Does your iphone 13 heat up during charging?

All phones heat up when charging, and also when discharging. It’s called the Second Law of Thermodynamics. Anything that creates or uses energy does so with some loss. That lost energy is expressed as heat. So when you charge the phone it generates heat in the power source, heat in the charger circuit in the phone, and heat as the energy goes into the battery. The faster the charging, the more heat is generated. The iPhone 13 has the fastest charging capability of any iPhone, so it will get warmer than any other model if you take advantage of the fast charging capability. Likewise when you discharge the battery; not all of the energy from the battery gets to the circuits that use it. Some of it becomes heat. If you use the cellular network for voice or data, converting energy to radio frequency signals is very wasteful; only about 30% of the energy that goes into the network components comes out as radio signals.

As a lighter view of the laws of thermodynamics, the Battelle Memorial Institute many years ago published a lay-persons explanation of the 3 laws of thermodynamics:

1. You can’t win (Energy cannot be created; that’s why there is no perpetual motion)
2. You can’t break even (There is some energy loss in every process)
3. You can’t quit the game (It is not possible to reach a state of no energy - absolute zero)

If you are charging with the cord and not wireless charging, there are 4 microcircuits in the plug that goes into the phone that will use power. In addition, the wire diameter in the cord is very small, it’s internal resistance is significant, so it acts like the heating wire on a toaster (on a smaller scale, of course). At low currents you won’t notice that it gets warm, but fast charging it will. Which brings up the point that it is very important to use a high quality cable; never a “gas station” cable. Either an Apple cable or one from a “respectable” manufacturer like Griffin, Anker, etc. And I personally don’t trust Amazon cables either, because a lot of 3rd party products on Amazon are schlock.

Your iPhone 12 charged at a lower current than the 13, so it won’t get quite as hot. If it concerns you don’t fast charge the phone; if you use a 5 watt or 12 watt charger it won’t get as warm. It will charge slower, but if you follow best practice and charge the phone overnight it won’t matter how long it takes.

For MagSafe it will get warm because wireless charging is less efficient than charging with a cord, so there is more energy loss, and energy loss is heat. The MagSafe is a 15 watt charger, and it is using 20 watts from the USB-C adapter, so that’s 5 watts of power loss even before it gets to the phone.

I bought an iPhone 13 in November and noticed that it heats up during charging. I have to agree with Lawrence Finch, the heat created during charging has to do with energy loss.. it’s not really a big deal and certainly not harmful.

There’s no plastic inside the phone, so most likely it is the case.

thebigdog14 wrote:

I’ve been using a 20 W Anker Plug and this cord: USB C to Lightning Cable 20W, [... https://www.amazon.com/dp/B07WRPW8LM?ref=ppx_pop_mob_ap_share It is also 20 W. Should I use lower Watt plugs & cords then? I usually charge over night unless I’m on the road and need a boost, so I don’t mind a slower charge. I just need a cord that is durable.

I’ve noticed that my regular USB cord will heat up too when using a mobile charger, as will the phone.

However, when I use an old USB apple plug in charger and a USB cord, the phone cools down.

Yes, that’s natural, because the old USB plug was only 5 watts (an iPad plug is 12 watts), so the charge rate is lower, and the energy loss and thus heat loss is proportionally lower. The iPhone 13 is designed to be fast charged safely, so the added heat is accounted for in the design.

If it’s not too hot to hold don’t worry about it. iPhones have built-in overheating protection; if it gets hotter than it’s design specification it shuts down and displays a message saying it has to cool off. Did you put a plastic screen protector on it, perhaps? You can always take it to a Genius Bar if you are concerned about it.

Great explanation, thank you for posting this!