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Should I leave my phone plugged in overnight?

Charging all of your devices overnight is convenient, but just how safe is it?
By
March 22, 2022
Samsung Galaxy S22 Plus fast charging
Eric Zeman / Android Authority

From performance to features, modern smartphones exceed our expectations in nearly every aspect. Battery life, however, cannot be taken for granted and requires some attention on your part. Similarly, you may have heard claims that charging your phone for long periods could lead to overcharging and may even wear out the battery sooner than expected. But are these concerns really valid and just how much damage are you doing to your smartphone by leaving it plugged in overnight?

Related: Android phones with the best battery life

What happens when you charge your smartphone overnight

Xiaomi 12 Pro Turbo Charging
Eric Zeman / Android Authority

Let’s start with the basics. When you use your smartphone and discharge its lithium-ion battery, positively charged ions move from the anode to the cathode. Depleting the battery essentially means that you’ve transferred (or spent) all ions. Charging a battery essentially forces a similar transfer of ions, but in the reverse direction. However, your smartphone’s battery doesn’t pull current directly from a wall adapter to accomplish this.

Most modern electronics — and certainly all smartphones — contain power management integrated circuits (PMICs) that sit between the charging port and battery. These miniature electronic devices essentially control the rate and flow of current to the battery. You see, the amount of power your phone draws reduces over time in order to reduce strain (and thus, wear) on the battery. Moreover, once the battery reaches 100% charge, the phone’s circuitry will intelligently stop drawing power from the wall adapter altogether.

That’s right — if you keep your phone plugged in at 100% charge, it simply won’t charge anymore. Instead, it will sip power from the battery until it drops to 99% (or thereabouts). The above cycle then simply repeats itself until you unplug the device. Put simply, you can safely charge your devices overnight without having to worry about damaging their internals.

Modern electronics automatically stop pulling current once their batteries reach 100% charge. However, charging to full each time isn't ideal for battery longevity.

While you’ll likely never overcharge your smartphone’s battery, leaving it plugged in overnight does have a few drawbacks you should be aware of. The electronics industry’s consensus is that lithium-ion batteries survive the longest when kept between 20 and 80% charge. Of course, this is a rather narrow range — you’ll only get around half of your device’s already-limited battery life if you strictly stick to this guideline. However, you can simply try to prevent it from reaching either extreme as much as possible. In other words, top-up your smartphone before it can reach 0% and don’t charge all the way during the day.

Related: Charging habits to maximize battery life

Having said that, manufacturers already sneakily discourage you from charging your device’s battery to true 100%. Our testing has revealed that many smartphones report a 100% reading much before they stop pulling power from the wall. Some manufacturers like Asus also offer a maximum charge limit (like 80%) to prolong the battery’s life.

How to charge your device without damaging its battery

Google Pixel Stand wireless charging Galaxy S21 Ultra
Robert Triggs / Android Authority

A major factor that is known to shorten the lifespan of lithium-ion batteries is heat. To that end, ensure that your smartphone is placed in a cool and ventilated area while it’s charging. Keeping it sandwiched between two pillows, for example, could lead to overheating, a slower charge rate, and lower the battery’s lifetime. Wireless charging, while convenient, produces plenty of heat too, so use it sparingly if you want maximum battery longevity.

Heat accelerates battery wear. To that end, consider turning off fast charging overnight or simply using a slower adapter.

Fast charging your smartphone generally increases heat output as well. To that end, it might be worth downgrading your bedside adapter to a slower one that charges at 5 or 10 watts. That’s still plenty for you to wake up to a fully-charged smartphone in the morning. If you own a recent Pixel smartphone, your phone will automatically charge slower than the maximum speed at night thanks to the exclusive Adaptive Charging feature. However, this will only work if you have an alarm set between 3 AM and 10 AM.

See alsoHow to pick the right charger for your smartphone

All in all, though, your device already has many built-in safeguards to prolong its life. Samsung, for one, claims that it designs its smartphones to retain as much as 95% of its total battery capacity after two years of use. This is likely why the company is one of the most conservative in terms of faster charging tech.

Even if your smartphone’s battery health degrades, however, don’t forget that replacement options exist too. You can typically get your smartphone’s aging battery replaced for anywhere between $40 and $100 all-inclusive, depending on the manufacturer. While that’s a decent sum, it’s arguably a lot cheaper than splurging on a brand-new smartphone. And, of course, it stops you from worrying about plugging in overnight or whenever suits you best.

Up next: 6 common battery myths you probably believe