Many player think that current energy cell texture doesn't look good in the 1.12 world.
So, you should replace it.

We've retextured most of the AE2 blocks and parts to match the modern counterparts while trying to not stray too far from the original style. That's the design choice moving forward.

We're aware, however, that not everyone agrees with the changes, so you're free to install https://github.com/AE2-UEL/ProgrammerArt as a resource pack!