Design And Construction Of Battery Charger

1.1 INTRODUCTION
A device, which consist of electrodes and electrolyte for the storage of chemical energy, but brings about a reaction between its electrodes and the electrolyte in a way to cause the flow of electrons through an external circuit is known as a battery.
There are two types of batteries, these include the primary and secondary battery. The primary (dry cell) is one whose electrolyte dries up when used to its ampere-hour rating and cannot be recharged while the secondary (wet cell) is one whose chemical energy can be restored through a charging process. There are different types of secondary battery. These comprises lead acid, Nickel-cadmium and silver zinc battery.
Furthermore, a battery is a combination of cells connected together and a cell is a simple source of electric potential. The maintenance of secondary battery is of importance partially where maximum performance and life are obtained. As long as a battery is in use, its stored chemical energy, which is being converted to electrical energy falls. This falls in chemical energy leads to a corresponding fall in its 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 12volts. It 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.
Hence, a battery charger which is of low cost, highly efficient and cheap to maintain is needed to restore its rated terminal voltage.
The entire circuit is made up of five basic units and details of each units is highlighted in the subsequent chapters.