While powering my miners with an MFE I found a little bug:
If you put a charged Bat-Pack in the lower slot of a fully charged MFE, the MFE will output power, without draining energy from the Bat-Pack or its internal storage.
I tested this with 16, 32 and 64 EU/s output and it is not only if you power miners, even linking the output to another MFE works, so you basically have an unlimited 64 EU/s power supply, you just need 120.000EU to start with.
EDIT: Forgot to add I have IC 8.50