So normally i dont really need to, i have the ability to use Solar Arrays most of the time, and have battery power in reserve to do what i need to do. But i started a new project this weekend and fuel cells are the best option for it, which leads me to my question. Is there a way to only turn on fuel cells when you need them? Like when the battery gets below a certain point? Im trying to build an aircraft to fly around Kerbin, non stop on only solar power and just a small amount of fuel. So far, during the day i can rely mostly on solar power, but after some time my fuel cells need to kick on. The issue is, that my fuel cells are running continuously and it's costing me fuel during flight, fuel that i will need on the dark side of the planet. Thank you for any assistance.
