Description of the issue:

When trying to input FE into a battery box from the mod electrodynamics (which is able to convert to it's native power type of joules), the connector empties its stored buffer of energy (256FE) into the battery box and then refuses to collect any more energy from the power source. No such issue is experienced however when extracting energy from a battery box back into and Immersive Engineering accumulator.

Crashlog:

N/A

Versions & Modlist

Forge: 39.0.59
IE: 1.18.1-7.1.0-145
Electrodynamics: 1.18.1-0.5.9-0

Modlist:
https://gist.github.com/SheriffEllis/b496baa3f979df625c41d71e7d28222a
(optifine was installed during my demonstration but the issue persists without it)

I did a test using the connectors from create: crafts and additions mod. Inputting FE into the battery box from Electrodynamics has no issues when inputting FE using said connectors.

IE's connectors are a push based system. The connector you put on the battery box will never have had power in it, but some power seems to have gone through it.

As for why it only lets a little bit through and then nothing more? No idea!
Please try with some other Forge Energy mod and see if they have the same issue. I have no reason to believe that this is caused by IE.