I am charging my iPhone from a newer Thunderbolt 3/USB C enabled MacBook (in my case MacBook Pro 2016) with USB C to lightning cable from Apple.
What I know is:
For example there is an iPhone 8/8 Plus/X or a newer iPad Pro 13
with computer (default(?)) or iPhone charger wall plug: 5W (5V 1A)
with iPad charger or 2.4A powerbank USB A to lightning: 12W (5V 2.4A)
with MacBook charger wall plug (29W or larger) USB C to lightning: 29W fast charging
Anything I do from a 2016 MacBook Pro 15 it seems I get the default charging speed (5W) through USB C despite the same USB C to lightning cable with the MacBook wall plug can fast charge (29W).
The USB C/Thunderbolt 3 standard though supports 100W. Is there a (highly likely unofficial) way to tell my Mac that the iPhone/iPad plugged in via the USB C to lightning cable would like to take a faster charge?
So is there a way to charge from a Mac an iPhone/iPad with 12W or 29W instead of the "default" 5W?
Best Answer
No, a USB-C to lightning cable that is Apple certified will charge iOS devices at the fullest capacity the new MacBook Pro will provide to a USB and lightning connector.
That same cable will fast charge from USB-C PD compatible chargers like the Apple ones.
iOS doesn’t present as thunderbolt so you don’t get that amount of power over lightning connector.
The technical details are available to any organization that participates in the MFI program - https://en.wikipedia.org/wiki/MFi_Program and the signaling between devices to decide to fast charge is somewhat sophisticated and possibly has an encryption / identity key (I haven't seen the specifications so that part is speculation).
There’s nothing hidden. Apple could decide to increase the charge since they control all the drivers and power management and SMC and lightning specifications. They just chose the 5w you are seeing.