Patent ID: 7443139

Claim:
A battery state-of-charge estimator comprising: a voltage detector unit which detects a voltage of a battery; an internal resistance estimator unit which estimates an internal resistance of the battery; an estimated charging/discharging current calculator unit which calculates an estimated charging/discharging current of the battery based on the internal resistance of the battery determined by the internal resistance estimator unit, the voltage of the battery, and an open voltage of the battery; an SOC estimator unit which estimates a state of charge SOC of the battery based on the estimated charging/discharging current determined by the estimated charging/discharging current calculator unit; an open voltage calculator unit which sets the detected voltage of the battery as the open voltage of the battery at an initial calculation of the charging/discharging current and, after the initial calculation, calculates the open voltage of the battery based on the SOC which is previously estimated, and a current detection abnormality detector unit which compares the measured charging/discharging current value which is detected by the current detector which detects the charging/discharging current of the battery and the estimated charging/discharging current value which is determined by one of the estimated charging/discharging current calculator unit, the first charging/discharging current calculator unit, and the second charging/discharging current calculator unit, and determines that the current detector unit is abnormal when a difference between the current values is greater than a predetermined difference and that the current detector unit is normal when the difference is a predetermined value or smaller, wherein the estimated charging/discharging current calculator unit, a first charging/discharging current calculator unit, or a second charging/discharging current calculator unit calculates the estimated charging/discharging current of the battery based on the internal resistance of the battery, the voltage of the battery, the open voltage of the battery, and a polarization voltage, and wherein the SOC is estimated based on the estimated charging/discharging current value when the current detection abnormality detector unit determines that the current detector unit is abnormal and the SOC is estimated using the measured charging/discharging current value when the current detection abnormality detector unit determines that the current detector unit is normal.