| 摘要 |
PROBLEM TO BE SOLVED: To correctly indicate the life of a secondary battery. SOLUTION: An index indicating a rate of decreasing the life of a secondary battery 14 previously measured corresponding to the discharged amount of the secondary battery 14 in the case where the secondary battery 14 is fully charged every discharge is stored in FROM 34 according to discharge amount. Discharged time at every use of the secondary battery 14 is measured with a timer circuit 24, and discharged amount is calculated with a control circuit 26. An index corresponding to the discharged amount calculated on reference to the FROM 34 from the calculated discharged amount is obtained. The life of the secondary battery 14 after use of this time is calculated on the basis of the index obtained every use until use of this time and the maximum life of the secondary battery 14 with the control circuit 26, and the life of the secondary battery 14 is judged whether the life is expired or not in accordance with whether the calculated life is smaller than the predetermined value or larger than it.
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