Yes, it's safe to leave your smartphone plugged into the charger overnight

Hollis Johnson/Business Insider
Your smartphone is smart, and so is its battery.
For years, the myth has persisted that plugging your smartphone in a charger while you sleep will cause some sort of harm to that phone's battery. Though many people do it anyway, others warn that if you continue to charge a phone that is already fully charged, you'll waste away its battery's capacity.
But while those fears may have made sense with the batteries of years ago, they're overblown today.
Tech Insider/Antonio Villas-Boas
But leaving your phone in the charger overnight, even when it's fully charged, won't do much to change how frequently its battery runs through cycles. That's a process that begins as soon as you start using your phone, and there's little you can do to stop it.
"In terms of the gradual erosion of battery life, what must be understood is that phone batteries are constantly in a state of decay," says a spokesperson for battery and charger accessories maker Anker. "Sleeping with a phone charging overnight will make no noticeable difference in the process."
Antonio Villas-Boas/Business Insider
"Smartphones, as the name would suggest, are smart," said the Anker spokesperson. "Every unit has a built-in chip that will prevent charging once 100% capacity has been reached. Therefore, provided that the phone in question is purchased from a verified and legitimate retailer, there should be no danger in leaving the phone charging overnight."
The idea of charging overnight being harmful - or causing series of "mini-charges" that continuously drain the battery - typically comes from people's experiences with older tech, Wiens says.
"I think what gives people this feeling is that back in the day some phones or some laptops would go back and forth between 99% and 100% [on their battery indicators]," he says. "That had more to do with measuring errors of what the software was showing you more than anything else."
Antonio Villas-Boas/Business Insider
Removable batteries aren't too common in today's smartphones, but it's still possible to have an expert do the job when needed.
Wiens says the most common complaint he sees with regard to smartphone battery life is people saying their device either won't charge above a certain point, or or will die out at a percentage above zero.
Those suffering from this may just need to get a replacement battery, Wiens says, but they could also try discharging their device all the way down to 0%, then filling it back up again. This will effectively "recalibrate" the battery's internal counter; Nintendo recently suggested a similar method to fix a battery issue on its Switch console.
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