Design And Construction Of A Battery Charger With Over-Charge Cut-Off

1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDY
A battery charger is described as is a device that provides electricity to convert into stored chemical energy for storage in an electrochemical cell by running an electric current through it. [Zhang et al, 2013].
A battery charger consists of a rectifier circuit, power circuit, ripple monitoring, control circuit, regulator circuit.
A Battery charger comes in various designs and voltage. The choice of a particular charger depends largely on the size of battery. Mini battery charger could be used to charge batteries whose voltage is 12 volts.
The battery charge is built in such a way that it delivers a constant value of d.c current into the battery it is charging in the opposite direction from which current flows on the batteries during discharge one cannot successfully design a battery charge without a fundamental understanding of the accumulator because it also makes up the operation according to [Zhang et al, 2013].
This work is aimed at building an automatic battery charger which comprises of overcharge cut – off feature.

1.1 Problem Statement
There is nothing that is as frustrating and dangerous as when a battery is plugged and at the end it was discovered that the battery did not charge. And nothing is as dangerous as when a battery was fully charged and the owner is not aware of the charging state. This study solve problems such as not knowing when a battery is charging and when it is fully charged which can cause the battery not to charged or to over-charge.
The battery charge is built in such a way that it delivers a constant value of d.c current into the battery it is charging in the opposite direction from which current flows on the batteries during discharge one cannot successfully design a battery charge without a fundamental understanding of the accumulator because it also makes up the operation.

1.2 Aim and Objective of Study
The main aim of this work is to build an automatic battery charger which comprises of indicators that indicates charging process and charging level indicator. The objectives are:
i. To build the device
ii. To know when a battery is charging or not
iii. To know the status of a battery thereby saving the battery from over-charge

1.3 Significance of Study
Carrying this work will go along way teaching students how battery charger is been made and the operation of battery charger. This study will also be of great benefit to all users of charger and rechargeable devices in that it will help them to understand how their battery is been charged and how chargers are operated.

1.4 Scope of Study
The scope of this work focuses on the building of a 12v battery that incorporated overcharge cut-off relay. In this work, a voltage sensor circuit is incorporated to sense the voltage of the battery under charge. The charger has the ability to automatically switch OFF when the battery voltage reaches the required optimum level with the help of the contact relay, the transistor and the zener diode.

1.5 Limitations of Study
This charger can only be used for 12v batteries. The final packaging of the device will compose of two LEDs which includes LED for power, and overcharge cut-off LED.

1.6 Definitions of terms
Below are terms that are frequently used in this work and their definitions:
Battery: a container consisting of one or more cells, in which chemical energy is converted into electricity and used as a source of power.
Charger: a device for charging a battery or battery-powered equipment.
Capacitor – a charge storage device made up of two metallic plates separated by a dielectric, with equal but opposite charges. The AC impedance of a Capacitor is (1 / jWL) and acts as an open circuit in DC applications.
Circuit – a complete path that allows electrical current from one terminal of a voltage source to the other terminal.
Alternating (AC) Current – currents that have a harmonic time dependence.
Ampere (A) – the unit of measurement for electrical current in coulombs per second.