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Method for opportunistically balancing charge between battery cells

  • US 9,450,426 B2
  • Filed: 03/07/2012
  • Issued: 09/20/2016
  • Est. Priority Date: 03/07/2011
  • Status: Active Grant
First Claim
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1. A method for balancing charge between battery cells, comprising:

  • estimating an amount of charge stored in a first battery cell in response to an open circuit voltage of the first battery cell, the open circuit voltage in a first voltage region of battery cell output voltage;

    estimating an amount of charge stored in a second battery cell in response to an open circuit voltage of the second battery cell, the open circuit voltage in the first voltage region of battery cell output voltage;

    reducing a total charge capacity of the first or second battery cell from a rated charge storage capacity in response to an open circuit voltage of the first or second battery cell and an integrated charge capacity of the first or second battery cell;

    balancing charge of the first or second battery cell in a second voltage region of battery cell output voltage in an amount of charge related to a difference between the amount of charge stored in the first battery cell in the first voltage region of battery cell output voltage and the amount of charge stored in the second battery cell in the first voltage region of battery cell output voltage, where a slope of battery voltage versus battery charge of the first voltage region is higher than a slope of battery voltage versus battery charge of the second voltage region, and where a battery voltage of the first voltage region is lower than a battery voltage of the second voltage region; and

    adjusting a timing of the balancing of charge of the first or second battery cell in response to reducing the rated charge storage capacity of the first or second battery cell.

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