Method of minimizing the effects of parasitic currents

• US 4,371,825 A
• Filed: 06/04/1981
• Issued: 02/01/1983
• Est. Priority Date: 06/04/1981
• Status: Expired due to Term

• Current Assignee: Energy Development Associates, Inc. (Paramount Global (f/k/a ViacomCBS Inc.))
• Original Assignee: Energy Development Associates, Inc. (Paramount Global (f/k/a ViacomCBS Inc.))
• Inventors: Carr, Peter, Chi, Michael C.
• Primary Examiner(s): Shoop, William M.
• Application Number:
  US06/270,481
• Time in Patent Office: 607 Days
• Field of Search: 307/327, 320/5-8, 320/14, 320/17, 429/123, 429/150
• US Class Current: 320/118
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A method of minimizing the effect of parasitic currents in secondary batteries having a plurality of cells connected electrically in series and a common electrolyte in communication with the cells is described. Specifically, the parasitic currents flowing through the battery cause a cell imbalance over the charge/discharge cycle. This cell imbalance is minimized by first separating the cells of the battery into two equal groups. Then the battery is charged with the two groups of cells connected electrically in series, and subsequently discharged with the two groups of cells reconnected electrically in series in an inverted sequence.

Claims

1. A method of minimizing cell imbalances due to parasitic currents in a secondary electrochemical energy storage device having a plurality of cells formed in two groups with said cells in each of said groups connected electrically in series, and a common electrolyte in communication with each of said cells in said groups of cells, comprising the steps of:

charging said energy storage device with said groups of cells connected electrically in series; and

discharging said energy storage device with said groups of cells reconnected electrically in series in an inverted sequence.

2. The method according to claim 1 wherein the ends of said groups of cells which were connected together during said charging are connected across a load during said discharging, and the ends of said groups of cells which are connected across a source of D.C. electrical power during said charging arc connected together during said discharging.

3. The method according to claim 2 wherein the cells in said groups of cells with the greatest parasitic current losses during said charging have the least parasitic current increases during discharging, and the cells in said group of cells with the least parasitic current losses during said charging have the greatest parasitic current increases during said discharging.

4. The method according to claim 3, wherein said groups of cells each comprise an equal number of cells connected electrically in series.

5. The method according to claim 4 wherein each of said groups of cells further comprise a plurality of cell stacks, each including a plurality of cells connected electrically in series and a positive and negative terminal connected at opposite ends thereof.

6. The method according to claim 5 wherein said cell stacks in each of said groups of cells are connected electrically in series.

7. The method according to claim 6 wherein said cell stacks in each of said groups of cells are connected electrically in parallel.

8. The method according to claim 4 wherein said energy storage device is a secondary battery.

9. The method according to claim 8, wherein said common electrolyte of said secondary battery circulates through said cells.

10. The method according to claim 9, wherein said energy storage device is a metal-halogen battery.

11. The method according to claim 10, wherein said metal-halogen battery is a zinc-chloride battery.

12. A method of minimizing cell imbalances due to parasitic currents in a secondary electrochemical energy storage device having at least a first and second cell stack, each of said cell stacks including a plurality of cells connected electrically in series and a positive and negative terminal connected at opposite ends thereof, and a common electrolyte in communication with each of said cells in said cell stacks, comprising the steps of:

(a) charging said energy storage device with said positive terminal of said first cell stack connected to said negative terminal of said second cell stack; and

(b) discharging said energy storage device with said negative terminal of said first cell stack connected to said positive terminal of said second cell stack.

13. The method according to claim 12 wherein the cells in said stacks with the greatest parasitic current losses during said charging have the least parasitic current increases during said discharging, and the cells in said cell stacks with the least parasitic losses during said charging have the greatest parasitic increases during said discharging.

14. The method according to claim 13 wherein the cells with the greatest parasitic current losses during said charging are the cells nearest said positive terminal of said first cell stack and the cells nearest said negative terminal of said second cell stack.

15. The method according to claim 14 wherein the cells with the least parasitic current losses during said charging are the cells nearest said negative terminal of said first cell stack and the cells nearest said positive terminal of said second cell stack.

16. The method according to claim 15 wherein each of said cell stacks include at least twenty cells connected electrically in series.

17. The method according to claim 16, wherein each of said cell stacks include an equal number of cells connected electrically in series.

18. The method according to claim 17 wherein said energy storage device is a metal-halogen battery.

19. The method according to claim 18 wherein said metal-halogen battery is a zinc-chloride battery.

20. A method of minimizing cell imbalances due to parasitic currents in a secondary electrochemical energy storage device having at least a first and second cell stack, each of said cell stacks including a plurality of cells connected electrically in series and a positive and negative terminal connected at opposite ends thereof, and a common electrolyte in communication with each of said cells in said cell stacks, comprising the steps of:

(a) connecting said cell stacks electrically in series such that said positive end terminal of said first cell stack is connected to said negative end terminal of said second cell stack;

(b) connecting a source of D.C. electrical power across said negative end terminal of said first cell stack and said positive end terminal of said second cell stack, and charging said energy storage device;

(c) disconnecting said source of D.C. electrical power after said energy storage device is charged;

(d) reconnecting said cell stacks electrically in series such that said negative end terminal of said first cell stack is connected to said positive end terminal of said second cell stack; and

(e) connecting a load across said positive end terminal of said first cell stack and said negative end terminal of said second cell stack, and discharging said energy storage device.

21. The method according to claim 20 wherein the cells in said stacks with the greatest parasitic current losses during said charging have the least parasitic current increases during said discharging, and the cells in said cell stacks with the least parasitic losses during said charging have the greatest parasitic increases during said discharging.

22. The method according to claim 21, wherein each of said cell stacks include an equal number of cells connected electrically in series.

23. The method according to claim 22, wherein said energy storage device is a metal-halogen battery.

24. The method according to claim 23 wherein said metal-halogen battery is a zinc-chloride battery.