On Demand Fuel Cells (ODFC) is a plugin to support fuel cells that only generate power when it is needed, thereby saving precious fuel. Simulates fuel cells in Kerbal Space Program (KSP), and do a better job of it than stock's use of a resource converter. The main difference is it only generates electricity when it's really needed (batteries almost empty), and otherwise lets electricity of a craft float up and down, as it might in a solar powered vehicle when the sun is eclipsed by another celestial body. It also allows fuel cells to generate byproducts, aimed at supporting life support mods like TACLS.
zer0Kerbal
commented
5 years ago 
want a settings page or just a setting in the settings menu for a difficulty:hard option.
fuel cells will cease to function if the vessel's available EC reaches 0f. This does not include locked tanks.
Additional option is to have an even higher difficulty setting where even if the fuel cell is operational and has fuel it will stall.
A stalled fuel cell is inoperative until it can be jump started.
Reasoning is fuel cells take EC, even if a very small amount, to operate and they cannot operate in a 0 EC environment.