Patent ID: 7728598

Claim:
A method for estimating a charge/discharge electricity amount of a secondary battery comprising: measuring a pair of data consisting of a current flowing through the secondary battery and a terminal voltage of the secondary battery corresponding to the current, thus obtaining a plurality of pairs of data; if specific selection conditions are satisfied, the specific selection conditions including (i) the current in charging and discharging the secondary battery is within a first predetermined range, (ii) a number of the plurality of pairs of data greater than or equal to a predetermined number, and (iii) a charge/discharge electricity amount during collection of the plurality of pairs of data is within a second predetermined range, calculating a no-load voltage as a voltage intercept at a current of zero in a straight-line approximation obtained by statistical processing with respect to the plurality of pairs of data; if the specific selection conditions are not satisfied and if one of specific current conditions or voltage conditions continue to be met for a certain amount of time, calculating an open circuit voltage from the terminal voltage of the secondary battery, the component resistance of the secondary battery and an average current; calculating a change (ΔV b ) in the no-load voltage or the open circuit voltage over a predetermined period of time; calculating an estimated charge/discharge electricity amount (ΔQ e ) of the secondary battery based on the change in the no-load voltage or the open circuit voltage; and calculating a measured charge/discharge electricity amount over the predetermined period of time from the current flowing through the secondary battery.