When connecting machines to a energy cube, it get's drained even if the machines internal cache is full.

In my setup i have a solar farm that constantly provides the energy cube with energy...

Tested a bit more. Seems like it's Resondant Inductions cables that is causing the issue. But may this be a bug in Resondant Induction or Mekanism?

Most likely because the machine is operating. If this is not the case, I am unable to reproduce.

It's definitely a Resonant Induction bug - something similar to this was posted just yesterday.

Ok, i can now confirm that Energy Cubes work just fine with Mekanism's electrical cables.