Battery soc estimation device

A battery State-of-Charge estimation device comprising:

• a discharge-and-charge current detection means that detects a discharge-and-charge current value of a battery;
• a terminal voltage detection means that detects a terminal voltage value of the battery,
• a current-integration-method State-of-Charge estimation means that estimates a current-integration-method State-of-Charge based on a State-of-Charge obtained by integrating the discharge-and-charge current value inputted from the discharge-and-charge current detection means and a State-of-Charge obtained at previous time, calculating a variance of the current-integration-method State-of-Charge based on information on a detection accuracy of the discharge-and-charge current detection means;
• an open-circuit-voltage method State-of-Charge estimation means that estimates an open-circuit-voltage State-of-Charge based on the discharge-and-charge current value inputted from the discharge-and-charge current detection means and the terminal voltage value inputted from the terminal voltage detection means, using a battery equivalent circuit model, the open-circuit-voltage method State-of-Charge estimation means calculating a variance of the open-circuit-voltage method State-of-Charge based on information of detection accuracy of the discharge-and-charge current detection means and the terminal voltage detection means;
• an error estimation means that estimates an estimate error of the current-integration-method State-of-Charge based on a difference between the open-circuit-voltage method State-of-Charge and the current-integration-method State-of-Charge, the variance open-circuit-voltage method State-of-Charge of current-integration-method State-of-Charge, and the variance of;
• and
• a State-of-Charge calculating means that calculates a State-of-Charge of the battery based on the current-integration-method State-of-Charge and the estimate error estimated by the error estimation means.