Patent ID: 8274395

Claim:
A power supply system, comprising: a first battery terminal; a second battery terminal; a third battery terminal; a fourth battery terminal; a first battery coupled to the third and fourth battery terminals; a battery sensing element coupled to the first and second battery terminals and configured to sense whether a second battery is between the first and second battery terminals based on a voltage across the first and second battery terminals, the battery sensing element further configured to transmit an alarm signal when the voltage falls below a first threshold; a diode coupled to the second battery terminal; and a current control element coupled to the diode and the first and second battery terminals, the current control element configured to sense a voltage across the first and second battery terminals and to selectively transfer charge across the diode based on the voltage sensed by the current control element such that leakage current passing through the diode from the first battery is prevented by the current control element from causing the battery sensing element to falsely sense a battery between the first and second terminals.