Patent Application

App. No. 12/262,592

Abstract

Claims (51)

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 ).

Assignments (12)