The Design And Construction Of Auto Cut-off Car Battery Charger

Electrical/electronic Engineering Project Topics

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This project which comprise of many chapters that deals extensively with designs and construction of battery charger with auto-cut off which is capable of charging a 12 volts battery. In this construction research, designs was carried out which historic research was used to break down and evaluate to a low level understating of what an auto-cut of charger system is all and how it can be constructed and the main purpose of the project. The charging current as well as the power to the circuit is obtained from 1 0 – 18 volts 2 Ampere step down transformer. The law voltage AC can be rectified by the bridge rectifier comprising D1 through D4 and made ripple free by the smoothing capacitor C1 for charging purpose, 18V DC is used while to power the circuit, 9 volts regulated DC form IC1 is used. IC2 (CA 3140) is used as a simple voltage comparator drive the relay. After the series steps of inversion pure DC is achieved that can charge a specified DC battery. The relay saves as the Tripping command to the pin i.e to operate automatically when the battery is fully charged and when is weak.


Title page                                                                         i

Approval page                                                                 ii

Certification                                                                    iii

Dedication                                                                       iv

Acknowledgement                                                           v

Abstract                                                                          vi

Table of contents                                                             vii

List of tables                                                                    xii

List of figures                                                                  xiii


1.0     INTRODUCTION                                             1

1.1      Background of the Study                                        1

1.2      Charging Formation                                               1

1.3      Types of Batteries                                                   3

1.4      Primary (Dry Cell)                                                   3

1.5      Secondary (Wet Cell)                                               4

1.6      Aims and Objective                                                 6

1.7      Scope of the Study                                                  6

1.8      Report Organization                                               7

CHAPTER TWO                                      

2.0      LITERATURE REVIEW                                   9

2.1      Definition of Important Terms                                12

2.1.0                Transformer                                                    12

2.1.1        AC TO DC Converter (Rectifier Circuit/Unit)     14

2.1.2        Filtering Unit                                                      17

2.1.3        Voltage Regulation                                              19

2.1.4        Comparator                                                        21

2.1.5        Thyristor                                                             22

2.1.6        Resistor                                                               23

2.1.7        Diode                                                                   24

2.1.8        Relay                                                                   24

2.1.9        Zener Diode                                                         25

2.1.10    Light Emitting Diode (LED)                                25



3.1      Design Methodology                                                26

3.1.1        Up-Down Design                                                 27

3.1.2        Down-Up Design                                                 27

3.2      The Mains Unit                                                       28

3.3      The Power Supply Unit                                           29

3.3.1        Transformer                                                        31

3.3.2        Rectifiers                                                             33

3.3.3Filters                                                              34

3.3.4        Voltage Regulator                                               35

3.4      The Charging Unit                                                  36

3.5      Voltage Comparator Unit                                       37

3.6      Over-charge cut Unit                                              38

3.7      Component Description                                          38

3.7.1        Resistors                                                             38

3.7.2Capacitors                                                       42

3.7.3        Transistors                                                          44  Transistor Currents                                            48

3.7.4        Relay                                                                   53

3.8      System Specification                                               53



4.1      Construction                                                           55

4.0.1                Component Soldering and Arrangement Used

 in the Circuit Diagram                                  55

4.0.2                Construction of Casing                                   55

4.0.3                Packaging of Components in the Casing        56

4.0.4                Assembling of Section                                     56

4.2      Testing of the Project                                              57

4.3      Battery Condition Test                                           58

4.4.1                Sensing and Switching Circuit                       59





AND EVALUATION                                         62



6.1      Conclusion                                                              65

6.2      Recommendation                                                    67

6.3      Summary                                                                67

References                                                               68



Table 3.1:Tables of values of resistor colour codes  40



Fig 3.2: Block diagram of power supply unit                 31

Fig 3.3 Transformer and its output                                32

Fig 3.4: Circuit Diagram of a full wave rectifier             33

Fig 3.6: Symbol of 7805 Regulator                         35


Fig 3.7:    Voltage Regulator and output wave form of

a regulated voltage                                                              36

Fig 3.8     Diagram of MOSFET                                       37

Figure 3.10      Circuit and schematic diagram of

a polarized capacitor                              43

Fig 3.11   Circuit and schematic diagram of

non-polar capacitor                                        44

Fig 3.12 Current path of a Transistor                            49

Fig 3.13   Model of NPN Transistor                                 50

Fig 3.14 symbol of n-p-n and p-n-p transistor               52

Fig 4.1     Circuit Diagram of Auto Cut-Off Car

Battery Charger                                              61



7.1     Background of the Study

In the context of renewable energy source, a device which consists of electrodes and electrolytes for the storage of chemical energy, but brings about a reaction between it’s electrodes and the electrolyte in a ways to cause the flow of electrons through an external circuit is known as a battery the circuitory to recharge the batteries in a portable product is an important part of any power supply design. The complexity and cost of the charging system

 primarily depends on the type of battery and the recharge time.

7.2     Charging Formation

In the realm of battery charging, charging methods are usually separated into two general categories.

Fast charging: is typically a system that can recharge a battery in about one or two hours.

Slow charging: This is usually refer to an overnight recharge, i.e it is usually defined as a charging current that can be applied to the battery indefinitely without damaging the cell. (This method is sometimes referred to as a trickle charging).

The maximum rate of trickle charging which is safe for a given cell type if dependent on both the battery chemistry and the cell construction when the cell is fully charged, continued charging causes gas to form within the cell. All of the gas formed must be able to recombine internally, or pressure will build up within the cell eventually leading to gas release through opening of the internal vent (which reduces the life span of the cell).

This means that the maximum safe trickle charge rate is highly dependent on battery chemistry, but also on the construction of the internal electrodes.


7.3     Types of Batteries

7.4     Primary (Dry Cell): are those whose electrolyte dries up when used to it’s ampere – hour rating and cannot be recharge. Dry cell batteries are different from wet cells because their electrolytes are contained in a low-moisture paste. Regardless of their sizes, they have the same basic components. At the center of each is a Rod called the cathode which is often made up of carbon and surrounded by an electrolyte paste. Different chemicals can be used to create this paste such as ammonium chloride and managanese dioxide, depending on the type of battery. The cathode and electrolyte paste are wrapped in paper or cardboard and sealed into a metal cylinder called an anode which is typically made of zinc.

7.5     Secondary (Wet Cell): It is the type of whose chemical energy can restored through a charging process. Although there are different types of secondary battery which comprises lead acid, nickel-cadmium, and silver zinc battery.

A wet cell is a type that operates by liquid electrolytic solution, it often runs down move quickly in a hot climate because the heat causes the plates to either from the electrolyte solution.

Furthermore, a battery is a combination of cell connected together and a cells is of importance partially where maximum performance and life are obtained. As long as a battery is in use, it stores chemical energy which is being converted to electrical energy falls. This falls in chemical energy leads to a corresponding fall in terminal voltage.

A constant potential method of charging is adopted in this project work it is a phenomenon whereby the alternating voltage from the main is converted to direct voltage through rectification.

The direct current from the rectifier is then passed through the battery that is being charged in the  reversed direction in which the battery supplies current to the external circuit. The charger is intended to charge batteries with terminal voltage up to 12 volts. In incorporates a sensing technique to monitor when the battery has been charged to its rated terminal voltage so as to automatically cut off supply to the battery.

Centuries ago the use of tricycle was established with the help of coal engienes or horses to ride on the same paved horizon. Before the charger circuits with nIcke-cadmium, Nickel metal hydride, and lithium-ion batteries. Which can be charged and can retain charged particles inside until it is used up with it’s connected circuit for operation.


7.6     Aims and Objective

The main purpose of this project work is the major of constructing a system that has the ability measures of recharging a battery when it runs down. The design conforms an auto charging cut off circuit that operates when the battery is fully charged.


7.7     Scope of the Study

The battery charger is a device that is well design to perform the function of converting 50Hz or 60Hz Ac into an equivalent variable DC output. The DC produced after the rectification process is then applied directly in charging of our batteries. The battery charger can perform the function of charging 12V battery, 24 volt battery depending on the desired specification of construction.

This project design function basically to recharge batteries not exceeding 36 volts and a line up of batteries not exceeding ten in numbers. The current supply of the charging system does not exceed 3amp per charging ratio of line.


7.8     Report Organization

Six chapters were converted in the course of design and development of this project. The chapters and their contents are as follows:

Chapter one is the introductory chapter that gives the aims, scope and limitation of the project.

Chapter two is the literature review, it deliberates on different related works done by several authors with dates. It also discusses on the limitations of some of these works

Chapter three discusses the design methodology of the project. Also discussed, is the requirement analysis which is all the information, gathered from a wide research on battery charger system.

Chapter four deals with the system testing and evaluation also how the components were tested.

Chapter five is the Bill of Engineering measurement and Evaluation (BEME) i.e the component last unit and Evaluation.

Chapter six is the summary, conclusion and recommendation. The contribution of the project, achievements and problems for further enhancement, and reference discussed in this chapter.

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The Design And Construction Of Auto Cut-off Car Battery Charger