Patent ID: 7887960

Claim:
A method of operating an electrochemical conversion assembly comprising a plurality of electrochemical conversion cells arranged in a conductively coupled fuel cell stack, wherein respective ones of said cells comprise membrane electrode assemblies positioned between first and second reactant flowfields and said membrane electrode assemblies comprise a proton exchange membrane, said method comprising: initiating operation of said fuel cell stack according to an initial set of operating parameters comprising hydration, wherein said operation of said fuel cell stack runs through a plurality of operational cycles characterized by changes in humidification, of said membrane electrode assemblies; extracting cyclic stress data representative of said plurality of operational cycles; determining a life spent value L X representing stack life expended over said plurality of operational cycles, wherein said life spent value L X is a function of fatigue life data of the fuel cell stack and a stress histogram that is derived from said cyclic stress data arising from said cyclic stress imparted upon said membrane electrode assembly over said plurality of operational cycles; determining an actual usage value L U representing a number of said operational cycles executed from initiation of said fuel cell stack operation, wherein said actual usage value L U is substantially independent of stress imparted upon said membrane electrode assembly over said plurality of operational cycles; comparing said life spent value L X to said actual usage value L U ; and controlling at least one operating parameter comprising hydration of said electrochemical conversion assembly as a function of said comparison of said life spent value L X to said actual usage value L U .