Patent ID: 8036787

Claim:
A control device for a rechargeable power storage device mounted on a vehicle, said power storage device being connected to a load via a connecting unit, said connecting unit changing from a non-conduction state to a conduction state when an operation of said power storage device starts, and changing from said conduction state to said non-conduction state when the operation of said power storage device ends, said control device comprising: a calculating unit that (i) calculates a first value indicating a state of charge of said power storage device based on an open voltage of said power storage device when the operation of said power storage device starts and before said connecting unit is brought into the conduction state, and (ii) calculates said state of charge of said power storage device based on an initial value of said state of charge of said power storage device and charging/discharging electric power of said power storage device while said connecting unit is in the conduction state; a storage unit that receives said state of charge of said power storage device calculated by said calculating unit based on the initial value and stores said state of charge as a second value, when the operation of said power storage device ends; and a selecting unit that selects said first value as said initial value when a predetermined condition is satisfied, and selects said second value as said initial value when said predetermined condition is not satisfied, said predetermined condition being defined as a condition that is satisfied in a case where said calculating unit is able to calculate said first value and in a case where an absolute value of a difference between said first value and said second value is larger than a reference value defined based on said first value and a temperature when the operation of said power storage device ends.