Patent ID: 8278876

Claim:
An apparatus comprising: a battery pack comprising: at least one battery cell; a first and a second voltage terminal coupled to said at least one battery cell, said first and said second voltage terminals configured to be removably coupled to a load; a switch disposed between said at least one battery cell and at least one of said first and said second voltage terminals, said switch having an ON resistance dependent on a temperature of said switch; a thermistor located proximate said switch, said thermistor having a resistance varying with changes in said temperature, wherein said thermistor is configured to sense said temperature of said switch and to output a signal representative of said temperature of said switch; and battery state monitoring circuitry configured to determine a current flowing to or from said at least one battery cell based on a voltage drop across said switch caused by a current flowing through said switch and said signal from said thermistor representative of said temperature of said switch.