Abstract: Terminal plates, connected to the opposite terminals of a direct current (DC) source, are mounted and/or formed to be engageable with the terminals of the operating batteries in a battery operated device. Two terminal plates are mounted on disc shaped insulation pieces or are formed into conducting discs to match the conventional battery shape. These terminal discs are inserted into the battery compartment at opposite ends of the normal batteries in series and with like polarities matching. Selection of the position of an insulating pad or disc surface results in the external source acting as a substitute power supply or as a charging source for rechargeable cells. In a special form, the terminal plates are mounted on opposite sides of a single insulation disc, connected to the DC source, and the disc inserted between tandem cells or between the end cell and compartment contactor to provide operating energy to the device.