Patent ID: 7136762

Claim:
A system for calculating the remaining capacity of an energy storage device, the system comprising: voltage detection means for detecting the terminal voltage of the energy storage device; current detection means for detecting the charge and discharge current of the energy storage device; first calculation means for integrating the charge and discharge current detected by the current detection means to calculate a first remaining capacity; second calculation means for estimating the open circuit voltage of the energy storage device on the basis of the terminal voltage detected by the voltage detection means, the charge and discharge current detected by the current detection means and the impedance of the equivalent circuit of the energy storage device calculated in correspondence with the moving average of the current and for calculating a second remaining capacity based on the estimated open circuit voltage; and third calculation means for weighting the first and second remaining capacities with a weight that is set based on the moving average of the current and combining the weighted remaining capacities into the remaining capacity of the energy storage device.