If you have a NeoTech RF battery and an activated single/double/triple/quadruple/quintuple battery, and there's power in either of them, they will establish a positive feedback loop that will drain the NeoTech battery and charge the AA battery to capacity, along with any other items in your inventory that can accept power.

"positive feedback loop" = you have more power in the end than what you started with?

Exactly.

I'm presuming the NeoTech battery can also charge other RF holding items?
Please try if this happens with only two NeoTech batteries or with only two Actually Additions batteries.

Just checked, NeoTech batteries don't seem to charge each other. They do, however, charge other RF-enabled devices anywhere in your inventory, assuming they're compatible (i.e., not EnderIO.)

Please ask the NeoTech dev about this. Actually Additions batteries don't create a loop when charging each other, so I suspect that this is an issue with NeoTech's battery implementation.

Couldn't you just blacklist the NeoTech batteries altogether? Just out of curiosity. ALso, I forgot to say, I installed TESLA to make AA batteries compatible with EIO items. So, that might have a bearing on the current situation.

No, I can't just blacklist them because that would be ignoring and not fixing the issue. I'd rather not do that.

That's a fair point. I'm reporting it now.

EDIT I was about to give you the link, but I got ninja'd by GitHub.