Abstract: A holster for a handheld, power intensive electronic device, such as a cellular telephone, incorporates within it a supplemental battery pack. The supplemental battery pack is used to recharge or maintain main, onboard battery pack of the cellular telephone and also to power certain supplemental circuits. The use of the docking-holster at least doubles the useful life of the device battery, which may be kept conveniently small.

Abstract: A self-contained, rechargeable battery pack uses a coulomb-counting control circuit to measure charge received by and taken from the cells and to store a current charge status of those cells. The control circuit controls a charge/discharge pass transistor in the pack to provide overcharge protection. An always-on trickle charge resistor insures that the controller is in operation during charging even when the cells associated with the controller are completely discharged. A Schottky diode is placed across the charge/discharge pass transistor in order to minimize the discharge dropoff voltage between the terminal of the cell and a corresponding external terminal. The present invention considerably lengthens the useful life of nickel-based rechargeable batteries, as measured in terms of both the number of cycles and the available capacity per cycle, while requiring no extra terminals.