Patent ID: 8405356

Claim:
A full charge capacity value correction circuit, comprising: a current detection portion which detects a current value of current flowing in a secondary battery; a voltage detection portion which detects a terminal voltage value of the secondary battery; a capacity storage portion which stores a full charge capacity value indicating a full charge capacity of the secondary battery; a remaining quantity calculation portion which calculates, as an accumulated remaining quantity, a remaining charging quantity in the secondary battery from a total value obtained by cumulatively adding charged electrical quantities and subtracting discharged electrical quantities in the secondary battery, based on charge/discharge currents of the secondary battery detected by the current detection portion; a remaining quantity estimation portion which estimates, as an estimated remaining quantity, a remaining quantity of the secondary battery by using a terminal voltage value detected by the voltage detection portion; and a full charge capacity value correction portion which calculates, when the estimated remaining quantity estimated by the remaining quantity estimation portion becomes equal to a reference value set in advance, a difference electrical quantity, which is equivalent to a difference between the estimated remaining quantity estimated by the remaining quantity estimation portion and the accumulated remaining quantity calculated by the remaining quantity calculation portion, and performs correction, in a case where the estimated remaining quantity is greater than the accumulated remaining quantity, by adding the difference electrical quantity to the full charge capacity value stored in the capacity storage portion, but in a case where the estimated remaining quantity is less than the accumulated remaining quantity, by subtracting the difference electrical quantity from the full charge capacity value stored in the capacity storage portion, wherein the remaining quantity calculation portion uses, when the estimated remaining quantity becomes equal to the reference value, the estimated remaining quantity as a new accumulated remaining quantity to update the accumulated remaining quantity.