NOVELTY - Fuel cell stack (112) has bipolar plate assembly (110) having active feed region (114) with nested bipolar plates defining cathode and anode side flow channels; and inactive feed region (116, 118) with non-nested bipolar plates defining cathode and anode side flow channels. The cathode and anode side flow channels in the inactive feed region are connected with, and are the same size as, the cathode and anode side channels in the active feed region, respectively. The non-nested bipolar plates of the inactive feed region of the bipolar plate assembly are non-bonded with respect to each other.    USE - The fuel cell stack is used as a power source in many applications, e.g. for use in electrical vehicular power plants to replace internal combustion engines.    ADVANTAGE - The clearance gaps in the inactive feed regions of the fuel cell stack are controlled by non-bonded, non-nested bipolar plates to provide reactant flow uniformity and pressure within fuel cells and fuel cell stacks utilizing nested bipolar plates in the active feed regions and non-nested bipolar plates in the inactive feed regions. The clearance gaps in the coolant channels in the inactive feed regions of each fuel cell have nested active feed regions providing reactant flow uniformity and pressure within fuel cells and fuel cell stacks since coolant pressure drop is less sensitive to variations of clearance gap heights in the inactive feed regions than the reactant flow pressure drops in the inactive feed regions.    DETAILED DESCRIPTION - Fuel cell stack comprises a bi-polar plate assembly. An active feed region includes a stack of fuel cells. Each fuel cell includes a membrane electrode assembly having a cathode side and an anode side, a cathode side diffusion media layer on the cathode side of the membrane electrode assembly, an anode side diffusion media layer on the anode side of the membrane electrode assembly, and an active feed region of the bipolar plate assembly positioned between opposing diffusion media layers in adjacent fuel cells. The active feed region of the bipolar plate assembly includes nested bipolar plates defining cathode side flow channels and anode side flow channels. An inactive feed region includes a stack of membranes that form part of each membrane electrode assembly in the stack of fuel cells and an inactive feed region of the bipolar plate assembly. The inactive feed region of the bipolar plate assembly includes non-nested bipolar plates defining cathode side flow channels and anode side flow channels. The cathode side flow channels in the inactive feed region are connected with, and are the same size as, the cathode side channels in the active feed region. The anode side flow channels in the inactive feed region are connected with, and are the same size as, the anode side flow channels in the active feed region. The fuel cells are free of diffusion media layers in the inactive feed region. The non-nested bipolar plates of the inactive feed region of the bipolar plate assembly are mutually non-bonded with respect to each other.    An INDEPENDENT CLAIM is included for controlling clearance gaps in inactive feed regions of a fuel cell stack.    DESCRIPTION OF DRAWING(S) - The figure is a top view of a plate in a fuel cell stack.    Bipolar plate assembly (110)    Fuel cell stack (112)    Active feed region (114)    Inactive feed region (116, 118)