A battery charger, or recharger, is a device used to put energy into a secondary cell or rechargeable battery by forcing an electric current through it. The charging protocol depends on the battery’s size and type. Some battery types have a high tolerance for overcharging and can be recharged by connection to a constant voltage source or a constant current source; simple chargers of this type require manual disconnection at the end of the charge cycle or may have a timer to cut off charging current at a fixed time.
Other battery types cannot withstand long high-rate over-charging; the charger may have temperature or voltage sensing circuits and a microprocessor controller to adjust the charging current, determine the state of charge, and cut off at the end of the mission.
There are two types of electric car chargers:
On-board charger: the charger is located and installed in the car
Off-board charger: the charger is not found or not installed in the vehicle.