A charging system includes a charger operable for providing a charging current to a battery pack. The charger includes a charging switch coupled between a power source and the battery pack, and a controller operable for controlling the charging switch. The controller includes a voltage sensing pin coupled to the battery pack. The controller is operable for measuring a battery voltage of the battery pack via the voltage sensing pin during a plurality of discrete time slots, and is operable for adjusting a length of a time interval between two consecutive time slots of the plurality of discrete time slots based on the battery voltage, and the controller is operable for determining an identity of the battery pack and configuring charging parameters according to the identity.