Patent ID: 7200499

Claim:
A calculation device calculating an available capacity of a secondary battery, comprising: voltage detection means for detecting a value in voltage of said secondary battery; current detection means for detecting a value of a current of said secondary battery; means for calculating as based on said value in voltage of said secondary battery a first correction parameter employed in calculating an available capacity of said secondary battery; means for calculating as based on said value of said current of said secondary battery a second correction parameter employed in calculating said available capacity of said secondary battery; and calculation means using said value in voltage, said value of said current and said first and second correction parameters for calculating said available capacity of said secondary battery, wherein said second correction parameter is increased when said secondary battery is charged/discharged by a current larger in absolute value, and said second correction parameter is decreased when said secondary battery is charged/discharged by a current smaller in absolute value, wherein said calculation device prevents at least one excessive discharging and excessive charging of said secondary battery based on the calculated available capacity of said secondary battery.