Abstract: Electrolyte is replenished in a fully assembled stack of fuel cells by depositing dilute electrolyte of known concentration on an external vertical face of the stack. The electrolyte is absorbed into the cell components through their edges by capillary action. Electrolyte is continuously deposited on the stack surface until the electrodes and matrix layers of the stack are fully saturated. Thereafter the stack is heated and water is evaporated until the stack has a desired operable electrolyte volume and electrolyte concentration therein. By knowing the total volume of electrolyte in the stack when the stack is fully saturated, and by knowing the concentration of the electrolyte in the fully saturated stack, the conditions under which water is thereafter evaporated may be controlled to result in the desired electrolyte volume and electrolyte concentration within the stack.

Abstract: A manifold-to-stack seal and sealing method for fuel cell stacks. This seal system solves the problem of maintaining a low leak rate manifold seal as the fuel cell stack undergoes compressive creep. The seal system eliminates the problem of the manifold-to-stack seal sliding against the rough stack surface as the stack becomes shorter because of cell creep, which relative motion destroys the seal. The seal system described herein utilizes a polymer seal frame firmly clamped between the manifold and the stack such that the seal frame moves with the stack. Thus, as the stack creeps, the seal frame creeps with it, and there is no sliding at the rough, tough to seal, stack-to-seal frame interface. Here the sliding is on a smooth easy to seal location between the seal frame and the manifold.

Abstract: A manifold-to-stack seal and sealing method for fuel cell stacks. This seal system solves the problem of maintaining a low leak rate manifold seal as the fuel cell stack undergoes compressive creep. The seal system eliminates the problem of the manifold-to-stack seal sliding against the rough stack surface as the stack becomes shorter because of cell creep, which relative motion destroys the seal. The seal system described herein utilizes a polymer seal frame firmly clamped between the manifold and the stack such that the seal frame moves with the stack. Thus, as the stack creeps, the seal frame creeps with it, and there is no sliding at the rough, tough to seal, stack-to-seal frame interface. Here the sliding is on a smooth easy to seal location between the seal frame and the manifold.

Abstract: An electrolyte reservoir layer disposed behind and adjacent one of the catalyst layers of a fuel cell is a porous, hydrophilic material. Excess liquid volume wicks into the reservoir layer through the catalyst layer and fills the smaller pores within the reservoir. The larger pores remain empty and provide clear passageways for the reactant gas to reach the catalyst. Wetproofing of the reservoir layer is not required. In a preferred embodiment the reservoir layer is the electrode substrate whereby the catalyst layer is bonded to the surface thereof.

Abstract: A cooler for removing waste heat from a stack of fuel cells uses a non-dielectric coolant which is carried in a plurality of tubes passing through one or more separator plates in the stack. Preferably the coolant is water so that heat removal is by evaporation of the water within the tubes by boiling. The tubes are electrically insulated from the cells by a coating of dielectric material such as polytetrafluoroethylene. In one embodiment of the present invention the cooler tubes are connected to the stack coolant supply conduits by dielectric hoses having a high length to diameter ratio to provide a several hundred thousand ohm impedance path in case of a flaw in the protective dielectric coating, in order that a short circuit of the stack does not occur.

Abstract: A fuel cell coolant system for use with a plurality of fuel cell stacks connected electrically in series is adapted to use a non-dielectric coolant carried through each stack by electrically conductive tubes. Each stack also includes a plenum for distributing coolant to the tubes. To prevent short circuits across the stacks due to shunt currents in the coolant the plenums are electrically insulated from a grounded main coolant supply line, such as by dielectric hose connections, and each plenum is electrically connected to one end of its respective stack. By this invention the maximum driving potential for any shunt current is the potential drop across a stack rather than the potential drop from a stack to ground. In a preferred embodiment dielectric hoses are used to connect the plenums to the tubes in order to prevent short circuiting across cells within a stack.