If we are just using it as a generator, a turbine engine makes more sense. Very efficient at fixed rpm. Many trains use that sort of hybrid setup. But if you put in enough battery to warm up a small proane fuel cell to warm up a larger propane fuel cell you could just fill up at the propane pump and still get battery efficiencies but with a lightening tank. And they think they have propane generation from environmental co2 over 90% efficient now too.