Abstract: A fuel cell stack including a bypass is provided. The fuel cell stack includes a plurality of electricity generating cells in the known manner. A bypass is included for reducing the water entering the electricity generating cells of the fuel cell stack. The bypass may comprise at least one bypass cell disposed adjacent the first electricity generating cell in the stack. The bypass cell comprises a pair of separator plates defining an anode side and a cathode side. The bypass cell includes a conductive spacer comprising gas diffusion media disposed between the pair of separator plates. The bypass cell preferably blocks the cathode port on the separator plate. In this manner, the cell is inactive and does not produce electricity. The anode port of the cell remains open and an anode feed flows through the bypass to reduce water provided to the first electricity-generating cell. Alternatively or additionally, the cathode port remains open. Further the bypass may be placed before the cell stack itself.

Abstract: A system and method for controlling an electrochemical conversion assembly are provided. The system is configured such that operation of one or both of the second reactant supply and the temperature controller responds to the cathode-side RH signal to a degree sufficient to maintain relative humidity within the second flowfield portion within a suitable humidification range. The suitable humidification range is a function of the degree to which the vapor barrier layers inhibit the migration of water molecules from the membrane electrode assembly.

Abstract: A non-functional fuel cell for a fuel cell stack includes a shim disposed between gas diffusion media, a bipolar plate at one end, and either a bipolar plate or a unipolar plate at the other end. The shim of the non-functional cell replaces the membrane electrode assembly (MEA) in a normal fuel cell located in the middle or the end of the fuel cell stack. The shim is coated with electrically conductive, corrosion-resistant protective coating. The shim may be cleaned prior to applying the protective coating to remove an oxide layer from the surface of the shim. The non-functional fuel cell may be included in the initial design of the fuel cell stack, or may be used to replace one or more damaged or inoperative fuel cells to increase the overall performance of the fuel cell stack.