iPhone 15 Pro Max back warms after turning on

Yes, absolutely normal. When first turned on almost every electrical component starts producing heat. The fact the back gets warm is a design of the engineers that developed your iPhone. If the heat didn’t dissipate through the frame, the internal components might overheat and become damaged.

Ab_781 wrote:

Another thing I was wondering, is it normal for my phone to get really warm when using apples 20W adapter

Hello~ As long as you’re not getting a message that your iPhone is too warm like below…you’re fine…

If your iPhone or iPad gets too hot or too cold - Apple Support

Also take a looked at this user tip by *Lawrence Finch* as it’s an excellent source of information…

When to charge your iPhone or iPad - Apple Community

~Katana-San~

iPhone 15 Pro Max has a faster processor, brighter screen and larger battery in same size frame, but produce substantially more heat.

Yes, a by product of charging is heat. Charging a battery is not 100% efficient, meaning trying to cram electrons into a battery creates heat. Again, the design dissipates heat through the external shell. Typically, charging is only around 60 to 70% efficient and the remainder is heat.

LD150 wrote:

Ab_781 wrote:

I had a 11 pro max previously but that did not get hot quickly as my 15 pro max does, is there a reason for this?

Twice as powerful, but I wonder why you turn it off, I never turn my main phone off.

I would wonder the same. NONE of my Apple Devices, iPhone/iPad/Apple Watch/MacBook Pro are ever turned off. When not in use at night, while I'm sleeping, they are all plugged in to charge and sync as Apple designed them to do.

Ab_781 wrote:

I had a 11 pro max previously but that did not get hot quickly as my 15 pro max does, is there a reason for this?

Twice as powerful, but I wonder why you turn it off, I never turn my main phone off.