Playing exchange map "energy fleet", there are multiple ships with ports, generators, tanks and stuff. I noticed, that ship with tanks doesn't request energy from generator ship, even when tank is almost at 0 and generator is at full.
A ship (1) with a port will not request energy from a ship (2) with a port unless 1 has less energy than 2. This seems to be measured by the flat amount rather than percent full.
Actually, that does look like a bug.
I can vouch for this one too.
It seems that Mines not only take more supply dominance than port modules even if energy production of the mine is less than the energy produced by the mass reactor modules, but on top of that, I guess that reactors are just supplementary energy sources and tanks do not accept reactors that don't share the same ship. (Reactors seem to only supply tanks when the tanks and reactors are on the same ship)