system
Given the following post, respond as if you're commenting on Reddit:
human
Mysterious battery re-charge when devices turn off.

I've noticed with the past few cell phones I've had that if I have a battery level of say, 6% and I turn the phone off, when I turn the phone on again in a few hours I'll have a battery level of 11% or something like that.

What is the electrical/chemical explanation for this? Do batteries regenerate energy just by being dormant for a short period of time?
gpt
Your phone measures the percent of power left in the battery by the voltage it produces. By letting the battery sit it might cool, thus outputting a larger voltage which the phone takes to be a higher charge level. In any case no additional energy is gained.