Patent ID: 7902828
Filing Date: 2011-03-08
Classification: G01R

Abstract:
1. A method of monitoring the electric power of a battery by measuring an internal resistance of the battery, comprising the steps of: (1) coupling a first power transistor across the two terminals of the battery to provide a first known external load, so as to draw a first transient current for a very transient sampling time, while measuring the voltage across the battery, thus obtaining a reference voltage; (2) coupling a second power transistor across the two terminals of the battery to provide a second known external load, so as to draw a second transient current for a very transient sampling time while the first load is still coupled across the two terminals of the battery, and while measuring the voltage across the battery, thus obtaining a load voltage, and measuring the second transient current; and (3) calculating the internal resistance of the battery by subtracting the load voltage from the reference voltage and dividing by the second transient current.