iPhone 17 Pro Max only charging at 25W with 40/60W charger + Thunderbolt 4 cable

[RyanFlynn]

Hey friends,


I’m testing charging speeds on my new iPhone 17 Pro Max. With a 40W/60W charger and a Thunderbolt 4 cable, I’m only seeing ~25W. That works out to about 28% in 20 minutes instead of the advertised ~50%.

I’ll try again with the included cable once I drain back to 0% battery, but curious if anyone else is running into this.

So far, I see two possible issues:

1. The Thunderbolt cable doesn’t actually support the full charging speed.
2. I stressed the phone with benchmarks, so the battery/phone is too hot and throttling charging.

I’ll keep testing and report back, but would love to hear if anyone else is seeing similar numbers.

—Ryan

 

[RyanFlynn]

Ok, So I've tried 3 different cables, with a totally good phone from 0%. I'm only getting to 31% in 20 minutes.

Cables tried:

2 meter thunderbolt 4 cable.
1 meter thunderbolt 3 cable.
iPhone 17 pro max stock cable that was included in the box.

confirming that this is the charger I'm using:

40W Dynamic Power Adapter with 60W Max

The 40W | 60W Dynamic Power Adapter provides powerful boosts for faster charging speeds. Buy now at apple.com.

www.apple.com

 

[GrindedDown]

Well that’s no good. I wonder if there is a pending firmware update for the phone?!

 

[RyanFlynn]

I hope so!