| 摘要 |
PROBLEM TO BE SOLVED: To provide a secondary battery charging method that is controlled, in such a way as to prevent overcharge by normally observing the charging state of the charged battery with respect to the kinds of the secondary batteries and charging conditions. SOLUTION: The rate of change with time (di(t)/dt) of a charging current and that (de(t)/dt) of a charge impressing voltage at that time are each measured. Their ratio (di(t)/de(t)) is calculated, so that control deviation between the ratio and a first set value (target value) inputted in advance is calculated to control the control deviation, in such a way as to minimize it at all times. Also, a voltage value when the ratio has reached within a given ratio from a second set value is controlled, in such a way as to be held as a charge- impressing voltage. Alternatively, in the initial charging stage of a secondary battery 5, the first set value can be calculated and set automatically from the numerical data obtained by sampling the ratio a few number of times.
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