I might be wrong, but I think I found a bug. I placed a PESD in a PESU. Got like 50 million eu put in to it. Here is the Setup i used PESU -> IV Tranformer -> HV Transformer -> MFSU. Charged to a bit over 3 million eu then looked at the PESU and it was empty! There is no way the loss should be this high. But I am running IC2 version 1.115 so that might have something to do with it.
That has to do with the way Transformers work.
Since they can only convert one Packet per tick and the IV transformer makes 16 EV packets from 1 IV packet, it should be like this:
PESU>IV transformer> wire connecting to 16 different HV transformers> wire connecting to MFSU.
If you don't want to use so many transformers connect a wire back to the PESU from the IV transformer. This way it will only give off 2048 EU per tick.