Method and apparatus for monitoring fuel cell voltages

• US 20040150405A1
• Filed: 12/03/2003
• Published: 08/05/2004
• Est. Priority Date: 12/03/2002
• Status: Active Grant

• Current Assignee: Hydrogenics Corporation (Cummins Incorporated)
• Original Assignee: Hydrogenics Corporation (Cummins Incorporated)
• Inventors: Masse, Stephane, Burany, Stephen, Gopal, Ravi B., Freeman, Norman A.
• Granted Patent: US 7,148,654 B2
• Time in Patent Office: Days
• US Class Current: 324/426
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: H01M 8/04552 of the individual fuel cell
• CPC Class Codes: H01M 8/04559 of fuel cell stacks
• CPC Class Codes: H01M 8/04753 of fuel cell reactants
• CPC Class Codes: H01M 8/04955 Shut-off or shut-down of fuel cells
• CPC Class Codes: H01M 8/04992 characterised by the implementation of mathematical or computational algorithms, e.g. feedback control loops, fuzzy logic, neural networks or artificial intelligence
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A system and method for monitoring cell voltages for a plurality of electrochemical cells connected in series forming a cell stack. The method includes dividing the cells into at least two cell groups, measuring the voltage across each cell group and estimating the minimum cell voltage for each group based on the average cell stack voltage and an estimated number of deficient cells in each group. The lowest minimum cell voltage for the entire cell stack is then determined.

Claims

1. A method for monitoring cell voltages for a plurality of electrochemical cells connected in series forming a cell stack, the method comprising:

a) dividing the plurality of electrochemical cells into at least two cell groups;

b) determining an average cell stack voltage V_sa;

c) measuring a cell group voltage V_g for each cell group;

d) estimating a minimum cell voltage V_mi for each cell group to obtain a set of minimum cell voltages; and

,

e) determining a minimum cell voltage V_min for the cell stack by finding the minimum value in the set of minimum cell voltages.

2. A method as claimed in claim 1, wherein the minimum cell voltage for one of the cell groups is estimated according to

3. A method as claimed in claim 2, wherein the method further comprises:

f) activating an alarm when the minimum cell voltage V_min for the cell stack is equal to or less than a first threshold value.

4. A method as claimed in claim 2, wherein the method further comprises:

f) shutting down the cell stack when the minimum cell voltage V_min for the cell stack is equal to or less than a second threshold value.

5. A method as claimed in claim 2, wherein the number of cells N in the cell group is 4.

6. A method as claimed in claim 2, wherein the estimated number of cells M operating below the average cell stack voltage is 1.

7. A method as claimed in claim 3, wherein the first threshold value is 0.5 V.

8. A method as claimed in claim 4, wherein the second threshold value is 0.3 V.

9. A voltage monitoring system for monitoring cell voltages for a plurality of electrochemical cells connected in series forming a cell stack, the plurality of cell groups being divided into at least two cell groups, the voltage monitoring system comprising:

a) a voltage measuring unit for measuring a cell group voltage V_g for each cell group, and cell a stack voltage V_s for the cell stack; and

,

b) a processing means connected to the voltage measuring unit for calculating an average cell stack voltage V_sa, estimating a cell group minimum cell voltage V_mi for each cell group to obtain a set of minimum cell voltages, and determining a minimum cell voltage V_min for the cell stack by finding the minimum value in the set of minimum cell voltages.

10. A voltage monitoring system as claimed in claim 9, wherein the processing means estimates the minimum cell voltage for one of the cell groups according to

11. A voltage monitoring system as claimed in claim 10, wherein the processing means activates an alarm when the minimum cell voltage V_min for the cell stack is equal to or less than a first threshold value.

12. A voltage monitoring system as claimed in claim 10, wherein the processing means shuts down the cell stack when the minimum cell voltage V_min for the cell stack is equal to or less than a second threshold value.

13. A voltage monitoring system as claimed in claim 10, wherein the number of cells N in the cell group is 4.

14. A voltage monitoring system as claimed in claim 10, wherein the estimated number of cells M operating below the average cell stack voltage is 1.

15. A voltage monitoring system as claimed in claim 11, wherein the first threshold value is 0.5 V.

16. A voltage monitoring system as claimed in claim 12, wherein the second threshold value is 0.3 V.

17. A method for monitoring cell voltages for a plurality of electrochemical cells connected in series forming a cell stack, the method comprising:

a) dividing the plurality of electrochemical cells into at least two cell groups;

b) determining an average cell stack voltage V_sa;

c) measuring a cell group voltage V_g for one of the cell groups;

d) estimating a minimum cell voltage V_mi for the one of the cell groups;

e) comparing the minimum cell voltage V_mi to a threshold value; and

,

f) repeating steps c, d and e until one of the minimum cell voltages V_mi is less than or equal to the threshold value or the minimum cell voltage for each of the cell groups has been estimated.

18. A method as claimed in claim 17, wherein minimum cell voltage for one of the cell groups is estimated according to

19. A method as claimed in claim 17, wherein the method further comprises:

g) activating an alarm when the minimum cell voltage V_min for the cell stack is equal to or less than the threshold value.

20. A method as claimed in claim 17, wherein the method further comprises:

g) shutting down the cell stack when the minimum cell voltage V_min for the cell stack is equal to or less than the threshold value.

21. A method as claimed in claim 18, wherein the number of cells N in the cell group is 4.

22. A method as claimed in claim 18, wherein the estimated number of cells M operating below the average cell stack voltage is 1.

23. A method as claimed in claim 19, wherein the threshold value is 0.5 V.

24. A method as claimed in claim 20, wherein the threshold value is 0.3 V.

25. A voltage monitoring system for monitoring cell voltages for a plurality of electrochemical cells connected in series forming a cell stack, the plurality of cell groups being divided into at least two cell groups, the voltage monitoring system comprising:

a) a voltage measuring unit for measuring a cell group voltage V_g for each cell group, and cell a stack voltage V_s for the cell stack; and

,

b) a processing means connected to the voltage measuring unit for calculating an average cell stack voltage V_sa, repeatedly estimating a cell group minimum cell voltage V_mi for one of the cell groups and comparing the minimum cell voltage V_mi to a threshold value until one of the minimum cell voltages V_mi is less than or equal to the threshold value or the minimum cell voltage V_mi for each of the cell groups has been estimated.

26. A voltage monitoring system as claimed in claim 25, wherein the processing means estimates the minimum cell voltage for one of the cell groups according to

27. A voltage monitoring system as claimed in claim 25, wherein the processing means activates an alarm when the minimum cell voltage V_min for the cell stack is equal to or less than the threshold value.

28. A voltage monitoring system as claimed in claim 25, wherein the processing means shuts down the cell stack when the minimum cell voltage V_min for the cell stack is equal to or less than the threshold value.

29. A voltage monitoring system as claimed in claim 26, wherein the number of cells N in the cell group is 4.

30. A voltage monitoring system as claimed in claim 26, wherein the estimated number of cells M operating below the average cell stack voltage is 1.

31. A voltage monitoring system as claimed in claim 27, wherein the threshold value is 0.5 V.

32. A voltage monitoring system as claimed in claim 28, wherein the threshold value is 0.3 V.