A bidirectional battery charge control system for a portable electronic device which uses a rechargeable main battery. The system enables the connection of an auxiliary battery to the device for inputting additional current to the device. Control of the current flow into and out of the auxiliary battery is performed by a bidirectional charger. The auxiliary battery can contain one or more readilyavailable primary or secondary cells, and the bidirectional charger is such that an external charger connected to the device, generally used to charge the main rechargeable battery of the device, canalso recharge a secondary cell or cells in the auxiliary battery, if such are installed. The use of such an auxiliary battery enables the main battery to be hard-wired into the device.