MacBook Air M1 charging with Apple 20w USB-C power adapter showing only 15w

[sdluzzi]

Hi there! I bought an Apple 20w USB-C power adapter for my new apple watch and to check if it was genuine I connected it to a MacBook Air M1 2020 and under system settings it shows as an Apple charger but what concerns me is that it only shows 15w instead of the 20w output that the charger has, is that normal?
I know the MacBook comes with a 30w power adapter but it concerns me that the one I bought (20w) only shows 15w input when connected to the MacBook. Anyone knows why or if this is normal somehow?
Thanks a lot in advance!

 

[Bigwaff]

Are you using the supplied USB-C cable that came w/ your MBA M1 2020?

 

[sdluzzi]

Are you using the supplied USB-C cable that came w/ your MBA M1 2020?

Yes, I’m using the usb-c cable that came with the MBA M1 (actually is the only usb-c to usb-c cable that I have). Have you tried the 20w Apple adapter on your Mac and showed you 20w under system settings? I’m trying to figure out if that wattage could change depending on the usage of the Mac while charging with the 20w adapter or if there is something wrong with the charger.
If I use the supplied 30w charger and cable it shows the 30w under system settings.
Thanks!

 

[JPack]

Adapter is unlikely to be genuine. The AC Charger Information (serial, name, manufacturer, etc.) can all be programmed for fake adapters.

20W adapter will show 20W. That is the max. capability as determined by USB-PD negotiation, not a snapshot of current draw.

 

[Superhai]

Unless your USB cable or ports are faulty or not able to use PD the charger is most likely fake. It is not able to negotiate a USB-PD connection and then it would default to the max 5V 3A. But then I doubt it would show serial numbers and so on.

 

[sdluzzi]

Unless your USB cable or ports are faulty or not able to use PD the charger is most likely fake. It is not able to negotiate a USB-PD connection and then it would default to the max 5V 3A. But then I doubt it would show serial numbers and so on.

What I don’t understand is if the Mac can pull just the power it needs from the charger, even using the provided 30w according to the use of the Mac at that moment or if it always pulls the maximum watts from the charger… I mean, if it’s plugged with the 30w charger but you’re just browsing the web maybe it pulls just less watts from the charger, and when you do some heavy stuff it pulls the full “wattage” from the charger…in this case 30w or 20w depending the charger I’m using.
By the way, I bought the 20w Apple charger from an Apple authorized reseller (premium reseller in this case) here in my country (we don’t have Apple stores yet) so I suppose it should be genuine…

 

[JPack]

What I don’t understand is if the Mac can pull just the power it needs from the charger, even using the provided 30w according to the use of the Mac at that moment or if it always pulls the maximum watts from the charger… I mean, if it’s plugged with the 30w charger but you’re just browsing the web maybe it pulls just less watts from the charger, and when you do some heavy stuff it pulls the full “wattage” from the charger…in this case 30w or 20w depending the charger I’m using.
By the way, I bought the 20w Apple charger from an Apple authorized reseller (premium reseller in this case) here in my country (we don’t have Apple stores yet) so I suppose it should be genuine…

Using your logic, it would still show 15W when you switch between your two adapters.

It is a fact macOS shows maximum output of the adapter and not a transient number. It’s also a fact that many fake adapters have serial and name data programmed in. I’ve seen several.

 

[DaniTheFox]

Hi there! I bought an Apple 20w USB-C power adapter for my new apple watch and to check if it was genuine I connected it to a MacBook Air M1 2020 and under system settings it shows as an Apple charger but what concerns me is that it only shows 15w instead of the 20w output that the charger has, is that normal?
I know the MacBook comes with a 30w power adapter but it concerns me that the one I bought (20w) only shows 15w input when connected to the MacBook. Anyone knows why or if this is normal somehow?
Thanks a lot in advance!

View attachment 2321387

I understand that USB-PD is not mandatory for USB-C. Only 7.5W (5V by 1.5A). There is an optional 15W (5V by 3A), still without USB-PD (many USB-C/TB hubs/docks have this). So it looks like this adapter only implements the optional USB-C standard. Or USB-PD is not working for some reason.

 

[sdluzzi]

It would be really great if someone with a genuine 20w Apple usb-c power adapter could try it on a MacBook and see under system settings as showed on the OP screenshot what “wattage” shows there for him/her or even better post a screenshot/photo to finally resolve this issue. Thanks in advance!

 

[chrfr]

It would be really great if someone with a genuine 20w Apple usb-c power adapter could try it on a MacBook and see under system settings as showed on the OP screenshot what “wattage” shows there for him/her or even better post a screenshot/photo to finally resolve this issue. Thanks in advance!

I can't easily get a screen capture, but it shows 20W.
In System Information below the "Connected" line, I also have an ID which is missing on yours. On mine it shows ID: 0x7004.
The serial number shown matches what is printed on the charger as well, but that is also easily faked. I do not believe you have a legitimate charger.

 

[rocketbuc]

How about you download Coconut Battery to see what wattage it draws? Once you start to stress the MacBook it should show the maximum possible wattage drawing from the charger.

 

[sdluzzi]

I can't easily get a screen capture, but it shows 20W.
In System Information below the "Connected" line, I also have an ID which is missing on yours. On mine it shows ID: 0x7004.
The serial number shown matches what is printed on the charger as well, but that is also easily faked. I do not believe you have a legitimate charger.

Thank you so much for taking the time trying it on your Mac, can I ask you which MacBook model you tried it on? And also (I know I’m asking too much now) can you please send me a screenshot of what you see under system settings for the ac adapter?cause I paid full price for this charger on an authorized reseller so I can claim with your screenshot that they sold me a fake charger?
Thanks in advance!

 

[PaulD-UK]

If it's a USB-C PD charger it won't charge an Apple Magic Keyboard or mouse - because they're not 'PD smart'.
If it does charge them it's an ordinary 5v 3A charger.
Maybe that's what an Apple Watch needs, which is why they sold it to you?

 

[chrfr]

Thank you so much for taking the time trying it on your Mac, can I ask you which MacBook model you tried it on? And also (I know I’m asking too much now) can you please send me a screenshot of what you see under system settings for the ac adapter?cause I paid full price for this charger on an authorized reseller so I can claim with your screenshot that they sold me a fake charger?
Thanks in advance!

It was an M1 Air. I cannot easily get a screen capture on here from that computer.

 

[PaulD-UK]

Taken with the 20w PSU from a 2021 M1 iPad Pro, connected to a 2016 15" MBP.
My other 20w USB-C charger from a HomePod Mini is the same with different Serial No:
They don't charge this MBP.

 

[Superhai]

What I don’t understand is if the Mac can pull just the power it needs from the charger, even using the provided 30w according to the use of the Mac at that moment or if it always pulls the maximum watts from the charger… I mean, if it’s plugged with the 30w charger but you’re just browsing the web maybe it pulls just less watts from the charger, and when you do some heavy stuff it pulls the full “wattage” from the charger…in this case 30w or 20w depending the charger I’m using.
By the way, I bought the 20w Apple charger from an Apple authorized reseller (premium reseller in this case) here in my country (we don’t have Apple stores yet) so I suppose it should be genuine…

Even legitimate businesses have been scammed, or could take shortcuts.
Anyway the thing about USB-PD is that to go above 15W you have to change the voltage from the standard 5V. So the Mac can't just draw more power just like that. There have to be some sort of communication. If the Mac tried to draw 30W from a 5V adapter, it means 6A current drawn from it. That would likely quite quickly fry some components in the long run.
To get 20W, the voltage changes to 9V and with a max current of 2.2A.

 

[magbarn]

I think your adapter is counterfeit, as there's never been a 15 watt genuine Apple USB C charger. When I get home I'll try to connect my ipad's genuine Apple 20 watt adapter using the thicker apple 100 watt cable to my MBA M1 and post a screenshot

 

[magbarn]

Definitely counterfeit.
This is my iPad Pro's 20 watt Apple charger plugged into my M1 MacBook Air with Apple USBC 100 watt cable.