Charging Your iPhone Overnight: Does it Damage the Battery?

Time is of the essence when it comes to our phone batteries, and there is a lot of hearsay about how to preserve your phone’s power supply and sure-fire ways to burn through the battery fast. You’ve probably heard warnings against leaving your iPhone plugged in all night, and after the unforgettable recall of the Samsung Note 7 after units began bursting into flames, no one wants to worry about waking up to a phone-fire.

However, is there evidence behind these claims? Is it really dangerous to leave an iPhone plugged in overnight, and does it actually damage the battery? Let’s take a look at the battery science.

Charging Your iPhone Overnight Does it Damage the Battery?

The Overcharging Myth

The most common claim about overnight charging is that you can over-charge your phone’s battery. This is just not true. All iPhones are designed with protective features that stop charging once the battery is full. When your phone reaches 100%, charging stops; the phone will simply run on AC power rather than battery power if it remains plugged in.

Of course, the battery will soon drop to 99%. When this happens, the phone will “trickle-charge” as the battery goes between 99% and 100%. Trickle-charging doesn’t degrade your phone’s battery any faster than regular use.

Be Wary of Heat

The only real danger to your phone’s battery is excessive heat. An iPhone is almost definitely not going to get hot enough to sustain battery damage while it’s charging overnight. If this does happen to a phone it’s likely due to a manufacturing issue — hence the rapid recall of the Note 7.

That being said, charging does generate some amount of heat, and internal phone temperatures can rise if the device doesn’t have any kind of ventilation. For example, stuffing your phone underneath pillows and blankets can cause it to heat up too much. Excessive heat or cold can cause irreversible battery damage.

So, the best advice for overnight charging is to make sure your phone is in open air or sits on a heat sinking material. If you love snuggling up next to your phone at night, as many of us do, try a smart power outlet that turns off after a certain time to avoid overheating your phone.

How to Preserve Your Battery

With the myth of overnight charging out of the way, how can you preserve the battery life of your iPhone? Well, the unfortunate truth is that lithium batteries are always degrading, so no matter what you do, your battery will wear out over time. There are a few ways to help it last a while.

Instead of avoiding over-charging, you should actually avoid over-discharging. In other words, don’t let your phone battery drop all the way to 0% and shut off. Ideally, start charging your battery before it reaches 20%. This can help preserve battery life in the long term.

The other best thing to do is always use certified charging cables and power adaptors, preferably name brand. If you have an iPhone, you should be using Apple or Apple-certified chargers for your devices. Cheap off-brand cables may not provide a safe and efficient charge.