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By NS Wickramasinghe BSc(E & E Eng)Hons
Battery
What is a Battery
collection of one or more electrochemical cells in which stored
chemical energy is converted into electrical energy
Classification of Batteries
Batteries
Other
Secondary
Primary
PhysicalEnergy
Chemical
Carbon-Zinc dry cellLithium
Mercury OxideSilver Oxide
Fuel Cell
Solar cellThermal
Nuclear Energy
Lead Acid (Flooded/Sealed)Nickel Cadmium
Lithium Secondary
Lead acid batteries architecturesDeep-cycle
Designed for maximum energy storage capacity and high cycle count (long life), and are rated in Amp/Hours. This is achieved by installing thick lead plates with limited surface area.
Typical applications are boats, Uninterruptible Power Supplies (UPS)
Engine StartingStarter batteries are made for maximum power output, usually rated in CCA (Cold-Cranking amps). The battery manufacturer obtains this by adding multiple “lead plates” to obtain larger surface area for maximum conductivity.
Typical applications are vehicles & motorcycles
Lead-Acid Battery Construction
Lead-acid batteries are commonly made of five basic components
A resilient plastic container
Positive and negative internal plates made of lead
Plate separators made of porous synthetic material
Electrolyte - 35% sulfuric acid and 65% water
Battery Terminals
Types of Lead-Acid BatteriesLead-Acid Batteries come in several
different configurations
Flooded Lead-acid – Available in Deep cycle or Engine starting as sealed or open variety
Sealed Lead-acid - The liquid electrolyte is gelled into moistened lead plate-separators, which allow the case
to be sealed. Safety valves allow venting during charge, discharge and atmospheric pressure changes.
Absorbed Glass Mat Batteries (AGM) - sealed lead-acid that uses absorbed glass mats between the plates. It is sealed, maintenance-free and the plates are rigidly mounted to withstand extensive shock and vibration
Capacity of a BatteryThe definition of Capacity is usually
given in Amp-hours (Ah) or Cold cranking amps (CCA), cranking amps
(CA), and Reserve Capacity (RC)
(Ah) is specifies the amount of current (measured in Amperes) it can provide over a 20 Hours period
(CCA) is a measurement of the number of amps a battery can deliver at 0 ° F for 30 seconds and not drop below 7.2 volts
(CA) is measured at 32 degrees F. This rating is also called marine cranking amps (MCA)
(RC) is a very important rating. This is the number of minutes a fully charged battery at 80 ° F will discharge 25 amps until the battery drops below 10.5 volts
Inside of a Lead Acid Battery
Creating Voltage
Charging a Lead-Acid Battery
Parameters for Recharging
Charging Current - All batteries have a “maximum current” at which they can be safely charged
Charging Voltage - Applying a voltage across its positive & negative terminals that is higher than the voltage it already has across them
Charging Time - The charge time of a sealed lead-acid battery is 12-16 hours (up to 36 hours for larger capacity batteries)
Electrochemistry principle of Lead Acid batteryDischarge Chemistry
Negative plate reaction: Pb(s) + HSO4-(aq) → PbSO4(s) + H+(aq)
+ 2e-
Positive plate reaction: PbO2(s) + HSO4-(aq) + 3H+(aq) + 2e- →
PbSO4(s) + 2H2O(l)
overall reaction:Pb(s) + PbO2(s) + 2H+(aq) + 2HSO4
-(aq) → 2PbSO4(s) + 2H2O(l)
Electrochemistry principle of Lead Acid battery
Charging Chemistry
Negative plate reaction: PbSO4(s) + H+(aq) + 2e- → Pb(s) + HSO4
-(aq)
Positive plate reaction: PbSO4(s) + 2H2O(l) → PbO2(s) + HSO4-
(aq) + 3H+(aq) + 2e-
Overall reaction:2PbSO4(s) + 2H2O(l) → Pb(s) + PbO2(s) + 2H+(aq) + 2HSO4
-(aq)
Battery Testing
The most accurate method is measurement of specific gravity and battery voltage
Load testing is yet another way of testing a battery
Battery health
Typical Battery Problems
Low charge Low Capacity
Mismatched Batteries
Typical Battery Problems
Conversion Efficiency
This denotes how well it converts an electrical charge into chemical
energy and back again. The higher this factor, the less energy is converted
into heat and the faster a battery can be charged without overheating. The
lower the internal resistance of a battery, the better its conversion efficiency.
Sulfation
Sulfation of lead-acid batteries starts when the electrolyte’s specific gravity falls below 1.225. It results in a salt-like substance forming on the battery plate surface and it can harden on the battery plates if left long enough, reducing and eventually blocking chemical reaction between the lead plate and the electrolyte. Equalization is the solution for this problem.
Typical Battery Problems
GassingBatteries start to gas when you attempt to charge them faster than they can absorb the energy. The excess energy is turned into heat, which then causes the electrolyte to boil and evaporate. is the suitable method for reduce this is good ventilated area.
Self-DischargeThe self-discharge rate is a measure of how much batteries discharge on their own. The self-discharge rate is governed by the construction of the battery and the properties of the components used inside the cell (alloy of the lead, sulfuric concentrations of the electrolyte, etc.).
Temperature Effects for Battery Operation
The optimum operating temperature for the lead-acid battery is 25°C (77°F).
As a guideline, every 8°C (15°F) rise in temperature will cut the battery life in half.
A VRLA, which would last for 10 years at 25°C (77°F), will only be good for 5 years if operated at 33°C (95°F).
Theoretically the same battery would last a little more than one year at a desert temperature of 42°C (107°F)
Battery sizes
Electrochemistry principle of Ni-Cd battery
positive reactsNi(OH)2 - e + OH- -> NiOOH + H2O
Negative reactionCd(OH)2 + 2e -> Cd + 2OH-
whole reaction2Ni(OH)2 + Cd(OH)2-> 2NiOOH+ Cd+
2H2O
When dischargedNiOOH + H2O + e Cd + 2OH- + 2e ->
Ni(OH)2 + OH- Cd(OH)2 Main applications are two-way radios, biomedical equipment and power tools
Electrochemistry principle of Li-ion battery
Positive reactionLiCoO2 -> Li1-xCoO2 + xLi+ +
xe-
Negative reactionC + xLi+ + xe- -> Clix whole reactionLiCoO2 + C -> Li1-xCoO2 + CLix
Applications include notebook computers portable power tools, medical devices and cell phones.
Maintenance of Batteries
Ensure proper maintenance of engine starting batteries due to the extreme importance of getting a ship under way in any
circumstances
Attention should be paid to the electrolyte level and specific gravity for vented batteries
A boost charge shall be given if the specific gravity of the battery cells meet the conditions stipulated by manufacturer
Ensure that the battery is not being overcharged
Keep engine starting batteries clean, dry and free of seawater
Period of inactivity for the ship of a week or more, give the battery a normal charge
Maintenance of Batteries Inspected for height of electrolyte once each week
The electrolyte level shall never be allowed to fall below the top of the separators
Add pure distilled water at any time to replace that which has evaporated
Add water just before the battery is placed on charge, as the water remains on top of the electrolyte until mixed with it by charging
After adding water, replace and tighten the vent plugs
Remove all water or electrolyte spilled during watering and make sure that the tops and sides of the cells are clean and dry
Maintenance of Batteries Ensure that distilled water that is to be used for
watering batteries and mixing electrolyte does not contain impurities
Use only premixed electrolyte when replacing spilled electrolyte
Fully charged specific gravity between the limits of 1.220 and 1.210 specific gravity at 27° C (80° F)
The specific gravity of a cell that has fallen below 1.210 shall not be increased by the addition of acid untill it has been definitely ascertained by test that the low-gravity condition is not due to sulfation
The addition of acid to increase the specific gravity of a sulfated cell will aggravate the existing condition
Maintenance of Batteries The specific gravity of cells which exceed
1.220 shall be cut by the removal of an appropriate amount of electrolyte and the addition of distilled water
Sulfuric acid of a specific gravity greater than 1.350 shall not be added to a battery
Precautions for Mixing Electrolyte
Personnel handling or mixing electrolyte shall wear proper protective items
If concentrated acid or electrolyte come in contact with the skin, immediately wash the affected with freshwater
As soon as possible get the medical assistance
During electrolyte mixing the acid must be poured into the water and not the water poured into the acid
The acid must be added slowly and cautiously to the water to prevent excessive heating and splashing
The solution should be continually stirred by a glass rod while the acid is being poured into the water to prevent the heavier acid from flowing to the bottom of the vessel
Instructions for Mixing Electrolyte
To prepare electrolyte, lead or rubber vessels and stirring rods are necessary
Only pure distilled water shall be used
Every effort must be made to keep impurities from the electrolyte while mixing, since they shorten battery life
Extreme care must be taken to ensure that acid container (carboys) are absolutely airtight
The addition of even a small quantity of water to a carboy of strong sulfuric acid may cause an explosion due to the sudden evolution of heat
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