Battery Monitoring And Charging System


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Battery Monitoring And Charging System

  1. 1. PROJECT REPORT ON Battery Monitoring and Charging System (Integrated with Inverter) Submitted for the partial fulfilment of requirement for theSeventh 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)
  2. 2. GIRIJANANDA CHOWDHURY INSTITUTE OF MANAGEMENT AND TECHNOLOGY HATHKHOWAPARA, AZARA, GUWAHATI – 781017 DEPARTMENT OF ELECTRONICS & TELECOMMUNICATION ENGINEERING Certificate from the Head Of the DepartmentCertified that the following students of 7th Semester BE in Electronics & TelecommunicationEngineering. 1. Mr. Yuvajit Dutta 2. Mr. Mainuddin Ahmed 3. Mr. Imran Hussain 4. Mr. Bhaskar Jyoti BoraHave submitted Project Report on “Battery Monitoring and Charging System (Integrated withInverter)” in partial fulfilment for the award of the degree of Bachelor of Engineering inElectronics & Telecommunication Engineering, GIMT, Azara, Guwahati – 781017.Date:Place: (Signature) Head of the Department Electronics & Telecommunication Engineering GIMT, Azara, Guwahati - 781017
  3. 3. GIRIJANANDA CHOWDHURY INSTITUTE OF MANAGEMENT AND TECHNOLOGY HATHKHOWAPARA, AZARA, GUWAHATI – 781017 DEPARTMENT OF ELECTRONICS & TELECOMMUNICATION ENGINEERING CERTIFICATEThis 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 BoraStudents of 7th semester (BE), Department of Electronics & TelecommunicationEngineering, GIMT, under my supervision and guidance in a manner, satisfactory towarrant its acceptance as a pre – requisite for the award of Bachelor of Engineering degreein Electronics & Telecommunication of Gauhati University.Date: Guide:Place: (Signature) Mrs. Sharmila Nath Assistant Professor, GIMT
  4. 4. 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 valuablesuggestions. We wish to express our heartfelt thanks to our guide Mrs. Sharmila Nath,Assistant Professor, ETE Dept. GIMT, Guwahati, for her valuable suggestions andcheerful 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.E T E Dept. GIMT iii
  5. 5. ABSTRACT With the rapid development of communication, electric power, UPS, etc. thereare more and more maintenance-free lead acid battery used in all kinds of areas. Thequality of its performance is very important to ensure the normal running of reservepower. 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. Its not easy to find the sudden battery failure timely. 4. It is a high risk for discharging test. 5. Its 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, its 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 cant go through thecapacity 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 andmake the regular capacity test. Most find its discharging capacity cant meet thedesign demand just when power is off. Some battery packs go on working even if it islower than 50% of the rated capacity. It implies that the user of lead acid batteryneeds to monitor the performance status at any time online. Its very important forusers to monitor the performance of lead acid battery. To make full use of lead acidbatteries, we should learn more useful information to maintain them.E T E Dept. GIMT iv
  6. 6. 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 21 Characteristics 3 Pin connections for CD4047 25E T E Dept. GIMT v
  7. 7. 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 27E T E Dept. GIMT vi
  8. 8. CONTENTS Acknowledgement iii Abstract iv List of Tables vi List of Figures viiChapter 1 INTRODUCTION 1Chapter 2 BLOCK DIAGRAM 2Chapter 3 BATTERY MONITORING SYSTEM 3Chapter 4 CHARGING SYSTEM 8Chapter 5 INVERTER 13Chapter 6 CONCLUSION 15Chapter 7 FUTURE SCOPE 16 Appendix 1: Datasheet of BMS Appendix 2: Datasheet of Charging System Appendix 2: Datasheet of Inverter BibliographyE T E Dept. GIMT vii
  9. 9. CHAPTER 1. INTRODUCTION Modern industrial, energy generation and distribution, medical, telecom andtransportation systems depend more and more on batteries. Battery Monitors aredesigned to provide information about one’s battery bank. In our project, we have made an analog battery monitoring system to monitora 12v lead acid rechargeable battery. Also it is necessary to recharge the battery hencewe have developed a charger circuit to perform charging of the battery, the battery isalso used as a source of an inverter. The inverter circuit converts dc voltage to acvoltage. The main objective of this project is to increase the maintenance and utility ofa 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 holdinverter or ups system to monitor the status of the battery constantly. As soon as thevoltage 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 cutoff and the BMS starts its work again.E T E Dept. GIMT Page 1
  10. 10. CHAPTER 2. BLOCK DIAGRAM Fig.2.1. Basic 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.E T E Dept. GIMT Page 2
  11. 11. CHAPTER 33.1. BATTERY MONITORING SYSTEM The BMS is an ultralow power ten LED battery voltmeter circuit that isoptimized for monitoring charged 12V battery systems. The circuit features anexpanded meter scale that displays ten color-coded voltage steps from 10.5V to15.0V. Power is conserved by only turning on the appropriate LED for a short butbright 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 inthis mode. The BMS also includes a battery low voltage beeper that warns when thebattery voltage drops below a pre-set voltage. The beeper can be turned on and offwith the L.V. Beep Activate switch. The BMS is protected against reverse voltageconnection and is fused for safety. The BMS circuit is designed to work inconjunction with both the SCC3 Solar Charge Controller and the SPC3 Solar PowerCentre.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.E T E Dept. GIMT Page 3
  12. 12.  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.E T E Dept. GIMT Page 4
  13. 13. 3.2. CIRCUIT DIAGRAM Fig. 3.1. Circuit Diagram of BMSE T E Dept. GIMT Page 5
  14. 14. 3.3. THEORY 12VDC power is supplied to the BVM circuit via a two pin screw connector; itis routed to the rest of the circuit through fuse F1. Diode D1 protects the circuit fromthe application of reverse battery polarity on the input. Capacitor C1 filters out highfrequency noise from the power input. With the Calibrate switch off, timer IC1 produces a low duty cycle pulse on itsoutput, pin 3. If the Calibrate switch is turned on, the IC1 output stays on. The outputsignal is sent to MOSFET Q1, which turns the negative-side power bus of the IC2voltmeter and the beep circuit on and off. The LM3914N voltmeter, IC2, is wired as an expanded scale voltmeter with anominal voltage display from 10.5 to 15.0V in .5V steps. All of the LEDs will turn offbelow 10.5V and the 15.0V LED will stay on at 15.0V and above. Potentiometer VR1adjusts the voltage span covered by IC2 and potentiometer VR2 adjusts the voltagepoint 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. BeepActivate switch. IC4 provides a steady 5V reference. IC3a is wired as a comparatorcircuit with hysteresis. IC3a compares the 5V reference to the battery voltage, whichis scaled to a value near 5V by R7, VR3 and R8. When the scaled battery voltage fallsbelow the reference voltage, the output of IC3a goes low and turns on IC3b, a 3 kHzsquare 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 turnthe Calibrate switch off and turn the L.V. Beep Activate switch on. We observe thebattery voltage on the differently coloured LEDs. If the battery voltage falls below thewarning threshold, the beeper will sound in conjunction with the LED flashes. TheL.V. Beep Activate switch can be turned off to silence the beeping. For a constantlyon LED display, we turn the Calibrate switch on.E T E Dept. GIMT Page 6
  15. 15. E T E Dept. GIMT Page 7
  16. 16. CHAPTER 44.1. CHARGING SYSTEM Before we go into the operation of the SLA Battery Charger circuit, there are anumber of points we need to cover about the care and use of Sealed Lead Acidbatteries. Firstly, these batteries must be charged, discharged and stored verycarefully. We normally think batteries can be stored for months (if not years) and theywill be available for immediate use. This is not the case with SLA batteries. If we store a NEW, full charged SLAbattery for 6 months or more, we will find that it may be fully discharged. We mayalso find that we cannot charge it even. It may be worthless. Thats how delicateSLA batteries are. They must be charged on a regular basis to prevent themdischarging to a very low voltage level. If the terminal voltage of a SLA battery isallowed to go below 8V, a process called SULPHATION starts to cover the surface ofthe plates and prevents the battery being re-charged. The internal resistance of thebattery 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 lessthan 4 volts. If you have a good battery that has been totally discharged, you canmanually 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 normalway once the voltage rises more than 4 volts.E T E Dept. GIMT Page 8
  17. 17. 4.2. CIRCUIT DIAGRAM: Fig. 4.1. Circuit Diagram of Charging System4.3. THEORY The circuit consists of 5 building blocks. The circuit does not turn on until abattery is connected across the terminals as shown in the diagram. A push switch hasbeen provided to start the circuit when a totally flat battery is fitted. This action turnson 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 bottomrail of the circuit goes through a signal diode, the gate-cathode junction of the SCRand 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 anAC supply as we do not want any electrolytes to be present on the power rail as thisE T E Dept. GIMT Page 9
  18. 18. will allow a very high charge-current to flow and possibly damage the SCR. A DCsupply will not allow the SCR to turn off, as it turns off when the current through itfalls to zero. The circuit is actually a half-wave rectifier. It only charges the battery onevery half cycle. The plug pack doesnt like this as it leaves residual flux in the core ofthe transformer and causes it to overheat. But thats the only drawback with thecircuit. The SCR turns on during each half cycle and current flows into the battery. Avoltage is developed acrossthe two 1R8 resistors (inparallel) and this voltage is fedinto the 47u electrolytic. Itcharges and turns on theBC547 transistor. Thetransistor robs the SCR of gatevoltage and the SCR turns off.The energy in the 47u feedsinto the transistor but after a Fig. 4.2. Block Diagram of Charging Systemshort time it cannot keep thetransistor turned on. The transistor turns off and the SCR switches on and deliversanother pulse of current to the battery. As the battery charges, its voltage increasesand this is monitored by the "Voltage Monitor" block. The circuit is very complex and one way to look at the operation is to considerthe top rail as a fixed rail and as the battery voltage increases, the rail connected to thenegative 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 voltagedrops across each of them. The "Voltage Monitor" components consist of a transistorand zener diode as well as an 8k2 resistor, the 1k pot, a 1k5 resistor, a 150R resistorand a signal diode. The signal diode is actually part of the flasher circuit and wediscuss 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 thatcorresponds to the resistance of the resistor. The diode will have a constant 0.7Vacross it. The voltage on the wiper of the pot will be about 3.25V and the voltageacross the zener will be 10V. This leaves 0.6V between the base and emitter of theE T E Dept. GIMT Page 10
  19. 19. Voltage Monitor transistor. This voltage is sufficient to turn the transistor ON. Whenthe 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 isturned on, the battery gets a high pulse of current and the current is only limited bythe capability of the plug pack. There are no electrolytes to allow very high pulses ofcurrent to be delivered and this is fortunate as the SCR is only a 0.8 amp device, butwill endure surges of 10amp for half a cycle. Whenever the SCR is triggered intoconduction during the half cycle of its operation, it remains in conduction until thevoltage delivered by the plug pack falls to zero. This is when the SCR turns off. Whenthe plug pack delivers a negative voltage to the top rail and a positive voltage to thelowest rail, the SCR is not triggered into conduction and none of the components inthe 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 currentdelivered 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 and47u (connected to the voltage monitor section). When the battery is charging, the 47uis charged via the diode connected to the BC557 transistor and through the 150R andsignal diode to the negative of thebattery. When the battery is fullycharged, the Voltage Monitor sectionturns ON and turns off the "Turn ON"section. This removes the voltage on thepositive side of the 47u and the positiveside is brought to the negative rail viathe 2k2 resistor. This brings down the Fig. 4.3. Voltage Monitoring Sectionnegative side of the 47u and the 150Rresistor is allowed to drop below the negative rail due to the presence of the diode, asthe diode becomes reverse-biased. This holds the circuit in the "off" condition, as theE T E Dept. GIMT Page 11
  20. 20. 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 ofcurrent into the battery to keep it charged. This is called "Trickle Mode" or "PulseMode."E T E Dept. GIMT Page 12
  21. 21. CHAPTER 55.1. INVERTER An inverter is circuit which converts a dc power into and ac power at desiredvoltage and frequency. The ac output voltage could be fixed, at fixed or variablefrequency this conversion can be achieved either by control turn on and turn offdevices as for example BJTs and MOSFETs. Inverters can be classified according tothe wave shapes of the output voltage they are: square wave inverter, quasi squarewave inverter and pulse width modulated inverters. In this project we have made asquare wave inverter which produces a square wave ac voltage of a constantmagnitude. The output voltage of this type of inverter can only be varied bycontrolling the dc input voltage. Such inverter is adequate for low and medium powerapplications.5.2. CIRCUIT DIAGRAM Fig. 5.1 Circuit Diagram for InverterE T E Dept. GIMT Page 13
  22. 22. 5.3. THEORY Here is the circuit diagram of a simple 100 watt inverter using IC CD4047 andMOSFET IRF540. The circuit is simple low cost and can be even assembled on aVero 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 whichare 180 degree out of phase at the pins 10 and 11 of the IC. Pin 10 is connected to thegate of Q1 and pin 11 is connected to the gate of Q2. Resistors R3 and R4 preventsthe loading of the IC by the respective MOSFETs. When pin 10 is high, Q1 conductsand current flows through the upper half of the transformer primary which accountsfor the positive half of the output AC voltage. When pin 11 is high Q2 conductsand current flows through the lower half of the transformer primary in oppositedirection and it accounts for the negative half of the output AC voltage.E T E Dept. GIMT Page 14
  23. 23. CHAPTER 6CONCLUSION We hereby conclude that, in our project the main aim was to develop “AnAnalog Battery Monitoring and Charging System”. We have succeeded in making theBMS and tested in a 12V SLA (Sealed Lead Acid) battery which works fine. Furtherwe have tried to add some additional circuitry to our project, so that besidesmonitoring it also provides some sort of management and utilisation of the battery andthat’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 foundthat the output power is too low and it can only be used to light up a simple Neonlight, so now the remaining work is to increase the output power of the inverter andassemble all the circuits (i.e. Battery Monitoring System, Charging System and TheInverter) so that we can make a complete commercial UPS which will provide usapproximately 45W power. Taking a look at these goals at the end it can be said that the total cost of ourproject was approx. Rs. 3000/- (INR). This project is a stepping stone to a cheaper andefficient battery monitoring system along with 12v battery charger and inverter.E T E Dept. GIMT Page 15
  24. 24. CHAPTER 7FUTURE SCOPE The BVM is an ultralow power ten LED battery voltmeter circuit that isoptimized for monitoring charged 12V battery systems. So it is like an analogvoltmeter which continuously measures or monitors the status of the battery anddisplay the result by glowing the LEDs of different colours. So the user must knowthe meaning the LED colours i.e. he should know which colour represents how muchvoltage drop. So if we can make the display digital, then the user interface willdefinitely increases. But eventually the cost will also increase. Again, since the designwas constructed to monitor the car battery, it will be very handy if we can attach thecircuit on the car dash. So further research and planning also would be placed on thelocation of the BMS with respect to where the ON/OFF switch and indicator lightwould be installed on the car dash. Similarly during testing we noticed that theinverter output power changes with component specifications. That’s why there is apossibility of increasing the output power level of the inverter if we can devote moretime on testing the components.E T E Dept. GIMT Page 16
  25. 25. Appendix 1: Datasheets for BMS 1. TLC555CP: Fig. 1. Pin Diagram of TLC555CP 1.1. SPECIFICATIONSE T E Dept. GIMT Page 17
  26. 26. Fig. 2. Functional Block Diagram of TLC555CP Table 1. Electrical Characteristics at VDD=5VE T E Dept. GIMT Page 18
  27. 27. 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 voltagesE T E Dept. GIMT Page 19
  28. 28. 3. 2N7000: Fig. 4. 2N7000E T E Dept. GIMT Page 20
  29. 29. Appendix 2: Datasheets for Charging System 1. MCR100-6: Fig. 5 Pin Diagram of MCR100-6 Table 2. Maximum Ratings and Electrical CharacteristicsE T E Dept. GIMT Page 21
  30. 30. 2. BC547: Fig. 6. Pin Diagram for BC547E T E Dept. GIMT Page 22
  31. 31. E T E Dept. GIMT Page 23
  32. 32. 3. BC557: 1. Collector 2. Base 3. Emitter Fig. 7. Pin Diagram for BC557E T E Dept. GIMT Page 24
  33. 33. Appendix 3: Datasheets for Inverter 1. CD4047: Fig. 8. Pin Diagram for CD4047 Table 3: Pin Connections for CD4047E T E Dept. GIMT Page 25
  34. 34. E T E Dept. GIMT Page 26
  35. 35. 2. P55NF06: Fig. 9. Pin Diagram for P55NF06E T E Dept. GIMT Page 27
  36. 36. 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. 5. 6. 7. http://www.datasheet4u.comE T E Dept. GIMT Page 28