A device for restoring the charge of a battery. It consists, essentially, of a mains transformer to reduce household mains current (in Britain, 240 volts AC) to 12 volts DC. A built-in rectifier changes the alternating current to direct current. As a rule, a domestic battery charger has an output of about 2 amps although they can be obtained to charge as high as 6 amps. The more sophisticated models have an ammeter built in to check the charging rate and an automatic limiter which reduces the output as the battery charge rises (6-volt chargers are also available).
Also see: How it Works - The Battery