Patent ID: 8927165
Filing Date: 2015-01-06
Classification: H01M,Y02E

Abstract:
1. A method for controlling relative humidity (RH) of a fuel cell stack in a fuel cell system, said method comprising: providing an RH sensor on a cathode inlet line that measures the RH of cathode inlet air; using an RH estimation model to determine if the RH sensor is providing a valid RH signal at fuel cell system start-up; using the RH estimation model to determine if the RH sensor is providing a valid RH signal during a run mode of the fuel cell system; calculating an average of the RH signal over a predetermined time period, which is determined by the sensing signal characteristics of the RH sensor, if the RH sensor is providing a valid RH signal during the run mode of the fuel cell system; using the calculated average of the RH signal if the RH sensor becomes invalid during the run mode to enable the fuel cell stack to operate utilizing closed-loop cathode inlet RH control; operating the fuel cell stack at a predetermined optimized stack power level for a predetermined period of time if the RH signal is invalid at system start-up, wherein the optimized stack power level provides a highest stack relative humidity without liquid water occurring inside the stack; and operating the fuel cell stack with closed-loop cathode inlet RH control using the highest stack relative humidity after the predetermined period of time has expired.