I think I've run into a minor bug with the K&K Fuelcell Container. Despite having enough fuel on my base, activating the fuelcell just gets a "Output capped at 95%" message.
I did a quick test using a rover using the FUR roof mounted fuelcell and that works fine as you can see here. The K&K fuelcell does nothing and doesn't use any resources but the roof mounted fuelcell works perfectly.