Patent ID: 8581555

Claim:
The secondary battery system comprising: a battery controller which controls charge and discharge of a secondary battery; a total controller which controls the entire system; an ammeter which detects a charge current and a discharge current of the secondary battery; a voltmeter which detects a voltage of the secondary battery, and determination means for obtaining a direct current resistance of the secondary battery at the time of charge and a direct current resistance of the secondary battery at the time of discharge on the basis of a current value and a voltage value detected by the ammeter and the voltmeter, to thereby determine a temporary increase in the direct current resistance of the secondary battery caused by charge and discharge with a current on the basis of a relation between the two obtained direct current resistances, wherein the determination means calculates a value of a ratio of the direct current resistance of the secondary battery at the time of the discharge to the direct current resistance of the secondary battery at the time of the charge (discharge resistance/charge resistance), and determines, when the calculated value of the ratio of the direct current resistances of the secondary battery decreases to be equal to or smaller than a predetermined value, the temporary increase in the direct current resistance of the secondary battery caused by the charge and discharge with a large current, and the total controller outputs, when the determination means determines the temporary increase in the direct current resistance of the secondary battery, a signal for stopping a use of the secondary battery for a given period via the battery controller, to thereby suspend the charge and discharge of the secondary battery.