Fuel cell stack health monitoring using groups of fuel cells

A fuel cell propulsion system comprising a controller, a fuel cell stack, one or more valves, and one or more fuel storage vessels wherein:

• the one or more valves fluidly couple the one or more fuel storage vessels to the fuel cell stack;
• each fuel storage vessel stores either a reactant or air;
• the fuel cell stack comprises a plurality of cell groups;
• each cell group comprises a plurality of fuel cells and a group sensor;
• the group sensor measures one or more electrical characteristics of the respective cell group;
• the controller comprises one or more processors and memory;
• the controller is communicatively coupled to each group sensor;
• and
• the one or more processors execute machine readable instructions to
• compare a measured electrical characteristic to one or more thresholds stored in memory, and
• actuate the one or more valves to adjust a flow of reactant or air from the fuel storage vessels to the fuel cell stack when the comparison indicates a non-systemic event.