| 摘要 |
PROBLEM TO BE SOLVED: To perform discrimination of charging period, without being influenced by the dispersion of quality in every battery and the deterioration of batteries. SOLUTION: A secondary battery 20 is made to perform pulse discharging via a load resistor at every preset time, and the voltage of the secondary battery 220 before pulse discharging and during pulse discharge is detected, and based on this detected voltage, the internal resistance of the secondary battery 220 is computed, and the charging period voltage which is the voltage of the secondary battery equivalent to the period to perform charging is discriminated, so that when the voltage under this charging period voltage is detected, it can be made the period to perform charging without fail, therefore the charge period can be discriminated accurately with a simple constitution, without being influenced by increase in the internal resistance accompanying the dispersion of quality by every battery and the deterioration. As a result, a user can be accurately informed of charging timing.
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