Fuel cell assemblies (25) incorporating apparatus for use with existing electrolyte passage means for replenishing electrolyte within fuel cell stacks of a fuel cell stack module to keep the matrices in the optimum electrolyte-wetted condition. Pump means (82) is provided to withdraw a predetermined volume of electrolyte from electrolyte reservoir means (106) and propel it in a series of pulses of predetermined duration through transfer means (90) to distribution means (92) which divides the electrolyte volume into streams according to the number of fuel cell stacks in the module. Each portion of the electrolyte volume is then introduced into existing electrolyte passage means (102). The pulses of electrolyte must be of a sufficiently short duration that no electrolyte streams are still issuing within distribution means when electrolyte has reached electrolyte passage means of the fuel cell stacks.
