory to the advice about parasitic load, let me add this: Any load, parasitic or otherw ise, w ill increase the time needed to achieve full charge. But once it is fully

charged, a smart charger w ill stop charging all together until the voltage drops dow n to a predetermined “sw itch back on” level, maybe 4.0v for example. If the phone is on and you’re not

using it, this w ill result in unnecessary charge/discharge cycles. So if you don’t need to use it w hile it’s charging, overnight for example, then yes, it’s best to turn it off.

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