Device and method for continuously equalizing the charge state of lithium ion battery cells
First Claim
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1. A method of equalizing charge states of individual cells in a battery, the method comprising:
- measuring a previous cell voltage for each cell;
measuring a previous shunt current for each cell;
calculating, based on the previous cell voltage and the previous shunt current, an adjusted cell voltage for each cell;
determining a lowest adjusted cell voltage from among the calculated adjusted cell voltages; and
calculating a new shunt current for each cell, wherein the calculating the new shunt current for each cell comprises;
setting the new shunt current for the cell having the lowest adjusted cell voltage to zero; and
calculating a new shunt current for each of the remaining cells according to the following equation;
ISNn =(Δ
CTp)(VNpi −
VLpi)/(B)(VH-VL), whereISNn is the new shunt current,Δ
CTp is the difference between the nominal battery capacity at charge termination and the nominal battery capacity at discharge termination at temperature Tp,VNpi is the adjusted cell voltage,VLpi is the lowest adjusted cell voltage from among the adjusted cell voltages of each of the N cells,B is the target time to substantially fully equalize the charge states,VH is the cell charge voltage limit, andVL is the cell discharge voltage limit.
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Abstract
A method of equalizing charge states of individual cells in a battery includes measuring a previous cell voltage for each cell, measuring a previous shunt current for each cell, calculating, based on the previous cell voltage and the previous shunt current, an adjusted cell voltage for each cell, determining a lowest adjusted cell voltage from among the calculated adjusted cell voltages, and calculating a new shunt current for each cell.
26 Citations
10 Claims
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1. A method of equalizing charge states of individual cells in a battery, the method comprising:
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measuring a previous cell voltage for each cell; measuring a previous shunt current for each cell; calculating, based on the previous cell voltage and the previous shunt current, an adjusted cell voltage for each cell; determining a lowest adjusted cell voltage from among the calculated adjusted cell voltages; and calculating a new shunt current for each cell, wherein the calculating the new shunt current for each cell comprises; setting the new shunt current for the cell having the lowest adjusted cell voltage to zero; and calculating a new shunt current for each of the remaining cells according to the following equation;
ISNn =(Δ
CTp)(VNpi −
VLpi)/(B)(VH-VL), whereISNn is the new shunt current, Δ
CTp is the difference between the nominal battery capacity at charge termination and the nominal battery capacity at discharge termination at temperature Tp,VNpi is the adjusted cell voltage, VLpi is the lowest adjusted cell voltage from among the adjusted cell voltages of each of the N cells, B is the target time to substantially fully equalize the charge states, VH is the cell charge voltage limit, and VL is the cell discharge voltage limit. - View Dependent Claims (2, 3)
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4. A device for equalizing charge states of individual cells in a battery, the device comprising:
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control circuitry including a voltage sense amplifier which measures a previous cell voltage for each cell, a current sense amplifier which measures a previous shunt current for each cell, a part which calculates, based on the previous cell voltage and the previous shunt current, an adjusted cell voltage for each cell, a part which determines a lowest adjusted cell voltage from among the calculated adjusted cell voltages, and a part which calculates a new shunt current for each cell, wherein the part which calculates the new shunt current for each cell; sets the new shunt current for the cell having the lowest adjusted cell voltage to zero; and calculates new shunt currents for each of the remaining cells according to the following equation;
ISNn =(Δ
CTp)(VNpi −
VLpi)/(B)(VH-VL), whereISNn is the new shunt current, Δ
CTp is the difference between the nominal battery capacity at charge termination and the nominal battery capacity at discharge termination at temperature Tp,VNpi is the adjusted cell voltage, VLpi is the lowest adjusted cell voltage from among the adjusted cell voltages of each of the N cells, B is the target time to substantially fully equalize the charge states, VH is the cell charge voltage limit, and VL is the cell discharge voltage limit. - View Dependent Claims (5, 6, 7, 8, 9)
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10. A system for equalizing battery cell charge states, the system comprising:
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a battery including first through eighth cells; a first control circuit corresponding to the first and second cells; a second control circuit corresponding to the third through fifth cells; and a third control circuit corresponding to the sixth through eighth cells, wherein each of the first through third control circuits comprises; a voltage sense amplifier which measures a previous cell voltage for each of the corresponding cells; a current sense amplifier which measures a previous shunt current for each of the corresponding cells; a part which calculates, based on the previous cell voltage and the previous shunt current, an adjusted cell voltage for each of the corresponding cells; a part which determines a lowest adjusted cell voltage from among the calculated adjusted cell voltages; and a part which calculates a new shunt current for each of the corresponding cells, and wherein the part which calculates the new shunt current for each of the corresponding cells; sets the new shunt current for the cell having the lowest adjusted cell voltage to zero; and calculates new shunt currents for each of the remaining cells according to the following equation;
ISNn =(Δ
CTp)(VNpi −
VLpi)/(B)(VH-VL), whereISNn is the new shunt current, Δ
CTp is the difference between the nominal battery capacity at charge termination and the nominal battery capacity at discharge termination at temperature Tp,VNpi is the adjusted cell voltage, VLpi is the lowest adjusted cell voltage from among the adjusted cell voltages of each of the N cells, B is the target time to substantially fully equalize the charge states, VH is the cell charge voltage limit, and VL is the cell discharge voltage limit.
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Specification