A method and apparatus for determining a state of health of a battery are disclosed. The apparatus comprises means for sensing a voltage of the battery, means for sensing a current through the battery, means for estimating a value of an equivalent circuit model parameter of the battery from the sensed voltage and current, wherein the equivalent circuit model parameter is based at least in part on an internal capacitance of the battery, means for storing a predetermined relationship between the equivalent circuit model parameter and the battery state of health, and means for calculating a state of health of the battery based on the estimated value of the equivalent circuit model parameter using the predetermined relationship.