BATTERY MANAGEMENT SYSTEM
First Claim
1. A battery management system for determining a state of capacity of a lithium ion cell comprising:
- a) a voltage detector coupled to the cell for obtaining first and second terminal voltage measurements of the cell;
b) a coulomb detector coupled to the cell for counting the number of coulombs discharged from the cell during a controlled discharge of the cell that occurs between the first and second terminal voltage measurements;
c) an electronic control unit coupled to the voltage and coulomb detectors, the electronic control unit calculating the state of capacity of the cell from the number of coulombs discharged from the cell during the controlled discharge and from the first and second terminal voltage measurements of the cell.
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Accused Products
Abstract
Disclosed herein is a battery management system for lithium ion batteries capable of determining a battery pack'"'"'s state of capacity; determining a battery pack'"'"'s state of charge limits; adjusting for voltage drops and power losses over a battery'"'"'s internal and/or connector impedances; adjusting the upper and lower voltage limits of a battery pack; and of actively balancing the cells making up the battery pack. In order to achieve this functionality, the battery pack management system includes an electronic control unit, which unit is coupled to module and cell-level circuitry that is designed to measure operating conditions of the battery such as voltage and current at any given time.
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Citations
24 Claims
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1. A battery management system for determining a state of capacity of a lithium ion cell comprising:
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a) a voltage detector coupled to the cell for obtaining first and second terminal voltage measurements of the cell; b) a coulomb detector coupled to the cell for counting the number of coulombs discharged from the cell during a controlled discharge of the cell that occurs between the first and second terminal voltage measurements; c) an electronic control unit coupled to the voltage and coulomb detectors, the electronic control unit calculating the state of capacity of the cell from the number of coulombs discharged from the cell during the controlled discharge and from the first and second terminal voltage measurements of the cell. - View Dependent Claims (2)
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3. A method of determining a state of capacity of a lithium ion cell comprising:
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a) determining a first state of charge of the cell; b) performing a controlled discharge of the cell; c) counting charge discharged from the cell during the controlled discharge; d) determining a second state of charge of the cell; and e) calculating the state of capacity of the cell based on the charge discharged from the cell during the controlled discharge and on the difference between the first state of charge and the second state of charge. - View Dependent Claims (4, 5)
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6. A battery management system for balancing the state of charge of cells in series of a battery pack, the system comprising:
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a) a voltage detector coupled to the cells for measuring a voltage of each cell of the battery pack; b) a switch in communication with a selected cell for allowing current to flow from the selected cell of the battery pack; c) a load resistor in communication with the selected cell for receiving the current flow from the selected cell; and d) a cell balancing integrated circuit in communication with the voltage detector, the switch and the load resistor, the cell balancing integrated circuit calculating a reference voltage of the cells of the battery pack VREF based on the measured voltage of each cell, determining which cell of the battery pack has a higher voltage than VREF, and discharging the cell with a higher voltage than VREF by closing the switch associated with the cell that has a higher voltage than VREF until the voltage of cell that has a higher voltage than VREF has a voltage substantially equal to VREF. - View Dependent Claims (7, 8, 9, 10)
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11. A method of balancing the state of charge of cells in series of a battery pack comprising the steps of:
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a) measuring the voltage of each cell in the battery pack; b) determining a reference voltage of the cells of the battery pack VREF; and c) discharging any cell which has a voltage higher than VREF on to a load until the voltage of that cell is substantially equal to VREF. - View Dependent Claims (12, 13, 14)
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15. A battery management system for adjusting the state of charge limits on a lithium ion cell comprising
a) a voltage detector coupled to the cell for measuring a terminal voltage of the cell; - and
b) an electronic control unit in communication with the voltage detector, the electronic control unit determining an operating range of the cell and calculating the terminal voltages that correspond to the operating range.
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16. A method of adjusting the state of charge limits on a lithium ion cell comprising
a) obtaining an operating range of a lithium ion cell; - and
b) adjusting the terminal voltage of the cell to correspond to the operating range.
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17. A battery management system for adjusting an upper voltage limit VUL and a lower voltage limit VLL of a lithium ion cell, the system comprising:
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a current detector in communication with the cell for measuring the current flowing through the cell ICELL; and an electronic control unit in communication with the current detector, the electronic control unit having the internal resistance of the cell Rinternal, VUL and VLL, the electronic control unit calculating a modified upper voltage limit VUL′ and
a modified lower voltage limit VLL′
from VUL, VLL, ICELL, and Rinternal. - View Dependent Claims (18, 19)
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20. A method of adjusting an upper voltage limit VUL and a lower voltage limit VLL of a lithium ion cell comprising the steps of
a) measuring the current flowing through the cell ICELL; b) calculating a modified upper voltage limit VUL′ and
a modified lower voltage limit VLL′
from VUL, VLL, ICELL, and a known internal resistance of the cell Rinternal.- View Dependent Claims (21, 22)
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23. A battery management system for modifying a capacity of a lithium ion cell based on current flowing through the cell, the battery management system comprising:
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a current detector for measuring the current flowing through the battery pack I; an electronic control unit having the internal impedance of the battery pack Z, the electronic control unit calculating power loss Plo as a result of Z using formula II
I2×
Z=Plo
(II); andthe electronic control unit adapted to decrease the capacity of the cell by an amount proportional to Plo.
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24. A method of modifying a capacity of a lithium ion cell based on current flowing through the cell, the method comprising the steps of:
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a) measuring the current flowing through the cell I; b) calculating power loss Plo based on a known internal impedance of the battery pack Z, using formula 11
I2×
Z=Plo
(II); andc) decreasing the capacity of the cell by an amount proportional to Plo.
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Specification