US20040135544A1 — System and method for determining and balancing s…

Claim 1

Independent Claim 79 words

1 . A method for determining state of charge of plural series connected electrical energy storage units, comprising: applying a non-dissipative load to a selected storage unit in a string of electrical energy storage units, resulting in an energy transfer between the selected storage unit and the string of storage units through the non-dissipative load; and determining state of charge of the selected unit from voltage and current data of the selected storage unit resulting from the energy transfer.

Claim 2

Dependent Claim 79 words

1 . A method for determining state of charge of plural series connected electrical energy storage units, comprising: applying a non-dissipative load to a selected storage unit in a string of electrical energy storage units, resulting in an energy transfer between the selected storage unit and the string of storage units through the non-dissipative load; and determining state of charge of the selected unit from voltage and current data of the selected storage unit resulting from the energy transfer.

Claim 3

Dependent Claim 15 words

2 . The method of claim 1 wherein the energy is transferred by pulsed currents.

Claim 4

Dependent Claim 38 words

3 . The method of claim 1 wherein determining the state of charge of the selected storage unit comprises: calculating an impedance of the selected storage unit from the voltage and current data obtained during the energy transfer.

Claim 5

Dependent Claim 125 words

4 . A method for balancing state of charge among plural series connected electrical energy storage units, comprising: applying a non-dissipative load to a selected storage unit in a string of electrical energy storage units, resulting in an energy transfer between the selected storage unit and the string of storage units through the non-dissipative load; determining state of charge of the selected unit from voltage and current data of the selected storage unit resulting from the energy transfer; and when the state of charge of the selected unit is different than a target state of charge, transferring energy between the selected unit and the string of storage units, such that the state of charge of the selected unit converges toward the target state of charge.

Claim 6

Dependent Claim 125 words

4 . A method for balancing state of charge among plural series connected electrical energy storage units, comprising: applying a non-dissipative load to a selected storage unit in a string of electrical energy storage units, resulting in an energy transfer between the selected storage unit and the string of storage units through the non-dissipative load; determining state of charge of the selected unit from voltage and current data of the selected storage unit resulting from the energy transfer; and when the state of charge of the selected unit is different than a target state of charge, transferring energy between the selected unit and the string of storage units, such that the state of charge of the selected unit converges toward the target state of charge.

Claim 7

Dependent Claim 33 words

5 . The method of claim 4 , comprising: applying an up-converter to the selected storage unit; and transferring units of energy from the selected storage unit to the string of storage units.

Claim 8

Dependent Claim 33 words

6 . The method of claim 4 , comprising: applying a down-converter to the selected storage unit; and transferring units of energy from the string of storage units to the selected storage unit.

Claim 9

Dependent Claim 39 words

7 . The method of claim 4 , wherein determining the state of charge of the selected storage unit comprises: calculating an impedance of the selected storage unit from the voltage and current data obtained during the energy transfer.

Claim 10

Dependent Claim 81 words

8 . The method of claim 7 , wherein determining the state of charge of the selected storage unit further comprises: applying the non-dissipative load to the selected storage unit; determining a first voltage across the selected storage unit; determining a first current flowing through the selected storage unit; determining a second voltage from the first current and impedance of the selected storage unit; and determining the state of charge based on a voltage difference between the first and second voltages.

Claim 11

Dependent Claim 16 words

9 . The method of claim 4 , wherein the energy is transferred by pulsed current.

Claim 12

Dependent Claim 18 words

10 . The method of claim 4 , wherein each of the storage units is a storage cell.

Claim 13

Dependent Claim 18 words

11 . The method of claim 4 , wherein each of the storage units is a battery module.

Claim 14

Dependent Claim 20 words

12 . The method of claim 4 , wherein one or more of the storage units comprise a battery pack.

Claim 15

Dependent Claim 76 words

13 . The method of claim 4 , wherein for each storage unit in the string having a number of storage units, comprising: applying the non-dissipative load to a selected storage unit, resulting in an energy transfer between the selected storage unit and the string of storage units through the non-dissipative load; and determining an impedance of the selected storage unit from voltage and current data of the selected storage unit obtained during the energy transfer.

Claim 16

Dependent Claim 85 words

14 . The method of claim 13 , further comprising: determining a string impedance from the determined impedance of each storage unit; determining a first string voltage and string current from the string of storage units; determining a second string voltage from the string current and the string impedance; determining a string voltage difference between the first string voltage and the second string voltage; and determining a target state of charge as a ratio of the string voltage difference to the number of storage units.

Claim 17

Dependent Claim 64 words

15 . The method of claim 14 , further comprising: selecting a storage unit from the string of storage units having a state of charge that is different from the target state of charge; transferring energy between the selected storage unit and the string of storage units, such that the state of charge of the selected unit converges toward the target state of charge.

Claim 18

Dependent Claim 70 words

16 . The method of claim 15 , wherein selecting a storage unit from the string of storage units having a state of charge that is different from the target state of charge, comprises: comparing each of the states of charge of the individual storage units with the target state of charge; and selecting a storage unit having a state of charge most different from the target state of charge.

Claim 19

Dependent Claim 62 words

17 . The method of claim 15 , wherein selecting a storage unit from the string of storage units having a state of charge that is different from the target state of charge, comprises: selecting a storage unit having a state of charge that is different from the target state of charge from the string of storage units in a sequential order.

Claim 20

Dependent Claim 94 words

18 . The method of claim 15 , wherein transferring energy between the selected storage unit and the string of storage units, comprises: comparing the state of charge of the selected storage unit with the target state of charge; when the state of charge is less than the target state of charge, transferring energy from the string of storage units to charge the selected storage unit; and when the state of charge is greater than the target state of charge, transferring energy from the selected storage unit to charge the string of storage units.

Claim 21

Dependent Claim 41 words

19 . The method of claim 18 , comprising: when the state of charge is less than the target state of charge, transferring energy from the string of storage units to charge the selected storage unit until a charge time expires.

Claim 22

Dependent Claim 41 words

20 . The method of claim 18 , comprising: when the state of charge is greater than the target state of charge, transferring energy from the selected storage unit to charge the string of storage units until a discharge time expires.

Claim 23

Dependent Claim 78 words

21 . A system for determining state of charge of plural series connected electrical energy storage units, comprising: a non-dissipative load being applied to a selected storage unit in a string of electrical energy storage units, resulting in an energy transfer between the selected storage unit and the string of storage units; and a controller determining state of charge of the selected unit from voltage and current data of the selected storage unit resulting from the energy transfer.

Claim 24

Dependent Claim 78 words

21 . A system for determining state of charge of plural series connected electrical energy storage units, comprising: a non-dissipative load being applied to a selected storage unit in a string of electrical energy storage units, resulting in an energy transfer between the selected storage unit and the string of storage units; and a controller determining state of charge of the selected unit from voltage and current data of the selected storage unit resulting from the energy transfer.

Claim 25

Dependent Claim 16 words

22 . The system of claim 21 , wherein the energy is transferred by pulsed current.

Claim 26

Dependent Claim 30 words

23 . The system of claim 21 , wherein the controller calculates an impedance of the selected storage unit from the voltage and current data obtained during the energy transfer.

Claim 27

Dependent Claim 132 words

24 . A system for balancing state of charge of plural series connected electrical energy storage units, comprising: a non-dissipative load being applied to a selected storage unit in a string of electrical energy storage units, resulting in an energy transfer between the selected storage unit and the string of storage units; a controller determining state of charge of the selected unit from voltage and current data of the selected storage unit obtained during the energy transfer; and when the state of charge of a selected unit is different than a target state of charge, the controller directing the non-dissipative load to transfer energy between the selected storage unit and the string of storage units, such that the state of charge of the selected unit converges toward the target state of charge.

Claim 28

Dependent Claim 132 words

24 . A system for balancing state of charge of plural series connected electrical energy storage units, comprising: a non-dissipative load being applied to a selected storage unit in a string of electrical energy storage units, resulting in an energy transfer between the selected storage unit and the string of storage units; a controller determining state of charge of the selected unit from voltage and current data of the selected storage unit obtained during the energy transfer; and when the state of charge of a selected unit is different than a target state of charge, the controller directing the non-dissipative load to transfer energy between the selected storage unit and the string of storage units, such that the state of charge of the selected unit converges toward the target state of charge.

Claim 29

Dependent Claim 30 words

25 . The system of claim 24 , wherein the non-dissipative load is an up-converter transferring units of energy from the selected storage unit to the string of storage units.

Claim 30

Dependent Claim 30 words

26 . The system of claim 24 , wherein the non-dissipative load is a down-converter transferring units of energy from the string of storage units to the selected storage unit.

Claim 31

Dependent Claim 30 words

27 . The system of claim 24 , wherein the controller calculates an impedance of the selected storage unit from the voltage and current data obtained during the energy transfer.

Claim 32

Dependent Claim 78 words

28 . The system of claim 27 , wherein: the non-dissipative load is applied to the selected storage unit; the controller determines a first voltage across the selected storage unit; the controller determines a first current flowing through the selected storage unit; the controller determines a second voltage from the first current and impedance of the selected storage unit; and the controller determines the state of charge based on a voltage difference between the first and second voltages.

Claim 33

Dependent Claim 16 words

29 . The system of claim 24 , wherein the energy is transferred by pulsed current.

Claim 34

Dependent Claim 18 words

30 . The system of claim 24 , wherein each of the storage units is a storage cell.

Claim 35

Dependent Claim 18 words

31 . The system of claim 24 , wherein each of the storage units is a battery module.

Claim 36

Dependent Claim 20 words

32 . The system of claim 24 , wherein one or more of the storage units comprise a battery pack.

Claim 37

Dependent Claim 74 words

33 . The system of claim 24 , wherein for each storage unit in the string having a number of storage units: the non-dissipative load is applied to a selected storage unit, resulting in an energy transfer between the selected storage unit and the string of storage units; and the controller determines an impedance of the selected storage unit from voltage and current data of the selected storage unit observed from the energy transfer.

Claim 38

Dependent Claim 94 words

34 . The system of claim 33 , wherein: the controller determines a string impedance from the determined impedance of each storage unit; the controller determines a first string voltage and string current from the string of storage units; the controller determines a second string voltage from the string current and the string impedance; the controller determines a string voltage difference between the first string voltage and the second string voltage; and the controller determines a target state of charge as a ratio of the string voltage difference to the number of storage units.

Claim 39

Dependent Claim 73 words

35 . The system of claim 34 , wherein: the controller selects a storage unit from the string of storage units having a state of charge that is different from the target state of charge; and the controller directs the non-dissipative load to transfer energy between the selected storage unit and the string of storage units, such that the state of charge of the selected unit converges toward the target state of charge.

Claim 40

Dependent Claim 49 words

36 . The system of claim 35 , wherein: the controller compares each of the states of charge of the individual storage units with the target state of charge; and the controller selects a storage unit having a state of charge most different from the target state of charge.

Claim 41

Dependent Claim 39 words

37 . The system of claim 35 , wherein: the controller selects a storage unit having a state of charge that is different from the target state of charge from the string of storage units in a sequential order.

Claim 42

Dependent Claim 96 words

38 . The system of claim 35 , wherein: the controller compares the state of charge of the selected storage unit with the target state of charge; when the state of charge is less than the target state of charge, the controller directing the non-dissipative load to transfer energy from the string of storage units to charge the selected storage unit; and when the state of charge is greater than the target state of charge, the controller directing the non-dissipative load to transfer energy from the selected storage unit to charge the string of storage units.

Claim 43

Dependent Claim 48 words

39 . The system of claim 38 , wherein: when the state of charge is less than the target state of charge, the controller directing the non-dissipative load to transfer energy from the string of storage units to charge the selected storage unit until a charge time expires.

Claim 44

Dependent Claim 48 words

40 . The system of claim 38 , wherein: when the state of charge is greater than the target state of charge, the controller directing the non-dissipative load to transfer energy from the selected storage unit to charge the string of storage units until a discharge time expires.

System and method for determining and balancing state of charge among series connected electrical energy storage units

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