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Charging device of a secondary battery for controlling termination of charging in response to the change state of terminal voltage of the secondary battery

  • US 5,432,426 A
  • Filed: 06/29/1993
  • Issued: 07/11/1995
  • Est. Priority Date: 07/10/1992
  • Status: Expired due to Term
First Claim
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1. A charging device of a secondary battery for detecting terminal voltage of the secondary battery during charging for controlling termination of a charging operation, said charging device comprising:

  • means for supplying a charging current to the secondary battery;

    means for detecting a terminal voltage of said secondary battery;

    most recent gradient calculation means for finding a most recent gradient of the terminal voltage detected by said detection means;

    average gradient calculation means for finding an average gradient, for a comparatively long term, of the terminal voltage detected by said detection means;

    gradient comparison means for comparing said most recent gradient with said average gradient;

    voltage comparison means for comparing the most recent terminal voltage with a previously measured terminal voltage;

    termination determination means responsive to outputs of said gradient comparison means and said voltage comparison means for determining termination of charging by the fact that said most recent terminal voltage becomes equal to or less than said previously measured terminal voltage at a time after said most recent gradient becomes greater than said average gradient by at least a predetermined value; and

    control means responsive to said termination determination means for controlling said charging current supply means so as to stop the charging current to the secondary battery.

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