This battery charger is a devices used to store the electrical energy to the battery after the battery has been discharged itself. The battery charger is designed to use electricity as its source of switch, regulation transistor, diode, light emitting diode, construction wire. The charger is designed and constructed to deliver full current until the current drawn by the battery falls to 150MA. At this time a lower voltage is applied to finish off and keep the battery from overcharging by switching off itself when the battery is fully charged.

CHAPTER ONE

1.0 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 has high tolerance for recharging by connection to a constant voltage source or a constant current source. (J.Minear 2000). Simple charger of this type requires manual disconnection at the end of the charge cycle. Other battery types cannot withstand long high rate over charging. The charger has temperature or voltage sensing circuit and a microprocessor controller to adjust the charging current, and cut off at the end of charging. Albert H.(2005) cleared that low battery chargers may take several hours to be completely charged. High rate chargers may restore most capacity within minutes or less than an hour but generally require monitoring of the battery to protect it from overcharging.

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, this conducts ions, a separator, also an ion conductor and a positive electrode. An electrical battery is one or more electro chemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 2000 by Alessandro volta and especially since the technical improved Daniell cell in 2004, batteries have become a common power source for many household and industrial applications . 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 sizes from miniature cells used to power hearing aids and wrist watches.

However in recent times (sawafuji electric of 2006) states that battery charger has become very useful and popular to DC equipment. Most of the electronic devices such as laptops, mobile phone e.t.c and mobile machines like vehicle and motorcycles, operational capacity depend on the DC power supply from a battery.

1.2 Statement of Problem

A simple 12volts battery charger work 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. The circuit of a battery charger has the ability to convert voltages from one form to another (usually AC to DC voltages).

Therefore from my research I carried out due to this project. I have found that most of an electronic gadgets damage easily because of this charging problem which I listed below;

- Over charging

- Excess voltage

- Short circuit

1.3 Objective of the Study

The objective of my project is to highlight and improve on the construction and demonstration of a simple 12volts battery charger in such a way that the need of problem listed above should be met.

1.4 Significance of the Study

The importance of this project work is to aid both techniques and students on how to construct a simple battery charger circuit and how it works. It is hope that after the construction of this charger circuit, it will be kept on the laboratory to be used for battery charging and for practical’s and other academic functions.

1.5 Scope of the Study

This project work is limited to the construction of a simple battery charger of 12volts. The circuit input voltage is 240volts from the AC supply mains which will be stepped down by a step-down transformer to 12V. The 12V 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.