Does Charging Your Phone Overnight Damage the Battery?

​​When it comes to devices with lithium batteries, especially smartphones, there has been a lot of debate on whether or not charging for extended periods of time is damaging to the battery. There are many schools of thought surrounding this topic, along with a wide range of advice and myths about what is or isn't harmful to your phone battery. So, what is the real truth about lithium batteries? Well, it's complicated.


Can I Overcharge My Battery?

The most common myth about overnight charging is that it can overload your battery. This is simply not true. All smartphones are designed with protective measures that prevent the battery from overcharging once it's full. As soon as the battery reaches 100%, it stops charging. At this point your device runs on AC power rather than battery power. Of course, eventually, whether or not you're using it, your phone will drop to 99%. At this point, your phone will "trickle-charge", as the charger repeatedly brings it back up to 100% again. This process doesn't degrade your battery any faster than regular use.

The Real Danger: Heat

Charging overnight is not a danger to your battery in and of itself. However, temperature is a real concern. One of the most damaging things your battery can experience is extreme heat or extreme cold. Apple has publicly stated that temperatures above 35 degrees Celsius can cause permanent damage to battery life. And this means internal temperatures, not just the weather outside. If your device isn't ventilating properly then it can overheat rather easily.

This is where the danger can come in with overnight charging. Trickle-charging uses energy and generates some heat, so your phone might get too hot if it's on the charger all night and it isn't able to release enough heat. This happens when your phone is wrapped in a blanket or stuffed underneath your pillow. If you do charge overnight, the best thing you can do is make sure the device is placed in open air or on a heat sinking material. Alternatively, try a smart power outlet that shuts off after a certain time.

Above all, never plug your phone in when it's excessively hot or cold. And just in case you've heard this myth, don't freeze your phone -- please.

The Cold Hard Truth

Now we've established what can and can't cause irreversible damage to your phone battery. However, if we're talking about battery degradation over time, we have to discuss how battery life works.

The unfortunate truth is that lithium batteries are unstable. This means the battery life, or capacity, is constantly degrading no matter what. Typically, a smartphone battery will work effectively for 2-3 years. If you use best practices and avoid damage to the battery you can preserve its life a little longer, and with poor use you might see significant degradation in only one year.

Rather than avoiding over-charging, you should avoid over-discharging. Allowing your phone to reach 0% and shut off automatically can cause the battery life to degrade faster. Instead, try getting to the charger before the battery drops below 20%. Some companies report that allowing your battery to regularly discharge and charge rather than staying full all the time also can preserve its overall life.

Another piece of advice is to use name brand or certified phone cables and power adaptors. This ensures that the inner hardware of the charging cable is compatible with your phone and is providing a safe and efficient charge. Avoid cheap off-brand cables and instead opt for phone cables that are certified or designed for your phone.