Method and system for cell equalization using state of charge
First Claim
1. A method for cell equalization in battery packs, comprising:
- determining a state-of-charge for each cell of a plurality of cells;
determininga charge capacity performed byi) calculating a difference between a selected maximum state-of-charge for said each cell and a present state-of-charge for said each cell,ii) multiplying said difference by a total capacity for each said cell or by a nominal capacity for said each cell, andiii) employing a Coulombic efficiency calculation; and
equalizing one or more cells of said plurality of cells, when the charge capacity of at least one cell of said plurality of cells is lower than a charge capacity of an other cell of said plurality of cells by a selected threshold.
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Abstract
The present invention relates to an implementation of a method for cell equalization. The present invention uses other information such as the individual cell state-of-charge (SOC) estimates, and individual capacities and/or cell Coulombic efficiencies, possibly available from a dual extended Kalman filter. The present invention defines or refers to an operational SOC range between a minimum and a maximum. The minimum and maximum could be constants or could be dynamic based on functions of other variables. SOC can be measured relative to maximum charge or relative to maximum discharge for each cell. When the SOC is not consistent across the cells, a prioritizing scheme is used to determine which cells require equalization.
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Citations
25 Claims
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1. A method for cell equalization in battery packs, comprising:
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determining a state-of-charge for each cell of a plurality of cells; determining a charge capacity performed by i) calculating a difference between a selected maximum state-of-charge for said each cell and a present state-of-charge for said each cell, ii) multiplying said difference by a total capacity for each said cell or by a nominal capacity for said each cell, and iii) employing a Coulombic efficiency calculation; and equalizing one or more cells of said plurality of cells, when the charge capacity of at least one cell of said plurality of cells is lower than a charge capacity of an other cell of said plurality of cells by a selected threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A system for cell equalization in battery packs, comprising:
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a battery pack with a plurality of cells; a sensor in operable communication with at least two cells of said plurality of cells configured to facilitate determination of state of charge for each cell of said at least two cells; and a controller in operable communication with said sensor and said plurality of cells for determining a charge capacity performed by i) calculating a difference between a selected maximum state-of-charge for said each cell and a present state-of-charge for said each cell, ii) multiplying said difference by a total capacity for each said cell or by a nominal capacity for said each cell, and iii) employing a Coulombic efficiency calculation; wherein said controller is configured to equalize charge of each cell of said at least two cells of said plurality of cells based on the state-of-charge for each cell of said plurality of cells. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A system for cell equalization in battery packs, comprising:
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a means for determining a state-of-charge for each cell of a plurality of cells; a means for determining a charge capacity performed by i) calculating a difference between a selected maximum state-of-charge for said each cell and a present state-of-charge for said each cell, ii) multiplying said difference by a total capacity for each said cell or by a nominal capacity for said each cell, and iii) employing a Coulombic efficiency calculation; and a means for equalizing one or more cells of said plurality of cells, when the charge capacity of at least one cell of said plurality of cells is lower than a charge capacity of an other cell of said plurality of cells by a selected threshold.
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24. A storage medium encoded with a machine-readable computer program code, wherein said storage medium includes instructions for causing a computer to implement a method for cell equalization in battery packs comprising:
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determining a state-of-charge for each cell of a plurality of cells; determining a charge capacity performed by i) calculating a difference between a selected maximum state-of-charge for said each cell and a present state-of-charge for said each cell, ii) multiplying said difference by a total capacity for each said cell or by a nominal capacity for said each cell, and iii) employing a Coulombic efficiency calculation; and equalizing one or more cells of said plurality of cells, when the charge capacity of at least one cell of said plurality of cells is lower than a charge capacity of an other cell of said plurality of cells by a selected threshold.
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25. A computer data signal embodied in a computer readable medium said computer data signal comprising code configured to cause a computer to implement a method for cell equalization in battery packs comprising:
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determining a state-of-charge for each cell of a plurality of cells; determining a charge capacity performed by i) calculating a difference between a selected maximum state-of-charge for said each cell and a present state-of-charge for said each cell, ii) multiplying said difference by a total capacity for each said cell or by a nominal capacity for said each cell, and iii) employing a Coulombic efficiency calculation, and a discharge capacity for each cell of said plurality of cells; and equalizing one or more cells of said plurality of cells, when the charge capacity of at least one cell of said plurality of cells is lower than a charge capacity of an other cell of said plurality of cells by a selected threshold.
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Specification