Patent ID: 7531986

Claim:
An auxiliary power supply for use with a battery powered device including first electrical circuitry which presents a time varying electrical load and a first rechargeable battery which provides electrical energy to the first electrical circuitry, the auxiliary power supply comprising: a battery receiving region adapted to receive a second battery; second electrical circuitry, wherein the second electrical circuitry receives a signal from the battery powered device, which signal is indicative of the magnitude of the time varying electrical load, wherein the second electrical circuitry utilizes energy from the second battery to produce a power supply output ( 110 p , 110 n ) for recharging the first rechargeable battery and for providing electrical energy to the first electrical circuitry, and wherein the second electrical circuitry adjusts the power supply output as a function of the charge state of the first rechargeable battery, the charge state of the second battery, and the signal; a first electrical connector in operative communication with the second electrical circuitry and adapted to selectively electrically connect the power supply output to the battery powered device: wherein the signal includes a measured value of the time varying electrical load and wherein the measured value of the time varying electrical load includes a measured value of an electrical load current, and wherein the second electrical circuitry adjusts the power supply output current as a function of the first rechargeable battery voltage, the second battery voltage, and the measured value of the time varying electrical load current.