Its another idea of a portable power source for miners. It is also a solution for terraformers.
With a charged crystal you have some power is your hands. So why do you need a stationary power storage block with some diamonds in its body for just discharging a portable power source? Capacity of a temporary MFE is something near useless. An electrolyser is also requires an MFE to be able do recreate some power from cells.
So, I suggest to implemet a power adapter block. It must contain one or more slots for power storage items, some internal power storage (1000 EU is enough) and an internal transformer to lower voltage down. It will be able to discharge power storage items powering connected machines but will not be able to charge anything.
Accepting: Energy Crystals, RE batteries, single-use batteries.
Output: LV. Yes, it's internal transformer is used to generate LV output from crystals.
(W=wooden planks, C=copper cable, T=LV Transformer, S=Circuit, B=RE Battery)
Accepting: Lapotrons, Energy Crystals, RE batteries, single-use batteries.
Output: Pure MV.
(C=copper (or golden?) cable, T=MV transformer, B=RE Battery, A=Advanced circuit, M=Machine block, '.' = empty)