Patent ID: 8432136

Claim:
A battery pack system, comprising: a battery charger comprising a battery charger side connector provided with a first charging current pin, a second charging current pin, a first signal pin, and a second signal pin, the first and second charging current pins for supplying currents, lengths of the first and second signal pins being shorter than lengths of the first and second charging current pins; and a rechargeable battery pack to be recharged by the battery charger comprising; a plurality of rechargeable batteries connected in series or in parallel, a battery pack side connector provided with a first groove for engaging with the first signal pin, a second groove for engaging with the second signal pin, a third groove for engaging with the first charging current pin and supplying the currents to the batteries, a fourth groove for engaging with the second charging current pin and supplying the currents to the batteries, a voltage detector for detecting voltages of the respective rechargeable batteries, a calculator for calculating optimal charging current values based on the voltages of the respective batteries detected by the voltage detector so as to recharge the respective batteries, a communicator for transmitting the optimal charging current values calculated by the calculator to the battery charger, an input circuit in which a battery charger condition signal indicating a condition of the battery charger is input from the battery charger via the first groove and the first signal pin, an output circuit that outputs a battery pack condition signal indicating a condition of the battery pack to the battery charger via the second groove and the second signal pin, and a controller for controlling the voltage detector, the calculator, the communicator, the input circuit, and the output circuit, wherein the battery charger comprises a current controller that supplies the currents according to the optimal charging current values from the battery pack to the batteries in the battery pack, and when engaging of the first groove and the first signal pin and engaging of the second groove and the second signal pin are canceled, the current controller stops supply of the currents.