A stack (11) of fuel cells have water flow channels receiving water through a pump (33) from an accumulator (29) having double walls (63, 66) with vacuum insulation panels (VIPs) (65, 68) therebetween, auxiliary DC power source (80) (battery or supercapacitor) is disposed in a container (43) having double walls (81, 86) with VIPs (65, 68) encapsulated therebetween. A keep-warm heater (51) keeps the source warm enough for at least half power capacity, the source driving its own heater as well as a keep-warm heater (50) in the accumulator to keep the accumulator above freezing. A microwave heater (58) disposed in the accumulator distributes energy to melt ice using fuel cell stack power upon startup.