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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.
Laptop folks reading this - check your bios settings. My recent Dell (and I'm sure other brands are similar) has options for this. It has a "usually plugged in" setting, but I manually chose to limit charging to 80%, which is an option in the same place.
Obv if this is bad for your use case, don't do it.