ESTIMATING MINIMUM VOLTAGE OF FUEL CELLS

• US 20100114513A1
• Filed: 10/31/2008
• Published: 05/06/2010
• Est. Priority Date: 10/31/2008
• Status: Abandoned Application

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Sljivar-Lovria, Sanja, Lakshmanan, Balasubramanian, Zawisa, Michael F., Mallavarapu, Kiran
• Application Number:
  US12/262,592
• Publication Number:
  US 20100114513A1
• Time in Patent Office: Days
• US Class Current: 702/64
• 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 8/0488 of fuel cell stacks
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A method of estimating minimum voltage of fuel cells, and a product using same.

Claims

1. A method comprising:

measuring stack voltage (ν

_S) of a fuel cell stack;

calculating average cell voltage (ν

_C,ave) for the stack;

measuring group voltages of a plurality of groups of fuel cells of the stack;

identifying a group of the plurality of groups having a minimum group voltage (ν

_G,min), which is lower than the measured group voltages of a remainder of the plurality of groups;

calculating a group voltage deviation (Y) for the identified group by multiplying the quantity of fuel cells (N_M) of the identified group by the calculated average cell voltage and then subtracting the measured group voltage of the identified group; and

estimating a minimum cell voltage (ν

_GC,min) of the identified group according to a function wherein;

if Y is less than or equal to a value, then ν

_GC,min equals ν

_G,min minus (N_M−

1)*(ν

_C,ave); and

if Y is greater than the value, then ν

_GC,min equals at least one of ν

_G,min multiplied by a constant or ν

_G,min plus a variable.

2. A method as set forth in claim 1 wherein:

if Y is greater than the value but less than a second value, then ν

_GC,min equals ν

_G,min multiplied by the constant; and

if Y is greater than or equal to second value, then ν

_GC,min equals ν

_G,min multiplied by a second constant.

3. A method as set forth in claim 1 further wherein the constant is about ⅓

.

4. A method as set forth in claim 2 further wherein the second constant is about ⅔

.

5. A method as set forth in claim 1 further wherein the value is about 700 mV.

6. A method as set forth in claim 2 further wherein the second value is about 1400 mV.

7. A method as set forth in claim 2 further wherein the constant is about ⅓

and the second constant is about ⅔

.

8. A method as set forth in claim 7 further wherein the value is about 700 mV and the second value is about 1400 mV.

9. A method as set forth in claim 1 wherein the variable is based on current density.

10. A method as set forth in claim 9 wherein the variable is provided by a lookup table.

11. A method comprising:

identifying a group of a plurality of groups of fuel cells of a fuel cell stack having a minimum group voltage (ν

_G,min), which is lower than any group voltage of a remainder of the plurality of groups;

calculating a group voltage deviation (Y) for the identified group by multiplying the quantity of fuel cells (N_M) of the identified group by an average cell voltage (ν

_C,ave) of the fuel cell stack and then subtracting the minimum group voltage; and

estimating a minimum cell voltage (ν

_GC,min) of the identified group according to a function including a step wherein if Y is less than or equal to a value, then ν

_GC,min equals ν

_G,min minus (N_M−

1)*(ν

_C,ave).

12. A method as set forth in claim 11 wherein the function includes a second step wherein if Y is greater than the value, then ν

_GC,min equals ν

_G,min multiplied by a constant.

13. A method as set forth in claim 12 wherein the second step further provides that if Y is greater than the value but less than a second value, then ν

_GC,min equals ν

_G,min multiplied by the constant.

14. A method as set forth in claim 13 further wherein the constant is about ⅓

.

15. A method as set forth in claim 13 further wherein the value is about 700 mV.

16. A method as set forth in claim 13 wherein the function includes a third step wherein if Y is greater than or equal to second value, then ν

_GC,min equals ν

_G,min multiplied by a second constant.

17. A method as set forth in claim 16 further wherein the second constant is about ⅔

.

18. A method as set forth in claim 16 further wherein the second value is about 1400 mV.

19. A method as set forth in claim 11 wherein the function includes a second step wherein if Y is greater than the value, then ν

_GC,min equals ν

_G,min plus a variable.

20. A method as set forth in claim 19 wherein the variable is based on current density.

21. A product comprising:

a fuel cell stack including a plurality of fuel cells, at least some of which are clustered into a plurality of groups;

a voltage monitoring device coupled to the fuel cell stack to measure stack voltage of the fuel cell stack and group voltages of at least some of the plurality of groups; and

a controller coupled to the voltage monitoring device to;

calculate average cell voltage (ν

_C,ave) for the stack,

identify a group of the plurality of groups having a minimum group voltage (ν

_G,min), which is lower than the measured group voltages of a remainder of the plurality of groups,

calculate a group voltage deviation (Y) for the identified group by multiplying the quantity of fuel cells (N_M) of the identified group by the calculated average cell voltage and then subtracting the measured group voltage of the identified group, and

estimate a minimum cell voltage (ν

_GC,min) of the identified group according to a function wherein;

if Y is less than or equal to a value, then ν

_GC,min equals ν

_G,min minus (N_M−

1)*(ν

_C,ave); and

if Y is greater than the value, then ν

_GC,min equals at least one of ν

_G,min multiplied by a constant or ν

_G,min plus a variable.

22. A product as set forth in claim 21 wherein, according to the function,

if Y is greater than the value but less than a second value, then ν

_GC,min equals ν

_G,min multiplied by the constant; and

if Y is greater than or equal to second value, then ν

_GC,min equals ν

_G,min multiplied by a second constant.

23. A product as set forth in claim 21 wherein the variable is based on current density.

24. A product comprising:

a means for identifying a group of a plurality of groups of fuel cells of a fuel cell stack having a minimum group voltage (ν

_G,min), which is lower than any group voltage of a remainder of the plurality of groups;

a means for calculating a group voltage deviation (Y) for the identified group by multiplying the quantity of fuel cells (N_M) of the identified group by an average cell voltage (ν

_C,ave) of the fuel cell stack and then subtracting the minimum group voltage; and

a means for estimating a minimum cell voltage (ν

_GC,min) of the identified group according to a function including a step wherein if Y is less than or equal to a value, then ν

_GC,min equals ν

_G,min minus (N_M−

1)*(ν

_C,ave).