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State of charge indicator

  • US 6,127,806 A
  • Filed: 05/14/1999
  • Issued: 10/03/2000
  • Est. Priority Date: 05/14/1998
  • Status: Active Grant
First Claim
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1. A state of charge indicator for a battery comprising plural cells connected in series, the indicator comprising:

  • a display device;

    a sensor which detects an open circuit voltage of the battery;

    a sensor which detects a charging/discharging current of the battery; and

    a microprocessor programmed to;

    compute an open circuit voltage of a cell based on the detected battery open circuit voltage;

    compute an SOC (state of charge) corresponding to the computed cell open circuit voltage from an SOC-cell open circuit voltage characteristic map obtained by defining the battery charge amount when the open circuit voltage of the cell is a first predetermined voltage as SOC 100%, and defining the battery charge amount when the open circuit voltage of the cell is a second predetermined voltage as SOC 0%, wherein the open circuit voltage of the cell is in a range between the second predetermined voltage and the first predetermined voltage, the second predetermined voltage being set to be lower than the first predetermined voltage;

    compute the SOC by integrating the detected charging/discharging current when the open circuit voltage of the cell is greater than the first predetermined voltage; and

    display the computed SOC in the display device.

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