Battery Monitoring And Charging System

PROJECT REPORT

ON

Battery Monitoring and Charging System (Integrated with Inverter)

Submitted for the partial fulfilment of requirement for the

Seventh semester of Degree of Bachelor of Engineering in Electronics and

Telecommunication of Gauhati University.

Session 2011

SUBMITTED BY Yuvajit Dutta (G/08 – 154) Md. Mainuddin Ahmed (G/08 – 155) Imran Hussain (G/08 – 169) Bhaskar Jyoti Bora (G/08 – 173)

Under the guidance

of

Mrs. Sharmila Nath Asst. Prof., E.T.E.

Department of Electronics and Telecommunication Engineering

Girijananda Chowdhury Institute of Management and Technology

Azara, Hathkhowapara,

Guwahati – 781017 (Assam)

GIRIJANANDA CHOWDHURY INSTITUTE OF MANAGEMENT AND TECHNOLOGY HATHKHOWAPARA, AZARA, GUWAHATI – 781017

DEPARTMENT OF ELECTRONICS & TELECOMMUNICATION ENGINEERING

Certificate from the Head Of the Department Certified that the following students of 7th Semester BE in Electronics & Telecommunication

Engineering.

1. Mr. Yuvajit Dutta

2. Mr. Mainuddin Ahmed

3. Mr. Imran Hussain

4. Mr. Bhaskar Jyoti Bora

Have submitted Project Report on “Battery Monitoring and Charging System (Integrated with

Inverter)” in partial fulfilment for the award of the degree of Bachelor of Engineering in

Electronics & Telecommunication Engineering, GIMT, Azara, Guwahati – 781017.

Date:

Place:

(Signature)

Head of the Department

Electronics & Telecommunication Engineering

GIMT, Azara, Guwahati - 781017

GIRIJANANDA CHOWDHURY INSTITUTE OF MANAGEMENT AND TECHNOLOGY HATHKHOWAPARA, AZARA, GUWAHATI – 781017

DEPARTMENT OF ELECTRONICS & TELECOMMUNICATION ENGINEERING

CERTIFICATE This is to certify that the project report entitled “Battery Monitoring and Charging System

(Integrated with Inverter)” has been carried out and presented by

1. Mr. Yuvajit Dutta

2. Mr. Mainuddin Ahmed

3. Mr. Imran Hussain

4. Mr. Bhaskar Jyoti Bora

Students of 7th semester (BE), Department of Electronics & Telecommunication

Engineering, GIMT, under my supervision and guidance in a manner, satisfactory to

warrant its acceptance as a pre – requisite for the award of Bachelor of Engineering degree

in Electronics & Telecommunication of Gauhati University.

Date: Guide:

Place:

(Signature)

Mrs. Sharmila Nath

Assistant Professor, GIMT

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ACKNOWLEDGEMENT

We would like to express our profound gratitude to Dr. Mukulesh Barua,

Principal, GIMT, Guwahati, for giving us to carry out our project work.

We are grateful to Prof. Abhijit Nath, Head of the Department, Electronics &

Telecommunication, GIMT, Guwahati, for his cheerful encouragement and valuable

suggestions.

We wish to express our heartfelt thanks to our guide Mrs. Sharmila Nath,

Assistant Professor, ETE Dept. GIMT, Guwahati, for her valuable suggestions and

cheerful encouragement to carry out our project work.

Lastly we express our gratitude to our parents and all our friends who helped,

in one way or the other.

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ABSTRACT

With the rapid development of communication, electric power, UPS, etc. there

are more and more maintenance-free lead acid battery used in all kinds of areas. The

quality of its performance is very important to ensure the normal running of reserve

power. At the same time, there are lots of problems.

1. The service life is shorter than it should be.

2. Individual bad cell causes the battery-pack out of service.

3. It's not easy to find the sudden battery failure timely.

4. It is a high risk for discharging test.

5. It's hard to test the lead acid battery by hand and the test date is analysed

by high professional level repairer.

6. The daily check fee is very high.

7. Lack of science and effective monitoring management, it's hard to make

accurate judgments about the proper usage for lead acid battery.

8. The power-supply device can’t really do its job well as a battery

management.

Relevant data shows that most of lead acid batteries can't go through the

capacity test after they are used for about 3-4 years, while few can exceed six years.

As a matter of fact, only few people check the lead acid battery on a regular basis and

make the regular capacity test. Most find its discharging capacity can't meet the

design demand just when power is off. Some battery packs go on working even if it is

lower than 50% of the rated capacity. It implies that the user of lead acid battery

needs to monitor the performance status at any time online. It's very important for

users to monitor the performance of lead acid battery. To make full use of lead acid

batteries, we should learn more useful information to maintain them.

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LIST OF TABLES

Table No. Name of the Table Page No.

3.1 Specifications for BMS 4

1 Electrical Characteristics at VDD=5V 18

2 Maximum Ratings and Electrical

Characteristics

21

3 Pin connections for CD4047 25

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LIST OF FIGURES

Fig. No. Name of the Figure Page No.

2.1 Basic Block Diagram 2

3.1 Circuit Diagram for BMS 5

4.1 Circuit Diagram for Charging System 9

4.2 Block Diagram of Charging System 10

4.3 Voltage Monitoring Section 11

5.1 Circuit Diagram for Inverter 13

1 Pin Diagram for TLC555CP 17

2 Functional Block Diagram of TLC555CP 18

3 Pin diagram of LM3914N 19

4 2N7000 20

5 Pin Diagram of MCR100-6 21

6 Pin Diagram for BC547 22

7 Pin Diagram for BC557 24

8 Pin Diagram for CD4047 25

9 Pin Diagram for P55NF06 27

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CONTENTS

Acknowledgement iii

Abstract iv

List of Tables vi

List of Figures vii

Chapter 1 INTRODUCTION 1

Chapter 2 BLOCK DIAGRAM 2

Chapter 3 BATTERY MONITORING SYSTEM 3

Chapter 4 CHARGING SYSTEM 8

Chapter 5 INVERTER 13

Chapter 6 CONCLUSION 15

Chapter 7 FUTURE SCOPE 16

Appendix 1: Datasheet of BMS

Appendix 2: Datasheet of Charging System

Appendix 2: Datasheet of Inverter

Bibliography

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CHAPTER 1. INTRODUCTION

Modern industrial, energy generation and distribution, medical, telecom and

transportation systems depend more and more on batteries. Battery Monitors are

designed to provide information about one’s battery bank.

In our project, we have made an analog battery monitoring system to monitor

a 12v lead acid rechargeable battery. Also it is necessary to recharge the battery hence

we have developed a charger circuit to perform charging of the battery, the battery is

also used as a source of an inverter. The inverter circuit converts dc voltage to ac

voltage.

The main objective of this project is to increase the maintenance and utility of

a rechargeable battery.

The Battery Monitoring System (BMS) monitors the battery charge.

The Charging System charges up the battery

The Inverter converts the 12V dc to 220V ac supply.

In other words we can say our project is a concise version of house hold

inverter or ups system to monitor the status of the battery constantly. As soon as the

voltage goes below a certain level which we will come to know from the BMS,

charging circuit starts charging the battery, as soon as it is fully charged it will be cut

off and the BMS starts its work again.

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CHAPTER 2. BLOCK DIAGRAM

The basic block diagram shows the complete working strategy of the project.

The 12-0-12V Step-down transformer steps down the 220V ac mains supply to

12V ac supply.

This 12V ac is used by the charging system to charge up the rechargeable

battery.

The BMS monitors the battery only after the charging system is cut-off.

The Inverter performs the task of inverting 12V dc from the battery to 220V ac

output.

Fig.2.1. Basic Block Diagram

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CHAPTER 3

3.1. BATTERY MONITORING SYSTEM

The BMS is an ultralow power ten LED battery voltmeter circuit that is

optimized for monitoring charged 12V battery systems. The circuit features an

expanded meter scale that displays ten color-coded voltage steps from 10.5V to

15.0V. Power is conserved by only turning on the appropriate LED for a short but

bright flash once every 1.25 seconds. The LED display can be turned on continuously

(no blinking) by turning the Calibrate switch on, more battery power is consumed in

this mode.

The BMS also includes a battery low voltage beeper that warns when the

battery voltage drops below a pre-set voltage. The beeper can be turned on and off

with the L.V. Beep Activate switch. The BMS is protected against reverse voltage

connection and is fused for safety. The BMS circuit is designed to work in

conjunction with both the SCC3 Solar Charge Controller and the SPC3 Solar Power

Centre.

3.1.1. FEATURES

Designed for monitoring 12 Volt rechargeable batteries.

Colour-coded voltmeter for quick battery state measurement.

Useful for alternative energy, auto marine and RV power systems.

Reliable and efficient solid-state circuitry.

Built-in fuse for short circuit protection.

Protected against reverse supply connection.

Radio quiet, will not interfere with radio systems.

Simple 2 screw connector will accept a variety of wire gauges for attaching

to a 12V power system.

Controls and Indicators

Ten ultra-bright LEDs in 5 colours, visible in sunlight with 0.5V difference.

Blink / Calibrate switch for power-efficient or constant-on LEDs.

Beep switch for enabling / disabling the low voltage beeper.

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Span and Centre adjustment trimmers for voltmeter.

Low Voltage Beep threshold adjustment trimmer.

Table 3.1. Specifications for BMS

Supply voltage 12VDC (nominal)

Display voltage range 10.5V-15V in .5V steps

Absolute maximum input voltage 17VDC

Supply Current @ 12.5V (beep off) 6.25 mA average, 30mA peak.

Supply Current @ 12.5V (beep on) 7 mA average, 34mA peak.

Blink/Beep rate 1.25 seconds per flash.

Blink/Beep duty cycle 80% off, 20% on.

Beep frequency 2.6 KHz.

L.V. Beep threshold adjustment range 7.5V-13.5V.

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3.2. CIRCUIT DIAGRAM

Fig. 3.1. Circuit Diagram of BMS

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3.3. THEORY

12VDC power is supplied to the BVM circuit via a two pin screw connector; it

is routed to the rest of the circuit through fuse F1. Diode D1 protects the circuit from

the application of reverse battery polarity on the input. Capacitor C1 filters out high

frequency noise from the power input.

With the Calibrate switch off, timer IC1 produces a low duty cycle pulse on its

output, pin 3. If the Calibrate switch is turned on, the IC1 output stays on. The output

signal is sent to MOSFET Q1, which turns the negative-side power bus of the IC2

voltmeter and the beep circuit on and off.

The LM3914N voltmeter, IC2, is wired as an expanded scale voltmeter with a

nominal voltage display from 10.5 to 15.0V in .5V steps. All of the LEDs will turn off

below 10.5V and the 15.0V LED will stay on at 15.0V and above. Potentiometer VR1

adjusts the voltage span covered by IC2 and potentiometer VR2 adjusts the voltage

point where each LED turns on. Resistor R5 sets the LED current to around 20mA.

The low voltage beeper circuit is activated by turning on S2, the L.V. Beep

Activate switch. IC4 provides a steady 5V reference. IC3a is wired as a comparator

circuit with hysteresis. IC3a compares the 5V reference to the battery voltage, which

is scaled to a value near 5V by R7, VR3 and R8. When the scaled battery voltage falls

below the reference voltage, the output of IC3a goes low and turns on IC3b, a 3 kHz

square wave oscillator. IC3b drives the piezo-speaker, PZ1. On low battery voltages,

the beep sounds when the LED blinks, or constantly if the Calibrate switch is on.

Turning the L.V. Beep Activate switch always shuts off the beeper.

3.4. WORKING

We can connect the BVM input connections to the battery terminals and turn

the Calibrate switch off and turn the L.V. Beep Activate switch on. We observe the

battery voltage on the differently coloured LEDs. If the battery voltage falls below the

warning threshold, the beeper will sound in conjunction with the LED flashes. The

L.V. Beep Activate switch can be turned off to silence the beeping. For a constantly

on LED display, we turn the Calibrate switch on.

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CHAPTER 4

4.1. CHARGING SYSTEM

Before we go into the operation of the SLA Battery Charger circuit, there are a

number of points we need to cover about the care and use of Sealed Lead Acid

batteries. Firstly, these batteries must be charged, discharged and stored very

carefully. We normally think batteries can be stored for months (if not years) and they

will be available for immediate use.

This is not the case with SLA batteries. If we store a NEW, full charged SLA

battery for 6 months or more, we will find that it may be fully discharged. We may

also find that we cannot charge it even. It may be worthless. That's how delicate

SLA batteries are. They must be charged on a regular basis to prevent them

discharging to a very low voltage level. If the terminal voltage of a SLA battery is

allowed to go below 8V, a process called SULPHATION starts to cover the surface of

the plates and prevents the battery being re-charged. The internal resistance of the

battery increases and it becomes useless.

4.1.1. DEAD BATTERIES

The circuit will not turn on if the voltage of the battery you are charging is less

than 4 volts. If you have a good battery that has been totally discharged, you can

manually start the charging process by connecting the battery and pressing the button.

This will raise the voltage on each cell and the circuit will take over in the normal

way once the voltage rises more than 4 volts.

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4.2. CIRCUIT DIAGRAM:

Fig. 4.1. Circuit Diagram of Charging System

4.3. THEORY

The circuit consists of 5 building blocks. The circuit does not turn on until a

battery is connected across the terminals as shown in the diagram. A push switch has

been provided to start the circuit when a totally flat battery is fitted. This action turns

on the PNP transistor in the "Turn ON" block. The resistance between the collector-

emitter terminals decreases and the indicator LED comes on. The path to the bottom

rail of the circuit goes through a signal diode, the gate-cathode junction of the SCR

and through two 1R8 resistors in parallel. This is why the LED illuminates.

Before we go any further, the circuit works on an AC plug pack. It must be an

AC supply as we do not want any electrolytes to be present on the power rail as this

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Fig. 4.2. Block Diagram of Charging System

will allow a very high charge-current to flow and possibly damage the SCR. A DC

supply will not allow the SCR to turn off, as it turns off when the current through it

falls to zero.

The circuit is actually a half-wave rectifier. It only charges the battery on

every half cycle. The plug pack doesn't like this as it leaves residual flux in the core of

the transformer and causes it to overheat. But that's the only drawback with the

circuit. The SCR turns on during each half cycle and current flows into the battery. A

voltage is developed across

the two 1R8 resistors (in

parallel) and this voltage is fed

into the 47u electrolytic. It

charges and turns on the

BC547 transistor. The

transistor robs the SCR of gate

voltage and the SCR turns off.

The energy in the 47u feeds

into the transistor but after a

short time it cannot keep the

transistor turned on. The transistor turns off and the SCR switches on and delivers

another pulse of current to the battery. As the battery charges, its voltage increases

and this is monitored by the "Voltage Monitor" block.

The circuit is very complex and one way to look at the operation is to consider

the top rail as a fixed rail and as the battery voltage increases, the rail connected to the

negative terminal of the battery is pushed down. This lets you see how the "Turn On"

transistor is activated and how the "Voltage Monitor" components create voltage

drops across each of them. The "Voltage Monitor" components consist of a transistor

and zener diode as well as an 8k2 resistor, the 1k pot, a 1k5 resistor, a 150R resistor

and a signal diode. The signal diode is actually part of the flasher circuit and we

discuss its operation later. As the voltage across the battery increases to 13.75 volts,

each resistor in the "voltage detecting network" will have a voltage drop across it that

corresponds to the resistance of the resistor. The diode will have a constant 0.7V

across it. The voltage on the wiper of the pot will be about 3.25V and the voltage

across the zener will be 10V. This leaves 0.6V between the base and emitter of the

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Fig. 4.3. Voltage Monitoring Section

Voltage Monitor transistor. This voltage is sufficient to turn the transistor ON. When

the Voltage Monitor transistor turns ON, it robs the "Turn On" transistor of base-

emitter voltage and the circuit turns off.

The SCR has only two states: ON and OFF. During the half-cycle when it is

turned on, the battery gets a high pulse of current and the current is only limited by

the capability of the plug pack. There are no electrolytes to allow very high pulses of

current to be delivered and this is fortunate as the SCR is only a 0.8 amp device, but

will endure surges of 10amp for half a cycle. Whenever the SCR is triggered into

conduction during the half cycle of its operation, it remains in conduction until the

voltage delivered by the plug pack falls to zero. This is when the SCR turns off. When

the plug pack delivers a negative voltage to the top rail and a positive voltage to the

lowest rail, the SCR is not triggered into conduction and none of the components in

the circuit deliver current to the battery. The SCR delivers current for a few half-

cycles and then it is turned off for a few cycles. This is how the average current

delivered to the battery is controlled.

The circuit is designed to deliver about 300 - 400 mA average charge-current.

The actual value is determined by the 1R8 resistors. When the battery is fully charged,

the indicator LED begins to flash. The flashing is produced by the 2k2 resistor and

47u (connected to the voltage monitor section). When the battery is charging, the 47u

is charged via the diode connected to the BC557 transistor and through the 150R and

signal diode to the negative of the

battery.

When the battery is fully

charged, the Voltage Monitor section

turns ON and turns off the "Turn ON"

section. This removes the voltage on the

positive side of the 47u and the positive

side is brought to the negative rail via

the 2k2 resistor. This brings down the

negative side of the 47u and the 150R

resistor is allowed to drop below the negative rail due to the presence of the diode, as

the diode becomes reverse-biased. This holds the circuit in the "off" condition, as the

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voltage monitor section sees an extra voltage across it and thinks the battery it is

"over-charged". The 47u discharges and the circuit turns ON to pump a small burst of

current into the battery to keep it charged. This is called "Trickle Mode" or "Pulse

Mode."

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CHAPTER 5

5.1. INVERTER

An inverter is circuit which converts a dc power into and ac power at desired

voltage and frequency. The ac output voltage could be fixed, at fixed or variable

frequency this conversion can be achieved either by control turn on and turn off

devices as for example BJTs and MOSFETs. Inverters can be classified according to

the wave shapes of the output voltage they are: square wave inverter, quasi square

wave inverter and pulse width modulated inverters. In this project we have made a

square wave inverter which produces a square wave ac voltage of a constant

magnitude. The output voltage of this type of inverter can only be varied by

controlling the dc input voltage. Such inverter is adequate for low and medium power

applications.

5.2. CIRCUIT DIAGRAM

Fig. 5.1 Circuit Diagram for Inverter

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5.3. THEORY

Here is the circuit diagram of a simple 100 watt inverter using IC CD4047 and

MOSFET IRF540. The circuit is simple low cost and can be even assembled on a

Vero board. CD 4047 is a low power CMOS astable/monostable multivibrator IC.

Here it is wired as an astable multivibrator producing two pulse trains of 0.01s which

are 180 degree out of phase at the pins 10 and 11 of the IC. Pin 10 is connected to the

gate of Q1 and pin 11 is connected to the gate of Q2. Resistors R3 and R4 prevents

the loading of the IC by the respective MOSFETs. When pin 10 is high, Q1 conducts

and current flows through the upper half of the transformer primary which accounts

for the positive half of the output AC voltage. When pin 11 is high Q2 conducts

and current flows through the lower half of the transformer primary in opposite

direction and it accounts for the negative half of the output AC voltage.

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CHAPTER 6

CONCLUSION

We hereby conclude that, in our project the main aim was to develop “An

Analog Battery Monitoring and Charging System”. We have succeeded in making the

BMS and tested in a 12V SLA (Sealed Lead Acid) battery which works fine. Further

we have tried to add some additional circuitry to our project, so that besides

monitoring it also provides some sort of management and utilisation of the battery and

that’s why we have made a 12V battery charger and a 12V dc to 220V ac inverter.

But while testing the 12v dc to 220v ac square wave inverter circuit we found

that the output power is too low and it can only be used to light up a simple Neon

light, so now the remaining work is to increase the output power of the inverter and

assemble all the circuits (i.e. Battery Monitoring System, Charging System and The

Inverter) so that we can make a complete commercial UPS which will provide us

approximately 45W power.

Taking a look at these goals at the end it can be said that the total cost of our

project was approx. Rs. 3000/- (INR). This project is a stepping stone to a cheaper and

efficient battery monitoring system along with 12v battery charger and inverter.

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CHAPTER 7

FUTURE SCOPE

The BVM is an ultralow power ten LED battery voltmeter circuit that is

optimized for monitoring charged 12V battery systems. So it is like an analog

voltmeter which continuously measures or monitors the status of the battery and

display the result by glowing the LEDs of different colours. So the user must know

the meaning the LED colours i.e. he should know which colour represents how much

voltage drop. So if we can make the display digital, then the user interface will

definitely increases. But eventually the cost will also increase. Again, since the design

was constructed to monitor the car battery, it will be very handy if we can attach the

circuit on the car dash. So further research and planning also would be placed on the

location of the BMS with respect to where the ON/OFF switch and indicator light

would be installed on the car dash. Similarly during testing we noticed that the

inverter output power changes with component specifications. That’s why there is a

possibility of increasing the output power level of the inverter if we can devote more

time on testing the components.

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Appendix 1: Datasheets for BMS

1. TLC555CP:

Fig. 1. Pin Diagram of TLC555CP

1.1. SPECIFICATIONS

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Fig. 2. Functional Block Diagram of TLC555CP

Table 1. Electrical Characteristics at VDD=5V

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2. LM3914N:

Fig.3. Pin diagram of LM3914N

2.1. FEATURES 2.1.1. Drives LEDs, LCDs or vacuum fluorescents

2.1.2. Bar or dot display mode externally selectable by user

2.1.3. Expandable to displays of 100 steps

2.1.4. Internal voltage reference from 1.2V to 12V

2.1.5. Operates with single supply of less than 3V

2.1.6. Inputs operate down to ground

2.1.7. Output current programmable from 2 mA to 30 mA

2.1.8. No multiplex switching or interaction between outputs

2.1.9. Input withstands ±35V without damage or false outputs

2.1.10. LED driver outputs are current regulated,

open-collectors

2.1.11. Outputs can interface with TTL or CMOS logic

2.1.12. The internal 10-step divider is floating and can be

referenced to a wide range of voltages

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3. 2N7000:

Fig. 4. 2N7000

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Appendix 2: Datasheets for Charging System 1. MCR100-6:

Fig. 5 Pin Diagram of MCR100-6

Table 2. Maximum Ratings and Electrical Characteristics

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2. BC547:

Fig. 6. Pin Diagram for BC547

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3. BC557:

1. Collector 2. Base 3. Emitter

Fig. 7. Pin Diagram for BC557

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Appendix 3: Datasheets for Inverter 1. CD4047:

Fig. 8. Pin Diagram for CD4047

Table 3: Pin Connections for CD4047

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2. P55NF06:

Fig. 9. Pin Diagram for P55NF06

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BIBLIOGRAPHY

1. Electronics For You (EFY)

2. Power Electronics – M.D.Singh and K.B.Khanchandani

3. Electronics Devices and Circuit – J.B.Gupta

4. http://www.efymag.com

5. http://www.extremecircuits.net

6. http://www.electronics-project-design.com

7. http://www.datasheet4u.com