USB Power Output of M1 and M2 MacBook USB-C/Thunderbolt Ports?

[Citizen45]

Does anyone know what the USB power output of the USB-C/Thunderbolt ports is for the M1 and M2 MacBooks?

Interested in knowing if my devices would charge at full speed when plugged into the MacBook.

How many watts/volts/amps can it output?

 

[altaic]

Are you asking if the USB-C ports support USB PD? If so, I’m kind of interested myself. I may give one of my USB testers a whirl and report back.

Edit: My USB variable load isn’t rated for PD, so that’s a no go. The only other thing I have on hand is a 30W USB-C soldering iron, but I’m not about to see if it’s actually in spec by plugging it into my MBP 😬

 

[wilberforce]

Minimum power output for the first port is 15W, and 7.5W for subsequent ports, per thunderbolt/USB4 specification.

I don't know the actual power output, but I suspect it is not more, because it would require stepping up the voltage from the base 5V to 9V or higher. (Max allowed power at 5V is 15W.)

USB4™ Thunderbolt3™ Compatibility Requirements Specification | USB-IF

usb.org

 

[Mike Boreham]

In my experience if you plug in an accessory which is asking for too much current you will get a pop up message warning about it.

My understanding is that USB-PD is a protocol for delivering up to 100W to the machine from a wall changer or power brick. It is not applicable to charging accessories from the machine.

 

[wilberforce]

In my experience if you plug in an accessory which is asking for too much current you will get a pop up message warning about it.

My understanding is that USB-PD is a protocol for delivering up to 100W to the machine from a wall changer or power brick. It is not applicable to charging accessories from the machine.

The protocol applies to both, if the ports comply with the USB4/TB3/TB4 specifications, which require compliance.
The USB-PD protocol does not specify how much power must be delivered, just specifies how the different power levels are to be implemented.

 

[Mike Boreham]

The protocol applies to both, if the ports comply with the USB4/TB3/TB4 specifications, which require compliance.
The USB-PD protocol does not specify how much power must be delivered, just specifies how the different power levels are to be implemented.

Thanks very much for clarifying. In practice what does USB-PD do when charging an accessory? I assume it negotiates one of the USB-PD voltages? Are any chargeable small accessories USB-PD compliant, apart from iPhones and iPads? In any case I assume it is limited to 15W.

 

[wilberforce]

Thanks very much for clarifying. In practice what does USB-PD do when charging an accessory? I assume it negotiates one of the USB-PD voltages? Are any chargeable small accessories USB-PD compliant, apart from iPhones and iPads? In any case I assume it is limited to 15W.

Yes, it will negotiate a power profile (combination of voltage and wattage). I believe if the accessory is not USB-PD compliant it will default to 5W or something like that (don't have time to look it up).

 

[Citizen45]

So... there's no clear answer then?

We don't know if the M1/M2 Mac's can charge the iPhone at full "fast charge" speed?

 

[altaic]

So... there's no clear answer then?

We don't know if the M1/M2 Mac's can charge the iPhone at full "fast charge" speed?

Hah, why didn’t I think about trying my phone? Anyway, testing that now with my iPhone 12 Pro (and USB tester J7-c):

• Using any port (tried them all) on my 16” MBP M1 Max— charging with 2.48A @ 5.06V, so 12.55W
• Using my MBP power brick, it charges with 1.55A @ 8.80V, so 13.64W

Technically, it isn’t fast charging from the USB-C ports on my MBP, but difference is only 8.7% better with USB PD fast charging from the power brick 🤷‍♂️

 

[jwahaus]

So... there's no clear answer then?

We don't know if the M1/M2 Mac's can charge the iPhone at full "fast charge" speed?

On my M1 Mini it's my understanding that the USB Type A ports can deliver 500mA and the USB Type C ports can deliver 900mA of current. The ports don't support USB PD. I believe the MBP is the same (minus the Type A ports).
The system report lists these values as the "Current Available" line.