Abstract: A method and an apparatus for computing a charging state of a battery without being affected by an influence of polarization are provided. First computing means computes a voltage-current characteristic including the influence of the polarization during an decrease of a discharge current of the battery on the basis of a terminal voltage and discharge current measured while the battery carries out a constant load discharge with a current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge. A second computing means shifts the voltage-current characteristic to a specific extent in the direction of a voltage coordinate axis. A residual voltage drop value in advance stored by storing means is added to a present estimated voltage value estimated by estimating means on the basis of the shifted voltage-current characteristic, thereby a present open circuit voltage of the battery is computed.

Abstract: A remaining capacity measuring apparatus of this invention operates as follows. A current value and a voltage value from a current sensor and a voltage sensor respectively provided in a battery connected to a hybrid mechanism portion are sampled every 1 millisecond. Each time when eight pairs (N1) of this current value data and voltage value data are collected, the current values and voltage values are each averaged. When 100 pairs (N2) of the average current values and the average voltage values are obtained, the 100 pair data are plotted on a voltage-current coordinate system. A correlation between the current and voltage is obtained based on the plural data plotted on this coordinate system. When a strong negative correlation is indicated, an approximate line indicating a relation between the voltage and current is obtained. By substituting a predetermined current value for this line, a voltage value is defined and a value corresponding to this voltage value is regarded as a current remaining capacity.

Abstract: The temperature of a battery is detected by a temperature sensor, and a gassing voltage based on the temperature is determined by a gassing detection processing section at all times, and even during traveling, a full charge capacity calculation processing section estimates a full charge capacity on the axis of the full charge capacity from when the gassing occurred, from the remaining capacity at the time of gassing and a chargeable capacity.