[fulafel]

The last 10-20% of the charging causes most battery wear (many times more than in the mid band). So charging from almost-full to full many times per day is going to be harder on the battery than charging fewer times per day.

This is especially pronounced on phones, where batteries are already calibrated to have a high charge cutoff (ie battery longevity vs capacity compromise is heavily at the capacity end).

[int_19h]

What I don't get is why phones can't be configured to just never charge past 80% or so, for people who rarely need that 100%, and would rather the battery wear less.

It's a thing for some laptops; e.g. Lenovo specifically advertises such a setting.

[fulafel]

Apparently you can do it on rooted Android, though I haven't tried it (eg https://www.androidexplained.com/battery-charge-limit/)