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Why Charging Your Gadgets Over 80% Is Such a Bad Idea | iFixit News
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A lot of charging circuits and battery designs already do this transparently.
Yes. Batteries are bags of chemicals. They don't really have percentages. Where you decide 100% is is somewhat arbitrary and up to the battery management.
What the system shows the user may be even a completely different number and there may be software adjustable values.
It's inherently a made up number and a manufacturer can decide to be more brutal or more sparing in how they treat the chemicals.