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Method and apparatus for estimating state of charge of secondary battery

  • US 7,355,411 B2
  • Filed: 09/29/2004
  • Issued: 04/08/2008
  • Est. Priority Date: 10/01/2003
  • Status: Active Grant
First Claim
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1. A method for estimating a state of charge of a secondary battery, comprising the steps of:

  • preparing a switch in a charge/discharge path of the secondary battery;

    turning on the switch to connect the charge/discharge path of the secondary battery;

    calculating a no-load voltage of the secondary battery when the charge/discharge path of the secondary battery is in a connected state;

    turning off the switch to disconnect the charge/discharge path of the secondary battery;

    measuring an open-circuit voltage of the secondary battery when the charge/discharge path of the secondary battery is in a disconnected state;

    storing a polarized voltage of the secondary battery;

    calculating an electromotive force of the secondary battery by subtracting the stored polarized voltage from one of the calculated no-load voltage and the measured open-circuit voltage; and

    estimating the state of charge of the secondary battery based on the calculated electromotive force.

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