system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do some batteries "re-charge" themselves a little bit after they already died and you wait for a while?
gpt
Batteries create electrical charge off of a chemical reaction occurring within the case. However as the reactants are not gaseous, it is very hard (teetering on impossible) to react all of the stuff together on the first go. Meaning, if you mix two liquid reactants together by pouring one into another, it is impossible to tell when the reaction is fully finished and there could be "holdouts" or clumps of reactants that have yet to come into contact with anything to react with.

Batteries "regain" charge because there is still some holdout reactants within the case.