A Pulse Width Modulation Of Simple And High Performance Battery Balancing System

 ABSTRACT

For balancing battery cells connected in a series string, a simple and high performance battery balancing system is proposed. In this system, a technique of DC to DC converter with PWM control is used for balancing all cell voltages completely. The switching surge and noise are made small by soft switching with inductor commutation. This system is suitable for electric vehicles, hand-held personal computers, UPS etc.

 ABBREVIATIONS OR GLOSSARY:

C         Battery Capacity, in ampere-hours [Ah]

DTSC Double-Tiered Switched Capacitor balancing

EV      Electric Vehicle

EPNGV Extended Partnership for a New Generation of Vehicles

HEV  Hybrid Electric Vehicle

ICE    Individual Cell Equalizer

Li-ion Lithium-Ion

Li-Po        Lithium-Polymer

MSC  Modularized Switched Capacitor balancing

MSI   Multi-Switched Inductor balancing

MpT Multiple Transformer balancing

MWT Multi-Winding Transformer balancing

PWM Pulse Width Modulation

SC      Switched Capacitor balancing

SoC   State of charge [%]

SoH   State of Health [%]

SR      Switched Resistor balancing

SSC    Single Switched Capacitor balancing

SSI     Single Switched Inductor balancing

ST      Shared Transformer balancing

SWT Single Winding Transformer balancing

 TABLE OF CONTENT

COVER PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

TABLE OF CONTENT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE PROJECT
• OBJECTIVE OF THE PROJECT
• PURPOSE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• SCOPE OF THE PROJECT
• APPLICATION OF THE PROJECT
• PROJECT WORK ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

2.1      REVIEW OF DIFFERENT TYPES OF INTRUDER SENSOR

CHAPTER THREE

DESIGN METHODOLOGY

3.1      SYSTEM BLOCK DIAGRAM

3.2      DESCRIPTION OF BLOCK

3.3      SYSTEM CIRCUIT

3.4      SYSTEM OPERATION

CHAPTER FOUR

RESULT ANALYSIS

• INSTALLATION OF THE COMPLETE DESIGN
• CONSTRUCTION PROCEDURE AND TESTING
• CASING AND PACKAGING
• ASSEMBLING OF SECTIONS
• TESTING OF SYSTEM OPERATION
• PROBLEM ENCOUNTERED
• COST ANALYSIS

CHAPTER FIVE

5.1 CONCLUSION

5.2      RECOMMENDATION

PREFERENCES

 CHAPTER ONE

1.0                                                      INTRODUCTION

Charging a battery with a solar system is a unique and difficult challenge. In the “old days,” simple on-off regulators were used to limit battery outgassing when a solar panel produced excess energy. However, as solar systems matured it became clear how much these simple devices interfered with the charging process.

The history for on-off regulators has been early battery failures, increasing load disconnects, and growing user dissatisfaction. PWM has recently surfaced as the first significant advance in solar battery charging.

PWM solar chargers use technology similar to other modern high quality battery chargers. When a battery voltage reaches the regulation setpoint, the PWM algorithm slowly reduces the charging current to avoid heating and gassing of the battery, yet the charging continues to return the maximum amount of energy to the battery  in the shortest time. The result is a higher charging efficiency, rapid recharging, and a healthy battery at full capacity.

In addition, this new method of solar battery charging promises some very interesting and unique benefits from the PWM pulsing. These include:

1. Ability to recover lost battery capacity and desulfate a
2. Dramatically increase the charge acceptance of the

1.1                                       BACKGROUND OF THE STUDY

Battery management system (BMS) is an important part of the electric vehicle (EV). It protects the battery system from damage, predicts and increases battery life, and maintains the battery system in an accurate and reliable operational condition. The BMS performs several tasks such as measuring the system voltage, current and temperature, the cells’ state of charge (SoC), state of health (SoH), and remaining useful life (RUL) determination, protecting the cells, thermal management, controlling the charge/discharge procedure, data acquisition, communication with on- board and off-board modules, monitoring, storing historical data and – most importantly – cell balancing.

Imbalance of cells in battery systems is an essential factor in the battery system life. Without the balancing system, the individual cell voltages will drift apart over time. The capacity of the total pack will also decrease more quickly during operation and the battery system will fail prematurely [1]. Quite a lot of cell balancing/equalization methods have been proposed such [1-35] and reviewed in [1-6].

The cells imbalance is caused by internal and external sources according to [35]. Internal sources include manufacturing variance in charge storage volume, variations in internal impedance and differences in self-discharge rate. External sources are mainly caused by some multi-rank pack protection ICs, which drain charge unequally from the different series ranks in the pack. In addition the thermal difference across the pack results in different self discharge rates of the cells.

The balancing topologies can categories as passive and active balancing as shown in Fig. 1. The passive balancing methods removing the excess charge from the fully charged cell(s) through passive, resistor, element until the charge matches those of the lower cells in the pack or charge reference. The resistor element will be either in fixed mode as [6-7] or switched according the system as [1-6], [8-10].

1.2                                           OBJECTIVE OF THE STUDY

Battery systems are affected by many factors, a key one being the cells unbalancing. Without the balancing system, the individual cell voltages will differ over time, battery pack capacity will decrease quickly. That will result in the failure of the total battery system. The objective of the study is to discuss and correct the unbalancing system of batteries using pulse width modulation.

1.3                                       SIGNIFICANCE OF THE STUDY

The benefits noted above are technology driven. The more important the PWM technology on battery charing system. These advantages are as below:

•       Longer battery life:

• reducing the costs of the solar system
• reducing battery disposal problems

•       More battery reserve capacity:

• increasing the reliability of the solar system
• reducing load disconnects
• opportunity to reduce battery size to lower the system cost

•       Greater use of the solar array energy:

• get 20% to 30% more energy from your solar panels for charging
• stop wasting the solar energy when the battery is only 50% charged
• opportunity to reduce the size of the solar array to save costs

the PWM constant voltage series charge controller will provide the recharging current according to what the battery needs and takes from the controller. This is in contrast to simple on-off regulators that impose an external control of the recharging process which is generally not responsive to the battery’s particular needs.

The PWM controller put 20% to 30% more of the energy generated by the solar array into the battery than the on-off regulator.

1.4                                            PROBLEM OF THE STUDY

As batteries cycle and get older, they become more resistant to recharging. This is primarily due to the sulfate crystals that make the plates less conductive and slow the electro-chemical conversion.

The PWM constant voltage charging will always adjust in regulation to the battery’s needs. The battery will optimize the current tapering according to its internal resistance, recharging needs, and age. The only problem with PWM charging is that gassing may begin earlier.

1.5                       DEFINITION OF PULSE WIDTH MODULATION

Pulse Width Modulation (PWM) is the most effective means to achieve constant voltage battery charging by switching the solar system controller’s power devices. When in PWM regulation, the current from the solar array tapers according to the battery’s  condition and recharging needs.