Patent ID: 8903667
Filing Date: 2014-12-02
Classification: G01R

Abstract:
1. A state-of-charge estimation method, wherein change over time of an open-circuit voltage (OCV) of a secondary battery after completion of charge/discharge is approximated with a voltage characteristic formula having an adjustment parameter, and the open-circuit voltage in a stable condition of the secondary battery is calculated from the voltage characteristic formula to estimate the state of charge of the secondary battery, the method comprising: obtaining m (m is a natural number) voltage measurement values of the open-circuit voltage of the secondary battery in a given cycle during a given data acquisition period after completion of charge/discharge of the secondary battery; selecting the voltage measurement value at given selection timing from the m voltage measurement values to use as a selected voltage measurement value; calculating the initial value of the adjustment parameter based on the selected voltage measurement value and the selection timing; calculating a convergence value of the adjustment parameter by gradually correcting the adjustment parameter from the initial value so that the error between the open-circuit voltage calculated with the voltage characteristic formula and the m voltage measurement values is the smallest; calculating the open-circuit voltage in the stable condition by using the convergence value of the adjustment parameter for the voltage characteristic formula; and estimating the state of charge of the secondary battery from the open-circuit voltage in the stable condition.