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MAIN OPERATED BATTERY CHARGERS

A battery charger is an electrical device that is used for putting energy into a battery. The battery charger changes the AC from the power line into DC suitable for charger. However, DC generator and alternators are also used as charging sources for secondary batteries. In general, a mains-operated battery charger consists of the following elements:

1. A step-down transformer for reducing the high AC mains voltage to a low AC voltage.

2. A half-wave or full-wave rectifier for converting alternating current into direct current.

3. A charger-current limiting element for preventing the flow of excessive charging current into the battery under charge.

4. A device for preventing the reversal of current i.e. discharging of the battery through the charging source when the source voltage happens to fall below the battery voltage.


In addition to the above, a battery charger may also have circuitry to monitor the battery voltage and automatically adjust the charging current. It may also terminate the charging process when the battery becomes fully charged. However, in many cases, the charging process is not totally terminated but only the charging rate is reduced so as to keep the battery on trickle charging. These requirements have been illustrated in Figure.

Most of the modern battery chargers are fully protected against the following eventualities:

(a) They are able to operate into short-circuit.
(b) They are not damaged by a reverse-connected battery.
(c) They are operated into a totally flat battery.
(d) They can be regulated both for current and voltage.

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