Lead acid battery charger with voltage analyzerr Mini project 2011

ABSTRACT

Now-a-days maintenance free lead acid batteries are common in vehicles, inverters, and UPS systems. If the battery is left in a poor state of charge, its useful life is shortened. It also reduces the capacity and recharge ability of the battery. For older types of batteries, a hygrometer can be used to check the specific gravity of the acid, which, in turn, indicates the charge condition of the battery. However, you cannot use a hygrometer for sealed type maintenance-free batteries. The only way to know their charge level is by checking their terminal voltage.

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Lead acid battery charger with voltage analyzerr Mini project 2011

Chapter 1

INTRODUCTION

With the lack of centralized power grids, car batteries have taken the place of oneOf the

main energy sources available in developing countries. With this in mind, ourObjective will

be to design a cheap, versatile and efficient lead acid car battery charger which will interest

and appeal to the “cost-minded” customer. Today maintenance-free lead-acidbatteries are

common in vehicles,inverters, and UPS systems. If thebattery is left in a poor state of charge,

itsuseful life is shortened. It also reduces thecapacity and rechargebility of the battery.For

older types of batteries, a hygrometercan be used to check the specific gravityof the acid,

which, in turn, indicates thecharge condition of the battery. However,you cannot use a

hygrometer for sealed-type maintenance-free batteries. The onlyway to know their charge

level is by checking their terminal voltage.

To their specific users:

Universal 12 Volt battery charger

Ability to charge a typical 12 Volt lead-acid battery

Overcharge protection

State of charge indicator

Affordable

We used these requirements as guidelines to implement our product as well asInclude

additional features that we thought are important to the functionality.

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Lead acid battery charger with voltage analyzerr Mini project 2011

Chapter 2

BLOCK DAIGRAM

Each individual module was designed and constructed separately. After successful

simulation and testing, they were put together to create the finalized version.

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3. CIRCUIT DIAGRAM

3.1 CIRCUIT MODEL

Battery Voltage level to detect are

<9.8V

>9.8V

11.5V

12.0V

12.5V

Select reference voltage in 5 V

Choose a zener diode with 5V

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Resistor,Re = 5V/1.25mA

= 4k

= 3.9k(std)

Total current through the voltage level indicator circuit is limited to 0.3mA

Total resistance in the divider network = 12.5/0.3mA

= 41k

= 38k(std)

For 12.5 voltage

V=(Vcc * R5)/(total resistance)

5V=(12.5 * R5)/(38k)

R5=15.2k

= 15k(std)

For 12 voltage

V=(Vcc * (R5+R4))/(Total Resistance)

5V=(12*(15.2+R4))/(38k)

R4=15.83-15.2

=0.63k

=680ohm(std)

For 11.5 voltage

V=(Vcc*(R5+R4+R3))/(Total Resistance)

5=(11.5*(15.83+R3))/(total Resistance)

R3=16.52-15.83

=0.691ohm

= 680ohm(std)

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For 9.8 voltage

V=(Vcc*(R5+R4+R3+R2))/(Total Resistance)

5=(9.8*(16.52+R2))/(38)

R2=19.38-16.52

=2.86k

=2.7k(std)

Resistor, R1 = Total Resistance – (R2+R3+R4+R5)

= 38 – 19.38 k

= 18.62k

= 18k

Resistor R7 to R10

= 5V/(10mA)

= 500ohm

= 470ohm(std)

Trasnsformer 12V,2A

So diode used for rectifier is IN 5408 ( 4 No’s)

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4. COMPONENTS USED

1. 230V AC Primary to 0-12V 2AMP Secondary Transformer

2. Diode IN5402

3. IC LM324

4. PZ1 Piezo Buzzer

5. LED

6. Capacitor

7. Zener Diode

8. Resistor

9. Fuse

10. Crocodile Clips

11. PCB

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Chapter 5.

COMPONENT DESCRIPTION

5.1. 230V AC Primary to 0-12V 2AMP Secondary Transformer

A transformer is an electrical device that transfers energy from one circuit to another by

magnetic coupling with no moving parts. A transformer comprises of two or more coupled

windings, or a single tapped winding and, in most cases, a magnetic core to concentrate the

flux. An alternating current in one winding creates a time-varying magnetic flux in the core,

which induces a voltage in the other windings. Transformers are used to convert between

high and low voltages, to change impedance, and to provide electrical isolation between

circuits.

If a load is connected to the secondary, an electric current will flow in the secondary

winding and electrical energy will be transferred from the primary circuit through the

transformer to the load. In an ideal transformer, the induced voltage in the secondary winding

(VS) is in proportion to the primary voltage (VP), and is given by the ratio of the number of

turns in the secondary (NS) to the number of turns in the primary (NP) as follows:

By appropriate selection of the ratio of turns, a transformer thus allows an alternating current

(AC) voltage to be "stepped up" by making NS greater than NP, or "stepped down" by making

NS less than NP. In the vast majority of transformers, the windings are coils wound around a

ferromagnetic core, air-core transformers being a notable exception.

Transformers range in size from a thumbnail-sized coupling transformer hidden inside

a stage microphone to huge units weighing hundreds of tons used to interconnect portions of

power grids. All operate with the same basic principles, although the range of designs is

wide. While new technologies have eliminated the need for transformers in some electronic

circuits, transformers are still found in nearly all electronic devices designed for household

("mains") voltage. Transformers are essential for high voltage power transmission, which

makes long distance transmission economically practical.

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5.2.Diode IN5402

A signal diode is one of many types of diodes, which are small components of electrical

circuits, manufactured from semiconductors that force electricity to flow in only one

direction. Signal diodes which are also sometimes known by their older name of the Point

Contact or Glass Diode are physically very small in size compared to their larger Power

Diode cousins and control small currents up to about 100mA. Generally, the PN-junction of a

signal diode is encapsulated in glass to protect it and they generally have a red or black band

at one end of their body to help identify which end is its Cathode terminal.

Silicon diodes are designed to pass very small currents, and have several applications

in the signal processing field. The arrow in the symbol of diode points in the direction of

conventional current flow through the diode meaning that the diode will only conduct if a

positive supply is connected to the Anode (A) terminal and a negative supply is connected to

the Cathode (K) terminal thus only allowing current to flow through it in one direction only,

acting more like a one way electrical valve, (Forward Biased Condition). However, we know

that if we connect the external energy source in the other direction the diode will block any

current flowing through it and instead will act like an open switch, in reverse biased mode.

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The characteristics of a signal point contact diode are different for both germanium and

silicon types and are given as: Germanium Signal Diodes - These have a low reverse

resistance value giving a lower forward volt drop across the junction, typically only about

0.2-0.3v, but have a higher forward resistance value because of their small junction area.

Silicon Signal Diodes - These have a very high value of reverse resistance and give a forward

volt drop of about 0.6-0.7v across the junction. They have fairly low values of forward

resistance giving them high peak values of forward current and reverse voltage. Signal

Diodes are manufactured in a wide range of voltage and current ratings. There are

bewildering arrays of static characteristics associated with the humble signal diode but the

important ones are as follows; maximum forward current, peak inverse voltage and maximum

operating temperature. The diode characteristics are shown in Figure.

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5.3.IC LM324

An operational amplifier ("op-amp") is a DC-coupled high-gain electronic voltage amplifier

with a differential input and, usually, a single-ended output. An op-amp produces an output

voltage that is typically hundreds of thousands times larger than the voltage difference

between its input terminals.

5.4.Piezo Buzzer

A buzzer or beeper is an audio signaling device, which may be mechanical,

electromechanical, or Piezoelectric. Typical uses of buzzers and beepers include alarms,

timers and confirmation of user input such as a mouse click or keystroke

5.5.LED

A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in

many devices and are increasingly used for other lighting. Introduced as a practical electronic

component in 1962, early LEDs emitted low-intensity red light, but modern versions are

available across the visible, ultraviolet and infrared wavelengths, with very high brightness.

When a light-emitting diode is forward biased (switched on), electrons are able to

recombine with electron holes within the device, releasing energy in the form of photons.

This effect is called electroluminescence and the color of the light (corresponding to the

energy of the photon) is determined by the energy gap of the semiconductor. An LED is often Dept. of EEE 11

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small in area (less than 1 mm2), and integrated optical components may be used to shape its

radiation pattern.LEDs present many advantages over incandescent light sources including

lower energy consumption, longer lifetime, improved robustness, smaller size, faster

switching, and greater durability and reliability. LEDs powerful enough for room lighting are

relatively expensive and require more precise current and heat management than compact

fluorescent lamp sources of comparable output.

5.6.Capacitor

A capacitor (formerly known as condenser) is a device for storing electric charge. The forms

of practical capacitors vary widely, but all contain at least two conductors separated by a non-

conductor. Capacitors used as parts of electrical systems, for example, consist of metal foils

separated by a layer of insulating film.

A capacitor is a passive electronic component consisting of a pair of conductors

separated by a dielectric (insulator). When there is a potential difference (voltage) across the

conductors, a static electric field develops across the dielectric, causing positive charge to

collect on one plate and negative charge on the other plate. Energy is stored in the

electrostatic field. An ideal capacitor is characterized by a single constant value, capacitance,

measured in farads. This is the ratio of the electric charge on each conductor to the potential

difference between them.

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5.7.Zener Diode

A Zener diode is a type of diode that permits current not only in the forward direction

like a normal diode, but also in the reverse direction if the voltage is larger than the

breakdown voltage known as "Zener knee voltage" or "Zener voltage". The device was

named after Clarence Zener, who discovered this electrical property.

A conventional solid-state diode will not allow significant current if it is reverse-

biased below its reverse breakdown voltage. When the reverse bias breakdown voltage is

exceeded, a conventional diode is subject to high current due to avalanche breakdown. Unless

this current is limited by circuitry, the diode will be permanently damaged due to

overheating. In case of large forward bias (current in the direction of the arrow), the diode

exhibits a voltage drop due to its junction built-in voltage and internal resistance. The amount

of the voltage drop depends on the semiconductor material and the doping concentrations.

5.8.Resistor

A resistor is a two-terminal passive electronic component which implements electrical

resistance as a circuit element. When a voltage V is applied across the terminals of a resistor,

a current I will flow through the resistor in direct proportion to that voltage. This constant of

proportionality is called conductance, G. The reciprocal of the conductance is known as the

resistance R, since, with a given voltage V, a larger value of R further "resists" the flow of

current I as given by Ohm's law:

5.9.Fuse (2.5 AMP)

A fuse is a type of sacrificial overcurrent protection device. Its essential component is a

metal wire or strip that melts when too much current flows, which interrupts the circuit in

which it is connected. Short circuit, overload or device failure is often the reason for

excessive current.

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A fuse interrupts excessive current (blows) so that further damage by overheating or fire

is prevented. Wiring regulations often define a maximum fuse current rating for particular

circuits. Overcurrent protection devices are essential in electrical systems to limit threats to

human life and property damage. Fuses are selected to allow passage of normal current and of

excessive current only for short periods

5.10 Crocodile Clips

A crocodile clip (or spring clip) is a temporary electrical connector, named for its

resemblance to a crocodile's jaws. Functioning much like a spring-loaded clothespin, the

clip's two tapered, serrated jaws are forced together by a spring to make them grip a metal

object. One of the jaws usually has either a wire permanently attached or a 4 mm banana plug

inserted into it, for connection to an electrical circuit. The clip may be partly covered by a

plastic shroud or "boot" to prevent accidental short-circuits.

5.11. PCB

Printed circuit board, or PCB, is used to mechanically support and electrically connect

electronic components using conductive pathways, tracks or signal traces etched from copper

sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring

board (PWB) or etched wiring board. A PCB populated with electronic components is a

printed circuit assembly (PCA), also known as a printed circuit board assembly (PCBA).

Printed circuit boards are used in virtually all but the simplest commercially-produced

electronic devices.

PCBs are inexpensive, and can be highly reliable. They require much more layout

effort and higher initial cost than either wire wrap or point-to-point construction, but are

much cheaper and faster for high-volume production; the production and soldering of PCBs

can be done by totally automated equipment

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Chapter 6

WORKING

When the circuit is connected to the battery and push switch S2 is pressed (withS1

open), the battery voltage is sampled by the analyzer circuit. If the supply voltage sample

applied to the non-inverting input of an op-amp exceeds the reference voltage applied to the

inverting inputs, the output of the op-amp goes high and the LED connected at its output

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Lights up.

The different levels of battery voltages are indicated by LED1 through LED4. All the LEDs

remain lit when the battery is fully charged (above 12.5V). The buzzer connected to the

output of IC1 also sounds (when S2 is pressed with S1 kept open) as long as the voltage of

battery is above9.8V. If the voltage level goes below 9.8V, the buzzer goes off;this indicates

that it’s time to replace the battery. The status of LEDs for different battery voltages is shown

in the table.

The circuit can be assembled on a general- purpose PCB or a bred board. Use

4mmwire and crocodileclips to connect the charger to the battery. A 2.5-amp fuse connected

to the output of the charger protects the analyzer circuit against accidental polarity reversal.

Chapter 7

RESULT

The circuit presented here can replenish the charge in a battery within 6-8 hours. It

also has a voltage analyzing circuit for quick checking of voltage before start of charging,

since overcharging may damage the battery. The voltage analyzer gives an audio-visual

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indication of the battery voltage level and also warns about the critical voltage level at which

the battery requires immediate charging.

The status of LEDs for different battery voltages is shown in the table.

Chapter 8

CONCLUSION

We were able to accomplish our main goal, and that is design a working prototype for a 12V

lead-acid battery.

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Lead acid battery charger with voltage analyzerr Mini project 2011

In this project we have learned more than just how to make a simple universal battery

charger and drawing upon our EE knowledge from our previous classes. We experienced our

first taste of design and major project management. Along with these specific skills, we also

improved our time management and team work skills. Throughour design project we

experience many success and failures in the process, and have had to make a lot of important

design decisions. With more time we could have taken our rough design and brought it to

usable standalone charger.

BIBILOGRAPHY

1. RV owners’ forum:

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http://www.trailerlife.com/cforum/index.cfm/fuseaction/thread/tid/683429/gotomsg/683780. cfm

2. Boaters World: www.boatersworld.com

3. Battery Stuff.com: http://www.4unique.com/battery/soneil/soneil-12v2-5a.htm

4. PCB Pro.com: http://www.pcbpro.com

5. Powerstream.com: www.powerstream.com/PV-Control.htm

6. Datasheetwww.datasheet.in

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ANNEXURE

CONTENTS

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Lead acid battery charger with voltage analyzerr Mini project 2011

Introduction 1

Block Diagram 2

Circuit Diagram 3

Components used 6

Component Description 7

Working 13

Result 14

Conclusion 15

Bibliography 16

Annexure ` 17

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