Abstract: A self contained battery charger is disclosed for use in charging an external battery through a pair of connecting cables. The battery charger comprises an internal battery for providing a first predetermined battery voltage and a DC to DC converter, connected to the internal battery, for converting the first predetermined voltage to a low current signal. First switching circuitry is provided for communicating a low current signal to the external battery. Status monitoring circuitry is provided for monitoring voltage and/or current conditions when said low current signal is communicated to the external battery. Second switching circuitry is provided for communicating a high current signal to the external battery in response to sensed voltage and/or current conditions.