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Why Charging Your Gadgets Over 80% Is Such a Bad Idea | iFixit News
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This is a most excellent place for technology news and articles.
They already did. The percentage range on your phone's battery display is basically a usable range rather than an absolute range. The article talks about phone manufacturers making changes to their charging systems to optimize battery function, but the headline bit about not charging past a certain point has been taken into account by Android and iOS for ages.
Very few android phones actually have this feature, most manufacturers strip it