NOVELTY - Fuel cell system (100) comprises: (A) (a) a fuel cell stack having many fuel cells (112), where the fuel cell stack (110) includes anode supply manifold (118) and anode exhaust manifold (120), (b) a sensor for measuring at least one of environmental condition affecting fuel cell stack or a characteristic of fuel cell stack, where the sensor generates sensor signal representing measurement of sensor, and (c) a processor for receiving the sensor signal, analyzing the sensor signal and controlling flow rate of fluid flowing into anode supply manifold based upon analyzed sensor signal.    USE - The fuel cell system is useful in vehicles.    ADVANTAGE - The fuel cell system: minimizes anode fill time and degradation of the fuel cell system due to a start-up procedure; and provides basis to tune and modify the fuel cell start-up to maximize efficiency, durability and reliability of the fuel cell system.    DETAILED DESCRIPTION - Fuel cell system (100) comprises either: (A) (a) a fuel cell stack (110) having many fuel cells (112), where the fuel cell stack includes an anode supply manifold (118) and an anode exhaust manifold (120), (b) a sensor for measuring at least one of an environmental condition affecting the fuel cell stack or a characteristic of the fuel cell stack, where the sensor generates a sensor signal representing a measurement of the sensor, and (c) a processor for receiving the sensor signal, analyzing the sensor signal and controlling a flow rate of a fluid flowing into the anode supply manifold based upon the analyzed sensor signal; or (B) (a) as above per se, (b1) a sensor for measuring at least one of a volume of fluid injected into the anode supply manifold, a voltage across at least one fuel cell, a current supplied from the fuel cell stack, a shut-down time period, or an environmental factor, where the sensor generates a sensor signal representing a measurement of the sensor, and (c) as above per se. An INDEPENDENT CLAIM is also included for controlling a flow rate of a fluid in a fuel cell system, comprising: providing a fuel cell stack having many fuel cells, where the fuel cell stack includes an anode supply manifold and an anode exhaust manifold; measuring at least one of an environmental condition affecting the fuel cell stack or a characteristic of the fuel cell stack; and controlling a flow rate of a fluid flowing into the anode supply manifold based upon an analysis of at least one of the environmental condition measured or the characteristic of the fuel cell stack measured.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic cross-sectional elevational view of a fuel cell system.    Fuel cell system (100)    Fuel cell stack (110)    Fuel cells (112)    Anode supply manifold (118)    Anode exhaust manifold (120)