DEVICE FOR ESTIMATING STATE OF CHARGE OF BATTERY

A battery SoC estimation device includes a discharge-and charge current detection means 1, a terminal-voltage detection means 2, a current-integration SoC estimation means 3, an open-circuit-voltage SoC estimation means 4, an error estimation means 6, and an SoC calculating means 7. The estimation means 3estimates a current-integration-method SoC (SoC i ), calculating variance of current-integration-method SoC based on information on detection accuracy of the detection means 1. The estimation means 4 estimates an open-circuit-voltage-method SoC (SoC v ) corresponding to an open circuit voltage value estimated based on a discharge-and-charge current value and a terminal voltage value, using a battery equivalent circuit model. The estimation means 6 estimates an estimate error n i of the current-integration-method SoC based on a difference between the SoC v and the SoC i , variance of the SoC i , and variance of the SoC v . The calculating means 7 calculates SoC of a battery based on the SoC i and the n i .