| 摘要 |
PROBLEM TO BE SOLVED: To further improve the detection accuracy of the full charge of a secondary battery, and to further surely prevent overcharge. SOLUTION: The fullharge is determined when internal resistance is lowered exceeding a prescribed value, when the ratio of the internal resistance to the charge capacity of the secondary battery reaches negative from positive. As the characteristic of the internal resistance R against the charge capacity Ah, timing when the peak of the resistance appears is early compared with the characteristic of a similar voltage Vb between terminals, and the peak appears well in advance even if compared with timing when the battery actually reaches the full charge. Therefore, when the peak of the internal resistance R appears, the timing when the internal resistance is lowered exceeding the prescribed value is determined as the full charge on the basis of a time when a rate of changeΔR/ΔAh, whereinΔR is a volume of change of the internal resistance relative to the charge capacityΔAh when the rate reaches zero, thus further improving the detection accuracy of the full charge. By controlling charge to the secondary battery using the detected result, the overcharge is further surely prevented. COPYRIGHT: (C)2004,JPO
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