Patent attributes
When impedance calculating conditions are satisfied after a system is started, the impedance of a battery is calculated using the current of the battery, a time variation in open circuit voltage thereof, a time variation in terminal voltage thereof, a time variation in current thereof, and a time variation in impedance thereof. The ratio of the calculated impedance to the initial impedance is calculated. The impedance ratio is subjected to weighting and averaging, thus obtaining a weighted average. When the system is terminated, an impedance-correction-coefficient learned value is updated using the weighted average. Thus, a change in impedance of the battery can be accurately grasped. Advantageously, parameters indicating the state of the battery, e.g., the remaining capacity thereof, reflect the change in impedance, resulting in accurate battery management.
