Patent ID: 8847554

Claim:
A battery management system for managing the voltage of a battery cell providing power to a load, the battery management system to prevent the battery cell from being drained to a deep discharge condition after the battery management system has turned off power from the battery cell to the load, the battery management system comprising: a semiconductor switch coupled parallel to the battery cell, wherein the semiconductor switch is in an on condition when the voltage across the battery cell exceeds a first threshold voltage and in an off condition when the voltage across the battery cell is below a second, lower, threshold value; and a microprocessor coupled to the semiconductor switch via a battery voltage sensing input; wherein the semiconductor switch comprises first and second complementary transistors and a Zener diode; and wherein the microprocessor monitors the voltage across the battery cell when the semiconductor switch is on, and turns itself off in response to the battery voltage sensing input falling to zero when the monitored voltage is less than the second threshold voltage, thereby preventing further current drain from the battery cell.