High-efficiency battery equalization for charging and discharging

• US 9,564,763 B2
• Filed: 10/19/2015
• Issued: 02/07/2017
• Est. Priority Date: 08/28/2009
• Status: Active Grant

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Finberg, Steve, Kishinevsky, Michael
• Primary Examiner(s): Muralidar, Richard V
• Application Number:
  US14/886,802
• Publication Number:
  US 20160043579A1
• Time in Patent Office: 477 Days
• Field of Search: 320118-122
• US Class Current: 1/1
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A non-contiguous group of cells in a battery of cells is selected for charging or discharging the battery.

Claims

1. A method for charging a battery of cells, comprising:

determining a voltage of each of a plurality of cells in the battery;

selecting a subset of the plurality of cells based at least in part on the determined voltages, the subset comprising the N least charged cells, wherein a sum of operating voltages of the N cells is at most equal to a charging voltage;

creating a series connection of cells that includes the subset of the plurality of cells, the series connection of cells excluding at least one cell that requires charging; and

charging the series connection of cells with the charging voltage.

2. The method of claim 1, wherein selecting the subset of the plurality of cells comprises determining at least one of a resting voltage, impedance, or state of charge of each of the plurality of cells.

3. The method of claim 1, wherein the series connection of cells comprises at least two non-adjacent cells.

4. The method of claim 1, wherein the charging voltage for charging the series connection of cells is approximately equal to a multiple of the operating voltage for one of the N cells.

5. The method of claim 1, further comprising modulating the charging voltage with a switching circuit.

6. The method of claim 1, further comprising re-determining, after a delay, the voltage of each of the plurality of cells.

7. The method of claim 6, further comprising selecting, after the delay, a new subset of the plurality of cells.

8. The method of claim 1, further comprising identifying a faulty cell in the battery and bypassing the faulty cell.

9. The method of claim 1, further comprising monitoring, during charging, the voltage of each cell in the series connection of cells.

10. The method of claim 1, wherein cells in the series connection of cells are mismatched and a parameter of each cell deviates, during charging, by less than 1% across the cells.

11. The method of claim 10, wherein the parameter is at least one of resting cell voltage, cell impedance, and percentage of charge.

12. A system for managing charge on cells in a battery, the system comprising:

a voltage-sensing circuit for sensing a voltage across each of a plurality of cells;

a processor for i) selecting a subset of the plurality of cells based at least in part on the sensed voltage of each of the plurality of cells, the subset comprising, in a charging mode, the N least charged cells, wherein a sum of operating voltages of the N cells is at most equal to a charging voltage, and ii) causing the subset of the plurality of cells to be electrically coupled in a series connection of cells, the series connection of cells excluding, in the charging mode, at least one cell that requires charging; and

an output port across the series connection of cells.

13. The system of claim 12, wherein selecting the subset of the plurality of cells is further based on a resting voltage, impedance, or state of charge of each of the plurality of cells.

14. The system of claim 12, wherein the voltage-sensing circuit comprises a voltage sensor local to each cell.

15. The system of claim 12, wherein each of the plurality of cells further comprises circuitry for disabling the cell if the sensed voltage deviates from a threshold.

16. The system of claim 12, wherein each of the plurality of cells further comprises a bypass switch.

17. The system of claim 12, wherein the processor further comprises circuitry for selecting, after a delay, a new subset of the plurality of cells.

18. The system of claim 12, further comprising a pulse-width modulator for adjusting a voltage across the output port.

19. The system of claim 12, wherein the output port is applied to a voltage source for charging the series connection of cells.

20. The system of claim 12, wherein the output port is applied to a load for discharging the series connection of cells.

21. A system for managing charge on cells in a battery, the system comprising:

a plurality of cells, each cell being in parallel with a bypass switch and in series with a cutoff switch;

a voltage-sensing circuit for sensing a voltage across each of the plurality of cells; and

a processor for i) selecting a subset of the plurality of cells based at least in part on the sensed voltages, the subset comprising, in a charging mode, the N least charged cells, wherein a sum of operating voltages of the N cells is at most equal to a charging voltage, and ii) configuring, using the bypass and cutoff switches, a series connection of cells comprising the subset of the plurality of cells, the series connection of cells excluding, in the charging mode, at least one cell that requires charging.