I posted something similar in the other comment section, but I know there's not a lot of overlap, so I'll post it here too.
Yes, that "Battery Recharge" condition is real. It's clinical depression.
Clinical depression happens when a person's brain doesn't produce enough dopamine and serotonin, which are the primary pleasure and reward hormones. This means that everything feels less pleasurable and rewarding than they're supposed to. Which leads to a severe lack of motivation for just about everything.
For people with clinical depression, feelings of joy and contentment are somewhat muted. You go through life with everything feeling a bit gray and dull. The severity of this feeling can fluctuate over time, and at its worst, it can even fill you with overwhelming feelings of despair and hopelessness.
To put it simply: Not only does it take more time to "recharge" your "batteries," but it also takes a lot more effort to do pretty much anything. In severe cases, even just taking showers or brushing your teeth can take too much effort.
The worst part is, when you're in one of those severe episodes, all you want is to be left alone. But isolating will only make things worse.
So what Mio really needs right now is for her friends to reach out to her and offer support. They definitely shouldn't bust the door down and try forcing her to socialize, but just being there for her will help a lot.
Also, medication can't cure depression, but it sure as hell can help, if used properly.
Source: It's me. ihavecripplingdepression.gif