Patent ID: 7492126

Claim:
A secondary cell residual capacity calculation method, comprising: detecting a temperature of a plurality of secondary cells; detecting a current and a terminal voltage of each of the secondary cells; digitizing the temperature, the current, and the terminal voltage; calculating a cell polarization voltage from the digitized temperature, current and terminal voltage; calculating an original cell voltage from both of the calculated cell polarization voltage and the detected terminal voltage; calculating a temporary residual capacity rate based on the calculated original cell voltage with reference to a prearranged cell voltage-to-residual capacity reference data table, wherein the prearranged cell voltage-to-residual capacity reference data table may be used regardless of whether the cell is charging or discharging; determining whether the secondary cell is charging or discharging; and determining a relative residual capacity rate, wherein if the cell is discharging, the relative residual capacity rate is determined by: calculating a final discharge prediction point; obtaining a whole cell discharge capacity in a loaded condition thereof; and calculating the relative residual capacity rate based on the temporary residual capacity rate, the final discharge prediction point and the whole cell discharge capacity, wherein the step of determining the relative residual capacity rate involves reference to one data table, and wherein the one data table is the prearranged cell voltage-to-residual capacity reference data table.