DESIGN AND CONSTRUCTION OF BATTERY CHARGER

CHAPTER ONE

INTRODUCTION

1.1 Background of the study

A battery charger is a device used to introduce energy into a secondary cell or rechargeable battery by forcing an electric current through it. The charging protocol depends on the size and type of the battery being charged. Some battery have high tolerance for recharged by connection to a constant voltage source or a constant current source; simple chargers of this type require manual disconnection at the end of the charge cycle, or may have a timer to cut off charging current at a fixed time. Other battery types cannot withstand long highrate overcharging, the charger may have temperature or voltage sensing circuits and a microprocessor controller to adjust the charging current, and cut off at the end of charge.

A tackle charger provides a relatively small amount of current, only enough to counteract selfdischarge of a battery that is idle for a long time. Slow battery chargers may take several hours to complete a charge, highrate chargers may restore most capacity within minutes or less than an hour, but generally require monitoring of the battery to protect it from overcharge Emerson, 1998.

A battery, which is actually an electric cell, is a device that produces electricity from a chemical reaction. In one cell battery, a negative electrode; an electrolyte, which conducts ions; a separator, also an ion conductor; and a positive electrode. an electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technical improved Daniell Cell in 1936, batteries have become a common power source for many household and industrial applications Emerson 1998.

There are two types of batteries: Primary Batteries disposable batteries, which are designed to be used once and discarded, and Secondary Batteries rechargeable batteries, which are designed to be recharged and used multiple times. Battery comes in many size, from miniature cells used to power hearing aids and wristwatches to battery banks the size of rooms that provide standby power for telephone exchanges and computer data centers and inverters.

However, in recent times, battery charger has become very useful and popular to DC equipment. Most of the electronic devices such as laptops, mobile phone, etc., and mobile machines like vehicle and motorcycles operational capacity depend on the DC power supply from a battery.

1.2 Scope of the study

This project work is limited to the construction and demonstration of a simple battery charger of 12volts. The circuit input voltage is 240volts from the A.C supply mains which will be stepped down by a stepdown transformer to 12volts. The 12volts A.C is rectified through a bridge rectifier and filtered through capacitor connected in parallel from the positive terminal of the bridge rectifier. The output voltage is used to charge a battery.

1.3 Statement of the problem

A simple 12volts charger works by supplying a constant DC or pulsed DC power source to a battery being charged. The simple charger does not alter its output based on time or the charge on the battery. This simplicity means that a simple charger is inexpensive. The circuit of a battery charger has the ability to convert voltages from one form to another usually AC to DC voltages. This process is carried out through the use of some important components like: rectifiers, capacitor to filter and remove ripples from the AC source and a voltage regulator IC. However, this project is based on the construction of a 12volts simple battery charger with local materials to reduce cost.

1.4 Purpose of the study

The purpose of this project work is to design construct and demonstrate how a simple 12volts battery charger works.

1.5 Significance of the study

A simple 12 volt battery charger is a simple circuit that comprises of different component that are soldered together on a circuit board to give or produce a require function. Therefore, the importance of this project work is to aid both technicians and students on how to construct a simple battery charger circuit and how it works.it is hoped that after the construction of this charger circuit, it will be kept on the laboratory to be used for battery charging and for practicals and other academic functions.

1.6 Limitation

During the project work, the researcher encountered the following problems which in one way or the other have prevented him from completing the work at the usually time. These include: financial problems, time factor and unavailability of material which the researcher have to move from far distance area in search of textbooks and other important materials.