Operation of a fuel cell stack to prevent low oxygen concentrations in a surrounding enclosed space

A method of operating a fuel cell stack, the method comprising:

• determining when a vehicle that is powered by the fuel cell stack is in a non-moving state;
• calculating an O2 concentration over time of an assumed enclosed space while the vehicle is in the non-moving state;
• comparing the O2 concentration of the assumed enclosed space over time with a set of O2 concentration concern levels that includes a first O2 concentration concern level and a second O2 concentration concern level, the first O2 concentration concern level being less than a standard atmospheric O2 concentration and the second O2 concentration concern level being less than the first O2 concentration concern level;
• and
• operating the fuel cell stack when the vehicle is in the non-moving state according to a conditional operating mode that includes:
• operating the fuel cell stack without restriction so long as the O2 concentration of the assumed enclosed space remains greater than the first O2 concentration concern level;
• operating the fuel cell stack in a low-power state when the O2 concentration of the assumed enclosed space is equal to or less than the first O2 concentration concern level yet greater than the second O2 concentration concern level;
• and
• shutting down the fuel cell stack when the O2 concentration of the assumed enclosed space is equal to or less than the second O2 concentration concern level.

A method of operating a fuel cell stack, the method comprising:

• determining when a vehicle that is powered by a fuel cell stack is in a non-moving state;
• calculating an O2 concentration over time of an assumed enclosed space that encompasses the vehicle while the vehicle is in the non-moving state;
• comparing the O2 concentration of the assumed enclosed space over time with a set of O2 concentration concern levels that includes a first O2 concentration concern level and a second O2 concentration concern level, the first O2 concentration concern level being less than 21 mol % and greater than 19 mol % and the second O2 concentration concern level being less than 20 mol % and greater than 18 mol %;
• and
• operating the fuel cell stack when the vehicle is in the non-moving state according to a conditional operating mode that includes:
• operating the fuel cell stack without restriction so long as the O2 concentration of the assumed enclosed space remains greater than the first O2 concentration concern level;
• idling the fuel cell stack when the O2 concentration of the assumed enclosed space is equal to or less than the first O2 concentration concern level yet greater than the second O2 concentration concern level;
• and
• shutting down the fuel cell stack when the O2 concentration of the assumed enclosed space is equal to or less than the second O2 concentration concern level.