This battery charger provides a maximum 4 Amp charge and it is double insulated. It features reverse polarity and thermal overload protection. A battery charger, recharger, or simply charger, is a device that stores energy in a battery by running an electric current through it. The charging protocol (how much voltage or current for how long, and what to do when charging is complete) depends on the size and type of the battery being charged. A main operated battery charger that is compact in design. It is made for charging 12V batteries in cars, motorcycles and lawnmowers.