METHOD FOR BALANCING CELLS IN BATTERIES

• US 20130057198A1
• Filed: 08/16/2012
• Published: 03/07/2013
• Est. Priority Date: 09/02/2011
• Status: Active Grant

• Current Assignee: Boston-Power Inc.
• Original Assignee: Boston-Power Inc.
• Inventors: Gerlovin, Mark
• Granted Patent: US 9,166,416 B2
• Time in Patent Office: Days
• US Class Current: 320/103
• CPC Class Codes: H02J 1/12 Parallel operation of dc generators with converters, e.g. with mercury-arc rectifier
• CPC Class Codes: H02J 7/0019 using switched or multiplexed charge circuits
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

Adjacent battery cells connected in devices are balanced by closing a first circuit to charge an energy storage device from a first battery cell and thereafter simultaneously opening the first isolated switch and closing a second isolated switch to cause the energy storage device to charge a second battery cell. A circuit includes an isolated switch that operates simultaneously to balance battery cells connected in series, and a battery system balances battery modules connected in series, the battery module including battery cells connected in series. The battery cells and modules can be balanced by hierarchical balancing of modules of the battery pack and component cells of the modules.

Claims

1. A method for balancing two adjacent battery cells arranged in series, comprising the steps of:

a) closing a first isolated switch of a first battery cell from which energy is to be transferred to thereby transfer energy for that battery to an energy storage device that is in electrical communication with a node connecting the negative terminal of a second battery cell to a positive terminal of the first battery cell, thereby charging the energy storage device; and

b) simultaneously opening the first isolated switch and closing a second isolated switch, the second isolated switch thereby causing energy to be transferred from the energy storage device to the second cell, whereby the second battery cell will have a voltage at least closer to that of the first battery cell.

2. The method of claim 1, wherein the energy transfer is to and from an energy storage device that is an inductor.

3. The method of claim 1, wherein the first and second isolated switches are at least one member selected from the group consisting of an opto-isolated switch, a magnetic-isolated switch, and a capacitive-isolated switch.

4. The method of claim 1, wherein the first and second isolated switches are opto-isolated switches.

5. The method of claim 4, wherein the opto-isolated switches are active opto-isolated switches.

6. A circuit for transferring energy between cells in a battery, comprising:

a) a first node;

b) a second node;

c) a first isolated switch connecting the first and second nodes, the first and second nodes connectable to respective terminals of a first battery cell;

d) a third node;

e) a second isolated switch connecting the second node and the third node, the second and third nodes connectable to respective terminals of a second battery cell;

f) an energy storage device connected to the second node; and

g) a control unit configured to operate the first and second switches to transfer energy from the first battery cell to the second battery cell via the energy storage device, the control unit opening the first switch concurrently with closing the first switch to transfer energy from the energy storage device to the second battery cell.

7. The method of claim 6, wherein the energy storage device is an inductor.

8. The method of claim 6, wherein the first and second isolated switches are at least one member selected from the group consisting of an opto-isolated switch, a magnetic-isolated switch, and a capacitive-isolated switch.

9. The method of claim 6, wherein the first and second isolated switches are opto-isolated switches.

10. The method of claim 9, wherein the opto-isolated switches are active opto-isolated switches.

11. The circuit of claim 10, wherein the first and second opto-isolated switches are powered by a node at a terminal of one of the first and second battery cells.

12. The circuit of claim 11, further comprising a DC-DC boost converter, the first and second isolated switches being powered by the DC-DC boost converter.

13. The circuit of claim 6, wherein the energy storage device is an inductor.

14. A battery system comprising:

a) a plurality of battery modules, each module including;

i) a string of battery cells, and

ii) a plurality of cell balancing circuits, each of the plurality of cell balancing circuits including a pair of switches and a control unit configured to operate the pair of switches to transfer energy between two adjacent cells in the string of battery cells; and

b) a plurality of module balancing circuits, each of the plurality of module balancing blocks including a pair of switches and a control unit configured to operate the pair of switches to transfer energy between two adjacent modules.

15. The battery system of claim 14, wherein the pair of switches at each of the cell balancing circuits is a pair of isolated switches.

16. The method of claim 14, wherein the first and second isolated switches are at least one member selected from the group consisting of an opto-isolated switch, a magnetic-isolated switch, and a capacitive-isolated switch.

17. The method of claim 14, wherein the first and second isolated switches are opto-isolated switches.

18. The method of claim 14, wherein the opto-isolated switches are active opto-isolated switches.

19. The battery system of claim 14, wherein at least one of the pairs of switches are powered through a node at a terminal of one of the first and second battery cells.

20. The circuit of claim 14, further comprising a DC-DC boost converter connected to the respective nodes of at least one cell and to switch corresponding tot hat cell, whereby the DC-DC boost converter can power that switch.

21. The circuit of claim 14, wherein each of the cell balancing circuits includes an energy storage device for storing energy during an energy transfer between the two adjacent cells.

22. The circuit of claim 21, wherein the energy storage device is an inductor.

23. A method of hierarchical balancing of a plurality of battery modules, comprising:

a) balancing cells of a first battery module;

b) balancing cells of a second battery module; and

c) balancing the modules, including the steps of;

closing a first circuit of the first battery module from which energy is to be transferred to thereby transfer energy for that battery module to an energy storage device that is in electrical communication with a node connecting the negative terminal of the second battery module to a positive terminal of the first battery module, thereby charging the energy storage device; and

simultaneously opening the first circuit and closing a second circuit, the second circuit thereby causing energy to be transferred from the energy storage device to the second battery module, whereby the second battery module will have a voltage at least closer to that of the first battery module.

24. A method for balancing battery modules, comprising the steps of:

a) closing a first circuit of a first battery module from which energy is to be transferred to thereby transfer energy for that battery module to an energy storage device that is in electrical communication with a node connecting the negative terminal of a second battery module to a positive terminal of the first battery module, thereby charging the energy storage device; and

b) simultaneously opening the first circuit and closing a second circuit, the second circuit thereby causing energy to be transferred from the energy storage device to the second battery module, whereby the second battery module will have a voltage at least closer to that of the first battery module.

25. The method of claim 24, wherein he circuits of the first and second battery modules are closed and opened by opto-isolated switches.

26. The circuit of claim 24, wherein the first and second opto-isolated switches are powered by a node at a terminal of one of the first and second battery cells.

27. The circuit of claim 26, further comprising a DC-DC boost converter, the first and second opto-isolated switches being powered by the DC-DC boost converter.

28. A method of balancing battery cells, comprising:

detecting an energy imbalance between a first battery module and a second battery module, each of the modules including a plurality of battery cells;

transferring energy from the first battery module to the second battery module such that the second battery module will have a voltage at least closer to that of the first battery module;

detecting an energy imbalance between a first battery cell and a second battery cell of the second battery module upon distributing the energy from the first module among the battery cells of the second module; and

transferring energy from the first battery cell to the second battery cell such that the second battery cell will have a voltage at least closer to that of the first battery cell.

29. The method of claim 28, wherein transferring energy from the first battery cell to the second battery cell includes the steps of:

a) closing a first isolated switch of a first battery cell from which energy is to be transferred to thereby transfer energy for that battery to an energy storage device that is in electrical communication with a node connecting the negative terminal of a second battery cell to a positive terminal of the first battery cell, thereby charging the energy storage device; and

b) simultaneously opening the first isolated switch and closing a second isolated switch, the second isolated switch thereby causing energy to be transferred from the energy storage device to the second cell, whereby the second battery cell will have a voltage at least closer to that of the first battery cell.

30. The method of claim 29, wherein the first and second isolated switches are at least one member selected from the group consisting of an opto-isolated switch, a magnetic-isolated switch, and a capacitive-isolated switch.

31. The method of claim 29, wherein the first and second isolated switches are opto-isolated switches.

32. The method of claim 31, wherein the opto-isolated switches are active opto-isolated switches.

33. The method of claim 28, further comprising detecting a fault at a cell-balancing circuit in the second module, the fault preventing energy transfer between the second battery cell and a third battery cell.

34. The method of claim 33, further comprising transferring energy from a fourth battery cell to the third battery cell such that the third battery cell will have a voltage at least closer to that of the fourth battery cell.