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T.C
DOKUZ EYLUL UNIVERSITY FACULTY OF ENGINEERING
ELECTRICAL & ELECTRONIC ENGINEERING DEPARTMENT
LITHIUM POLYMER BATTERY CHARGER
WITH
50 Hz 220V AC SUPPLIES
Final Project Thesis
by
Özgür Mehmet Duman
Advisor
Prof. Dr. Haldun Karaca
June, 2011
IZMIR
THESIS EVALUATION FORM
We certify that we have read this thesis and that in our opinion it is fully adequate, in
scope and qualify as an undergraduate thesis, based on the result of the oral examination
taken place on …/.../2011.
…......................................... Prof. Dr. Haldun Karaca
(Advisor)
…......................................... …………………………… Prof. Dr. Eyüp Akpınar Assist. Prof. Dr. Özge Şahin (Committee Member) (Committee Member)
Prof. Dr. Gülay Tohumoğlu
(Chairman)
ÖZET
Elektrik şebekesine uzak olan sistemler, yerdeğiştirebilen elektrikli araçlar ve taşınabilir
elektronik cihazlar, akü enerjisi ile çalıştırılabilirler. Lityum bazlı aküler, hafif ağırlıklara
sahip olmalarına rağmen, yüksek enerji ve yüksek güç yoğunluklarına sahip olduklarından
dolayı kullanım alanları çok geniştir. Lityum bazlı akülerin kullanım sürelerinin azalmasını
engellemek için akü kataloglarında belirtilen şarj yöntemlerine uygun veya daha üstün olan
şarj cihazlarıyla şarj edilmelidirler.
Yapılan projenin amacı, mikrodenetleyici kontrollü bir şarj cihazının tasarlanıp,
üretilemsidir. Dokuz Eylül Üniversitesi Solaris Güneş Arabası Takımı’nın lityum polimer
akülerini, 50Hz 220V alternatif akım sağlayabilen elektrik enerjisi kaynağı ile şarjını
sağlatabilecek bir güç elektroniği bazlı devre kurulmuştur. Elektronik devre içerisinde
alternatif akımdan doğru akıma çevirici, akü şarj akımı ve voltajı geri bildirimlerine göre
mikrodenetleyicinin anahtarlamayı kontrol ettiği, anahtarlamalı artıran doğru akımdan doğru
akıma çevirici içermektedir. Devre dizaynı için Matlab R2009b’nin Simulink araçı ve
Proteus 7.7 devre simulasyon programı kullanılmıştır.
ABSTRACT
Generally electric vehicles and portable electronic equipments are supplied with battery
systems. Lithium based batteries have initiatives because of their high energy density and
high power density features. But lithium batteries are required suitable chargers, which can
charge due to charge characteristic at battery datasheet, for more cycling life and be
protected heating, overcharging…etc.
In this project, a microcontroller controlled battery charger was designed and realized on
lithium polymer batteries of Dokuz Eylul University Solaris Solar Car Team. Charger is
included with AC to DC converter, step up DC to DC converter, monitoring systems of
converters and battery charge level by microcontroller. The design is simulated with Matlab
R2009b Simulink and Proteus 7.7 simulation programs.
TABLE OF CONTENTS
Thesis evaluation Form........................................................................................................i
Özet................................................................................................................................... ii
Abstract...............................................................................................................................iii
Table of Contents................................................................................................................iv
List of Figures........................................................................................................ ………vi
List of Tables..................................................................................................................... vi
CHAPTER ONE
1. INRODUCTION………………………………………………………….............1
CHAPTER TWO
2. BATTERY CHARGING………………………………………………………….2
2.1 Lithium Polymer Batteries …………………………………………...2
2.2 Battery Chargers ……………………………………………………..4
2.3 Charging Algorithm…………………………………………………..6
2.4 Determine State of Charge…………………………………………...7
2.5 Flow Chart…………………………………………………………….8
CHAPTER THREE
3. CHARGER TOPOLOGY ………………………………………………………..9
3.1 Ac to Ac Converter...............................................................................10
3.2 Rectifier………………………………………………………………..11
3.3 Full Wave Rectifier Circuit……………………………………….....12
3.4 Filters………………………………………………………………….13
3.5 Dc to Dc Converters………………………………………………….13
3.5.1 Determining Components of Boost Converter Circuit…….14
3.6 Microcontroller……………………………………………………….15
3.7 Hall Effect Sensor…………………………………………………...16
3.8 Voltage Divider Circuit………………………………………………17
CHAPTER FOUR
4. RESULTS…………………………………………………………………………18
4.1 Matlab Simulink Simulation…………………………………………18
4.2 Progress Up to Date………………………………………………….19
4.2.1 Battery Management System…………………………………19
4.2.2 Lead Acid Battery Charger…………………………………...20
4.2.3 Mobile Robot and Lithium Polymer Charger……………….20
4.2.4 Preparing Look Up Table for SoC……………………………21
CHAPTER FIVE
5. POWER CALCULATION………………………………………………………22
6. CONCULUSIONS………………………………………………………………24
7. REFERENCES…………………………………………………………………..25
8. APPENDICES…………………………………………………………………...26
A. Cost of Project……………………………………………………………..26
B. Time Table………………………………………………………………….27
C. Schematic of Project………………………………………………………..28
D. Codes………………………………………………………………………..29
E. Datasheets…………………………………………………………………...31
TABLE & FIGURE LIST
Table1: Comparison of battery types …………………………………………………………………2
Table 2: Characteristic parameters of SLPB55205130H coded battery …………………………3
Table 3: Charger types and their features…………………………………………………………. 5
Table4: History of SoC measuring is given in table …………………………………………….7
Table 5: Features of 16f877 MCU …………………………………………………………….. 15
Figure 1: Charge levels of Lithium polymer battery …………………………………………….4
Figure 2: Cycle changing due to discharge capacity………………………………………………5
Figure 3: Basic charging steps ………………………………………………………………………9
Figure 4: Transformer outer and inner appearing………………………………………………..10
Figure 5: Power electronic switches performances………………………………………………11
Figure 6: Full wave rectifier diode bridge schematic, output waveform and package in project .12
Figure7 : KBU801 Bridge rectifier instantaneous forward voltage and current………………..12
Figure 8: Microcontroller controlled boost converter …………………………………………..13
Figure 9:Waveforms for boost converter operating …………………………………………….13
Figure 10: Pwm signal shape and formulation of Pwm period……………………………...15
Figure11: Acs712 hall effect sensor and application circuit…………………………………….16
Figure 12: Voltage divider circuit…………………………………………………………………..17
Figure13: Schematic of system in Matlab Simulink ……………………………………………18
Figure 14: Output voltages of rectifier end boost converter…………………………………….18
Figure 15-16: Battery management systems of 60V lead acid batteries………………………..19
Figure 17-18 Parts of lead acid 6V battery charger and working device………………………..20
Figure 19-20: Lithium battery supplied mobile robot and battery monitoring station ……….20
Figure 21-22 Charging lithium batteries one by one…………………………………………….21
Figure 23-24 Lead Acid 60V batteries charging. ……………………………………………….21
Figure25: AC-DC converter part of Charger…………………………………………………….22
Figure 26:Maximum power transferring model circuit…………………………………………22
Figure 27: Boost converter schematic of project………………………………………………….....22
CHAPTER ONE
1. INTRODUCTION
Nowadays electric energy is used for creating more easy life and clean environment. Also
this energy type using goes on with increasing acceleration because of being global warning
problem solution. Day by day technology is developed and used within the life. That’s why
all energy conversion to electrical energy must be cheaper, more efficient and suitable to use.
Battery is a kind of electrical energy suppliers and takes place in life within small or big
electrical applications. Portable devices’ increasing (e.g portable computers, personal data
assistants, cellular phones, shavers etc.) causes accelerating to notice of batteries position in
our life. Other electrical devices, which contain high battery technology, are electrical
vehicles (EV). Electric vehicles have electric motors and batteries provide exciting energy
for electric motor driving. Battery companies and scientists separate too much budget and
time to developed battery technology. That’s why battery types and power electronic battery
testing machines are developing day by day.
Although battery using is common, changing of aging batteries’ cost and recycles are the
biggest handicaps of buying battery supplied devices. Wrong battery charging and
discharging methods are important factors which decrease cycle amount of batteries. Smart
battery chargers are developed to reduce aging with correct charging process.
In this project lithium polymer batteries of Solaris Solar Car Team are charged with
220Volt (V) alternative current (AC) electrical supplies. Full wave rectified AC/DC
converter, boost type direct current DC/DC converter, 250Watt (W) transformer and
microcontroller, which determines charge steps due to flowing charge current and battery
voltage, are contained in charger circuit topology. All systems are simulated one by one then
altogether with Matlab Simulink. State of charge determination until charging time is another
important part of the project, so lookup tables are created due to battery, too. Comparing
commercial charging devices due to efficiency and cost analysis is realized for project.
CHAPTER TWO
2. BATTERY CHARGING
2.1 Lithium Polymer Batteries
Lithium polymer battery is included families of electrolyte type batteries. This feature
differentiates it from other battery types. The original design, dating back 1970s, uses dry
solid polymer electrolyte only. This electrolyte resembles a plastic like film that it does not
conduct electricity but allows an exchange of ions. The polymer electrolyte replaces the
traditional porous separator, which is soaked with electrolyte [1]. After improving on battery
technology, li-polymer batteries are obtained superior features, light weight, small package,
high energy density, low self discharge and low maintenance, although they have some
limitations, expensive, high technology battery charger requirements.
Table1: Comparison of battery types [2].
Battery companies test battery limitations and create characteristic parameters for
effective usage. These parameters presented in characteristic table in table 2.
Table 2: Characteristic parameters of SLPB55205130H coded battery [3].
The project battery package is created with 15 series battery cells. Total nominal voltage
is calculated 15x3,7=55.5V. Total maximum charge voltage 15x4.2=63V (Batteries mustn’t
be charged above this value.) Total minimum cut-off voltage is 15x2.7=40.5V (Batteries
mustn’t be discharged below this value.) These voltage levels are critical to prevent
hazardous on batteries. That’s why lithium based batteries mustn’t be connected electric
energy sources directly also discharge control devices are used between load and battery to
control parameters until discharging process.
Another charge parameter is C rate. Charge and discharge current values of a battery are
measured due to C rate. For example, a battery, whose rated value is 1000miliamperehour
(mAh), provides 1000mA for one hour if discharged at 1C rate. The same battery discharged
at 0.5C provides 500mA for two hours [1].
Li-po batteries are usually charged at 1C value in 2 hour. In this project li-po batteries would
be charged at between 0.5A~4A in approximately 4 hour due to our battery cell
characteristic. Batteries are defined 5.5Ah at 0.5C in cell specification table. So hardware
and software of the project will designed like providing approximately maximum 240W
power to battery according to charge algorithm to realized levels of charge in figure 1.
Figure 1: Charge levels of Lithium polymer battery [3].
2.2 Battery Chargers
Battery chargers are classified due to using charge rate of charge process. Chargers of
lithium based batteries have three branches;
1. Rapid Chargers
2. Fast Chargers
3. Ultra Fast Chargers
Charge times are different each type of chargers. In project design is classified as rapid
charger type because of charger charge rate is changed between 0.1C and 0.5C in table3.
Also
low
charge
rated
charging is recommended by battery companies because of aging is slowed down and cycles’
amount is increased figure 2.
.
Figure 2: Cycle changing due to discharge capacity.[4].
Table 3: Charger types and their features. [4].
All charger classes can be realized by different topologies. Thus chargers are grouped as
supbranches due to charger topologies.
Battery charger topologies;
Simple Trickle Timer-based Intelligent Fast Pulse Inductive USB-based
Solar chargers
The charger of project is a type of pulse charger. Because of output voltage is adjusted for
constant current by switching operations, low power dissipation occurs on switches in
addition charger technology have a tendency to pulse chargers. Some scientists for example,
Pratik Mukherjee and working friends worked on buck boost converter system with galvanic
insulation for Lead Acid batteries, B. J. Masserant and working friends boost buck converter
system for Nickel Metal batteries, M.F.M. Elias and working friends designed a charger with
balancer for Lithium Ion batteries.[5]
The circuit design of project was realized by electronic components which are get by
advisor and located laboratory. So charger output requirements, power and efficiency
calculations are due to these components.
2.3 Charging Algorithm
Efficient charging process is dependent a lot of parameters. Datasheets of batteries
provide graphics charging characteristics due to time, temperature, aging …at different
charge rates. These graphics create fundamental knowledge of charging steps and rules in
figure1 and table2. But batteries characteristics change due to aging and usage types day by
day. So charge steps determination necessities battery’s state of charge information
continuously.
2.4 Determine State of Charge
State of charge (SoC) is information of storage energy in battery at charging or
discharging process. SoC affects efficiencies of these processes measurements directly.
Because algorithms of battery measuring systems follow SoC value to determine how much
time is remained to finish of charge. Some methods were developed to get SoC info, but for
SoC measuring, methods, which are in table3, are used together to read effective value.
In 1984, Peled developed a method for determining the SoC of lithium-ion batteries. At
the base of the presented method are predetermined voltage and temperature measurements,
used as input parameters for look-up tables. After applying a current step and a short resting
period, the OCV and the temperature of a battery are measured. The measured value is
compared with a corresponding predetermined value stored in a look-up table. Based on this
comparison, the SoC is indicated. In the system of Kopmann (1987) the terminal voltage, the
current and time are measured during each battery charging and discharging cycle. These
values are also used as inputs for look-up tables. [6]
Table4: History of SoC measuring is given in table[6].
In this project, following look up table method is tried with constant current (CC)
and constant voltage (CV) charging method which is determined in datasheet of battery.
Also overcharging problem is prevented of CV stage of charging.
2.5 Flow Chart
CHAPTER THREE
3. CHARGER TOPOLOGY
In project, electronic system was planned due to fundamental energy transmission.
Firstly lithium polymer battery characteristic features are determined then hardware
requirements are studied. Overall the charging process can be defined in figure 3. In
addition to block diagram, charging controlled by a microcontroller, because of battery
limitations.
Microcontroller(MCU)
Pulse Switching
Figure 3: Basic charging steps [7].
3.1 Ac to Ac Converter
In this project, the charger circuit uses grid energy for battery charging. So firstly AC-AC
converter is designed.
These converters are used to adjust from AC voltage value as input to different AC
voltage value as output. This converting operation can be realized by transformers, TRIAC
and other power electronic elements. Providing isolation, availability and reliability are
advantages of transformers’ usage. That’s why transformer is used in this project.
Transformers are created by two independent coils. When primary side of transformer
connected to electric grid, magnetic field is created. Then this magnetic field causes voltage
induction on secondary side of transformer due to Faraday Law.
e ind=Ndφdt
{N:Number of turn, φ:Flux, e ind : : Induced voltage } (1)
[8]
Figure 4: Transformer outer and inner appearing.[8]
Transformers can be used in low power, low current electronic and control circuits for
performing such functions as matching the impedances of a source and its load for maximum
power transfer, in addition circuit isolation and direct current isolation while maintaining ac
continuity between two circuits are other usage purposes [8].
In charger circuit approximately 250 Watt transformer is chosen to effectively charging
process at 0.5C (4A for 63 V battery modules). Grid electric voltage (220V rms) is stepped
down to 30Vrms and rectified. Efficiency calculation of transformer is required rated values of
transformer and open circuit and short circuit test. Losses were neglected. Because lack of
name plate of transformer.
∩;= IsxVscosθPcu+Pcore+ IsxVscosθ
x100 {Is: Seconder current Vs:Seconder voltagecosϴ:power factor Pcu:Copper loss Pcore:Core loss } (2),
[8]
3.2 Rectifier
Rectifiers’ purpose is obtaining dc from ac gird connection. Rectifiers are branch out
controllable and uncontrollable. Uncontrollable type rectifiers are including diode
combinations. So output of the rectifier is change due to AC input’s change as out of user
control. Their losses and voltage decreases are high so some application, which efficiency is
most important for system, diode bridge rectifiers are not preferred.
Controllable
types rectifiers have
switching elements,
like tristor, mosfet,
IGBT…They
provide low power
loss and minimum
harmonics, also alternative solutions are prepared with them to lower size circuits without
transformers.
Figure 5: Power electronic switches performances [9].
Design of controllable rectifier circuit prevent finishing the project in time, full wave
rectifier circuit with diode is used in project although lack of efficiency.
3.3 Full Wave Rectifier Circuit
Full wave rectifier circuit is used to get rectified output voltage of transformer. Internal
junction capacitors (250pF) of full wave rectifier circuit provide rippled positive and
negative dc voltages as an output. After filtering these voltages are be able to supplied
needed systems.
Figure 6: Full wave rectifier diode bridge schematic, output waveform and package in project [9] [11]
V R (t )={ vS (t )=V 0 sin wt vS (t ) ≥ 0vS (t )=−V 0 sin wt v S (t )<0
(3)
V DC=( 2π)V 0 (4) [9]
Transformer output is equal to 30Vrms, this value espresses Vdc of sinusoidal signal ,
after full wave rectifier diodes Vo is equal 43V peak value of rectified signal. Output
capacitor shapes rectified signal to rippled dc form.Maximum power dissapation of rectifier
diodes is 4Watt, because maximum output current is determined as 4 A and induced voltage
for this current is equal approximately 1V due to figure 7 from datasheet.
PD=I F x V F (5 )[10 ]
Figure7 : KBU801 Bridge rectifier
instantaneous forward voltage and current. [11]
3.4 Filters
In AC to DC applications, current and voltage values have instantaneous changing
because of load or source characteristic behaviors. These unwilling affects are absorbed by
filter circuits for preventing system hazardous and efficiently running.
Output of full wave rectifier is connected to first order low pass filter. Also boost
converter has internal low pass filter too. Switching process causes current and voltage
harmonics output of converter circuit. So filter elements must be determined due to provide
that corner frequency f0 lower than switching frequency fs.
fo< fs fo= 1
2√LC (6) [12]
fs is equal to 10kHz in this project 400uH and 470uF are inductor and capacitor values. So
fo is calculated as 1,153kHz.Capacitor and inductor value is proved equation 6.
3.5 Dc to Dc Converters
The switching power supply market is flourishing quickly in today’s high-tech world.
Design engineers aren’t always supplied with the desired amount of voltage they need in
order to make their design work. Adding an additional voltage supply to a design is not
always cost efficient.
Efficiency, size, and cost are the primary advantages of switching power converter when
compared to linear converters. Switching power converter efficiencies can run between 70-
80%, whereas linear converters are usually 30% efficient. The DC-DC Switching Boost
Converter is designed to provide an efficient method of taking a given DC voltage supply
and boosting it to a desired value.[13]
Figure 8-9: Microcontroller controlled boost converter [14]. Waveforms for boost converter operating [15].
In project low voltage input is increased to Vtotal maximum charge voltage (63V) by step
up (boost) dc to dc converter like in figure 8. A simple boost converter consists of an
inductor, a switch, a diode, and a capacitor. Boost converter circuit works two modes. Mode
1 begins when the switch (SW) is turned on at t = Ton, Mode 2 begins when the switch is
turned off at t = Toff. The current that was flowing through the switch would now inductor
L, diode D, capacitor C, and load R [15].
3.5.1 Determining Components of Boost Converter Circuits
Designed boost converter circuit has higher switching frequency (10kHz) than grid
electricity frequency (50Hz), so designing L C passive filter, which is used for absorption of
input voltage ripples, can be eliminated for input of boost. Switching process creates own
ripples on output so boost converter elements must be chosen for bottom formulations.Vout
is the output voltage, k is duty cycle, and Vin is input voltage.
Vout=( 11−k )Vin (7) [16]
Lmin is the minimum inductance, R is output resistance.
Lmin=((1−k )2kR2 f ) (8)
Vr is output voltage ripple factor.
Vr=∆ VoutVout
(9)
Cmin is the minimum capacitance k is duty cycle , and f is the switching frequency of switch
[12].
Coutmin=k Iout (max)
f ∆ Vout (10)
In project switching frequency is determined 10 kHz and 43Vdc input voltage is
increased to 63Vdc so duty value (k) is obtained 0.32. Battery internal resistance is estimated
as 8mΩ for each cell so battery package has 90mΩ. Lmin is calculated as 74uH and also
voltage ripple factor is equal 1.6mV for 0.1 Voutput voltage ripples, Cmin is 1200uF
approximately. Power diodes and power mosfet are chosen which have fast reactive to
switching process. Because duty changing must be realized effectively to get expected output
voltage. In addition, high current capability mosfet is used for switching for least heating
power dissipation on mosfet. But MCU’s trigger signal couldn’t effect to mosfet so
triggering signal is amplified by darlington transistor combination.
3.6 Microcontroller
Microcontrollers (MCU) are the most popular electronic devices because of simple usage
and cheap cost. RAM, ROM, ADC etc. electronic devices are located in same package. A lot
of applications can be realized by microcontroller.
Table 5: Features of 16f877 MCU[17]
In project, MCU provides obtaining charge current and charge voltage data by external
hall effect sensor and voltage divider circuit as analog voltage values. 16f877 has 10 bit
ADC unit so 0.0048V (resolution of ADC) changing causes changing least significant bit
(LSB). Then MCU arranges charging process due to charge algorithm.
Boost converter output voltage is modulated mosfet switching by MCU. Pulse width
modulation module of MCU provides pulses for switching mosfet at determined frequency
and determined width while other applications go on.
PWM period=( PR 2+1 )∗4∗T osc∗TMR 2 prescale(11)
Figure 10: Pwm signal shape and formulation of Pwm period. [17]
In project MCU is run with 4Mhz crystal oscillator. Pwm frequency is adjusted as 10kHz
due to formula 10.
setup_ccp1(CCP_PWM); //ccp1 module is chosen for pwm output
setup_timer_2(T2_DIV_BY_1,99,1);//timer2 division value,PR2,prescaler
set_pwm1_duty(duty); //duty can be any integer between 0 and 400 due to formula 11
T pwmduty=(duty value ) .T osc (Timer 2 division value ) {T pw mduty
<T osc }❑(11) [17]
3.7 Hall Effect Sensor
In this project current values of charging are measured by hall effect sensors of Allegro
firm. Hall effect sensors work by magnetic induction on material due to the flowing current.
Flux increases due to the increasing current value; hence induced voltage is appeared at the
output of current sensor.
Low costs and small packages of these sensors are attractiveness properties. In addition,
only 5 volt is enough to supply the sensor, so creating different hardware to provide supply
voltages isn’t necessary.
Acs712 hall effect current sensor is loaded near output connector of charger, resolution is
changed between 66mV/A and 185mV/A. In addition extra circuit element must be
connected, they are determined overall schematic.
Figure11: Acs712 hall effect sensor and
16F877 MCU has bit ADC device so its resolution 4.887mV/Bit, minimum resolution of
sensor ( 0.07 A current changing) increases one bit LSB of ADC. So ADC output is
multiplied with sensor and ADC resolutions to obtain real current value.
3.8 Voltage Divider Circuit
Battery voltage is divided to voltage which is smaller than supply voltage of MCU. Maximum charge voltage is 63V so 5/65 voltage divider circuit provides maximum voltage of battery as 4.8V. ADC output is multiplied resolution and 65/5 again to obtain voltage data.
Figure 12: Voltage divider circuit.
Lithium Polymer Battery CHARGER
CHAPTER FOUR
4. RESULTS4.1 Matlab Simulink Simulation
Figure13: Schematic of system in Matlab Simulink
Matlab’s battery model is adjusted as Lithium ion batteries with parameter of project batteries characteristic instead of creating battery models with capacitors with resistors. SoC
value is adjusted as %10, so battery voltage is approximately 40V at simulation result graphs in figure 14.
Figure 14: Output voltages of rectifier end boost converter.
4.2 Progress Up to Date
Project realizing was divided steps for creating most efficient system. All steps were defined
time table of project in appendix. But some delay came into existence because of extra
project. Firstly battery management system was realized for Microcontroller Module. Then
6V lead acid battery charger was designed for Embedded Systems Module. After that a
mobile robot was created whose energy was supplied by 15V lithium polymer battery and
charge station of this battery was realized. Finally 60V lead acid batteries charger was
designed and charge voltage, current, time values were measured of 100V lithium polymer
batteries.
4.2.2 Battery Management System
Figure 15-16: Battery management systems of 60V lead acid batteries.
Battery management systems measure each voltage values of batteries and discard
distorted battery if any. Unless the distorted battery doesn’t provide energy to the system,
other batteries’ materials can be damaged and unwanted conditions such as great current
increment and unbalanced voltage levels can be occurred. BMS provide to prevent these
unwanted conditions. Hence, life of batteries is saved by battery management systems and
maintenance cost of these systems reduces greatly
This project provided to learn electrical connection of batteries, measuring voltages and
currents values each one of 4 series lead acid batteries.
4.2.3 Lead Acid Battery Charger
Figure 17-18 Parts of lead acid 6V battery charger and working device.
In this project main purpose was controlling of all steps of lead acid battery charging. Lm 317 IC doesn’t prove all steps of this project. Only constant voltage charging algorithm is suitable for lm317.
State of Charge couldn’t measure, because of lm 317 couldn’t constant current so constant current charge and discharge characteristic curves anytime intersect with charging curves by lm317. Only constant voltage curves give information about SoC of battery.
The circuit abilities, which were realized, are changing of initial charge current. In addition button configurations provide rock resistance selection which is used for adjustment of the charge current.
4.2.4 Mobile Robot and Lithium Polymer Charger
Figure 19-20: Lithium battery supplied mobile robot and battery monitoring station
In this project, mobile vehicle’s supplying current and voltage measurements were
transmitted to battery monitoring station. In addition this station was able to charge lithium
polymer battery by buck converter.
4.2.4 Preparing Look Up Table for SoC
Figure 21-22 Charging lithium batteries one by one.
Purpose of process was creating look up table for SoC, which provides charge and discharge voltage and current data due to time .
Figure 23-24 Lead Acid 60V batteries charging.
The last revision of charger topology was created. After this experiment power calculation of system was calculated. It was prototype of this project, so all applications were tried on this circuit.
Firstly mosfet driver were designed with two npn type switching transistors as darlington combination. PWM signal was created by MCU for switching small power mosfet in former projects but in this design, 50A power mosfet were used, which is used in final project. So PWM output of MCU is amplified as much as 5625 times Dc current gain.
CHAPTER FIVE
5. POWER CALCULATION
Figure25: AC-DC converter part of Charger
Transformer’s rated power is 250 Watt. But systems impedance must be equal to
transformers internal impedances. Equivalent circuit of transformer can be determined open
circuits and short circuit tests or datasheet.
Figure 26:Maximum power transferring model circuit.[19]
In this project internal impedance of transformer couldn’t calculated because of limited
opportunity. So output power of transformer is estimated as 250Watt. Rectifier diode power
dissipation is maximum 4 Watt .Because 1V is induced on diode while 4A current is
flowing.
Figure
Capacitor power dissipations is neglected.
PL=
12
L1 I peak2
T {PL=power delivered by inductor (W )
L 1=inductor inductance (400uH )Ipeak=max output current (4 A )
T=period of PWM signal (10−4 s) }(12)[20]
PL=32 W
Pdc=V o I peak T off
2T {V o=Adjusted max output voltage (63 V )
Toff =time of switch off ( 6.8 x10−5 s)Pdc=output power whenToff (W ) }(13)[20]
Pdc=87 W
PTotal=Pdc+PL {Ptot=no lossess power (W ) }(14) [20]
Ptotal=119W
PD (L)¿(Ipeak1−k
)2
x Pcu+PLcore {PD (L)=power dissipationof inductor
Pcu=copper loss of inductor (?W )Plcore=core loss of inductor (?W ) } (15)Neglected
PD (Q )¿ ( Ipeak1−k )
2
x RDS (on ) x k
+12
xV 0 x ( Ipeak1−k
)2
(t r+t f )xf s+Qgate xV GS x f s (16) [14]
{PD (Q )=power dissipation of mosfet
Rds=Drai n sourceresistance (0.04 Ω )Qgate=Gatesource capacitance (603 pF )
fs=switching frequency (10 kHz )t r=rise time (60 ns ) t f=fall time(48 ns)
Vgs=Gatesource threshold voltage (4 V )} PD (Q )=0.456 W
PD (Diode)=V D+ I 0 {Vd=diode induced voltage (1 V )Io=max . output current (4 A ) } (17)[14]
PD (diode)=4 W
Boost converter efficiency is approximately %96 in these conditions, but charger efficiency was affected by transformer, rectifier diodes, MCU and regulators.
6. CONCULUSIONS
In this project process, lithium polymer battery characteristics and differences from other batteries were learned. Algorithms of charge operation were originated due to battery information. Charge rate (C), state of charge (SoC) were key positions to determine project hardware and software structures.
Appropriateness of pulse chargers for lithium based batteries is proved due to obtain constant charge current and voltage. Buck and boost types Dc to DC converters are suitable to create pulse chargers because of calculated high efficiency value.
Good quality transformers must be used for supplying more power to converter circuit. Rated values and equivalent circuit parameters must be known to calculate maximum power transferring. Controllable wave rectifiers with IGBTs or mosfets must be used instead of uncontrollable full wave rectifier circuits to low current harmonics and high power factor. Maxim bms chip (MAX11080) and SoC chip (MAX17040) improve the project, too.
MCU must be isolated power electronic circuits by optocouplers. Because power electronic circuits have capacitors, which cause high current peaks, and inductors, which cause high voltage peaks. No isolated circuit can be affected these instantaneous changes. Measurements have high importance is charge process, so interactions must be minimized for stabilization.
7. REFERENCES
[1]BUCHMANN, I., Batteries in a Portable World, pp. 44-95, 2nd Edition, Cadex Electronics
Inc., CANADA, 2000
[2]EV_battery_comprasion.pdf
[3]Kokam Comp.Web page http://www.kokam.com/english/product/battery_main.html
SLPB55205130H_11Ah.pdf 12.12.10
[4]http://batteryuniversity.com/learn/article/all_about_charger
[5]KAYIKLI, T., BALIKÇI, A.,” Elektrikli Araçlarda Kullanılan Lityum-Polimer Aküler
İçin Bir Şarj Cihazı Tasarımı”, Electronic Engineering Department, Gebze High Technology
Institude. pp.1-6
[6]POP, V., Universal State-of-Charge Indication for Portable Applications, pp.13-24, 1st
Edition, University Press Facilities,Eindhoven, NEDERLANDS, 2007
[7]MEGEB ,” ELEKTRİK ELEKTRONİK TEKNOLOJİSİ D.A. GÜÇ KAYNAKLARI VE
MOTORLARI” Turkey Republic Ministry of Education, Ankara, TURKEY, pp. 4, 2007.
[8]FITZGERALD, A.E., KINGSLEY, Jr.C., UMANS, S.D. Electric Machinery pp.58-
112, 6th Edition, McGraw Hill Company, New York, USA, 2003 .
[9]UYAROĞLU, T. Web page: www.uyaroglu.org, 20.10.2009.
[10]HAUKE, B., “Basic Calculation of a Boost Converter's Power Stage” pp.3,Texas
Instrument Application Notes, Texas Instrument Inc., 2010.
[11]KBU8005 thru KBU810 Bridge Recrtifier, Datasheet, Revision:A02, KBU Inc,
[12] NILSSON, J., Electric Circuits , pp. 356, 7th.
[13] SONI, A., ”DC-DC Switching Boost Converter”, ECE 345, 1999.
[14] ROGERS, E., “Understanding Boost Power Stages in Switchmode Power Supplies” pp.1-32, Texas Instrument Application Notes, Texas Instrument Inc.,1999.
[15] MASRI, S., CHAN, P.W.,” Development of a Microcontroller-Based Boost
Converter for Photovoltaic System” EuroJournals Publishing, Inc. 2010
[16] RASHID, M.H., Power Electronic Circuits, Devices and Applications, pp. 77-90, 320-
325, 2nd Edition, Prentice- Hall Inc., New Jersey, USA, 1993
[17] 16f877 Microcontroller Datasheet, Microchip TechnologyInc. 2001
[18] Acs712 Hall Effect Sensor Datasheet, AllegroMicroSystems Inc.,2010
[19] http://www.electronics-tutorials.ws/dccircuits/dcp_9.html
[20] PRESSMAN, A.I., Switching Power Supply Design, pp. 26,2nd,Mcgraw Hills,1998.
8. APPENDICESA. Cost of Project
Equipment Name Number Unit Unit Cost Cost250W Transformer 1 unit 45,00TL 45,00TL
35A Bridge Diode 1 unit 1,80TL 1,80TLMUR3020 Diode 1 unit 4,65TL 4,65TLIRFP260 Mosfet 1 unit 4,00TL 8,00TL2n222 npn transistor 2 unit 0,50TL 1,00TLMAX232 IC 1 unit 0,75TL 0,75TLRS232 Connector 1 unit 0,75TL 0,75TL16f877 Microcontroller 1 unit 12,00TL 12,00TLACS712 Current Sensor 1 unit 15,00TL 15,00TL7805 Voltage Regulator 1 unit 0,75TL 0,75TLLm317T Voltage Regulator 1 unit 0,75TL 0,75TL16 Character Lcd Window 1 unit 13,36 TL 13,36 TLBox of Project 1 unit 20,00TL 20,00TL25A Automaton Fuse 1 unit 30,00TL 30,00TL15 x 15 Pertinax 1 unit 1,40 TL 1,40TL1 unit Charger device TOTAL 155,21TLUpgrading and Extra Euuipment 94,79TLProject Cost 250,00TL
B. Time Table
C. Schematic of Project
D. Codes
#include <16f877.h>#device ADC=10//#define Dout pin_c3
#fuses
XT,NOWDT,NOPROTECT,NOBROWNOUT,NOLVP,NOPUT,NOWRT,NODEBUG,NOCPD
#use delay (clock=4000000)
#use rs232 (baud=2400, xmit=pin_C6, rcv=pin_C7, parity=N, stop=1)
#use fast_io (b)#use fast_io (c)#include <lcd.c>
int duty=1;unsigned long int bilgi1,bilgi2;float deger1,deger2;//unsigned char data=0x00;#int_extvoid ext_charge()
{while(1){
{//output_high(pin_c0);
delay_ms(100); set_adc_channel(1); delay_us(50); bilgi1=read_adc();
set_adc_channel(0); delay_us(50); bilgi2=read_adc(); deger1=((bilgi1*0.004828812)*3); //deger2=((bilgi2*0.004828812)-2.46)*1000/80; lcd_gotoxy(1,1); printf( lcd_putc, "V=%lu ",bilgi1 ); delay_ms(10); lcd_gotoxy(1,2); printf( lcd_putc,"V=%fV I=%dA",deger1,duty); delay_ms(10); delay_ms(1000); if ((bilgi1<833))
{duty=duty+1; set_pwm1_duty(duty); }
else{ duty=duty-1; set_pwm1_duty(duty);//output_low(pin_c0);delay_ms(1000);delay_ms(100);
}}}}void main(){ set_tris_b(0xFF); set_tris_c(0xF0);////////////// set_tris_a(0x0f); //set_tris_c(0x00);/////////////////////// setup_ccp1(CCP_PWM); setup_timer_2(T2_DIV_BY_1,99,1); // Timer2 ayarları yapılıyor set_pwm1_duty(duty); // PWM1 çıkışı görev saykılı belirleniyor setup_adc(adc_clock_div_32); setup_adc_ports(ALL_ANALOG); lcd_init(); enable_interrupts(INT_EXT); enable_interrupts(GLOBAL);
while (1)
{lcd_gotoxy(1,1); printf( lcd_putc, "Tusa bas" ); delay_ms(10); }}
E. Datasheets
