Hello i came across another possible issue:
I was running out of space in my temporary home and placed my crystalcharger against the wall. Right above it i placed a generator to charge my batterys. There was no cable to the crystalcharger as i did not intend to use it soon.
I put coal in the generator to charge my batterys thinking of not much, but as i came back i noticed the generator kept on burning coal.
There was no item in the charger, the "lightning" for energy did not increase any at all, even after 30 coal, but the generator kept on burning it.
*edit*
After further use of the crystalcharger i noticed the following:
Crystals can be put in stacked. Crystals will be charged. Crystals wont stack on the output end.
I am not sure if they are spilled out like batteries but i know i put 3 crystals in and had only 1 in the output. I would have tested more but ran out of crystals ^^.
(there was no chest close either, does it even work with the crystalcharger?)
this was an experience with the smp version.