Will a > 30W charger charge a rMBA any faster?


Macdctr

macrumors 6502a
Nov 25, 2009
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The answer is if your MBA comes with a 30W power adapter and you get a 45w power adapter the laptop will only go at the 30w rate. iirc, the apple power adapter changes it's output depending on the computer it is attached to.

For example I can attach my 2012 MBPr power adapter which is an 85W power adapter to my 2015MBA which comes with a 45w power adapter. My 2015MBA does not charge any faster using the higher capacity power adapter because it supplies power at 45W to my 2015MBA.
 

kohlson

macrumors 68020
Apr 23, 2010
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I think it probably will, based on my own anecdotal evidence. My daughters used to steal my 15-MBP chargers for use with their 13-MBAs. "It charges faster," they would say. And when I use an iPad charger to charge my phone, it charges faster.
But I agree with @Macdctr in that charging rates depend on two things: source delivery capabilities, and device reception capabilities.
 

BLUEDOG314

macrumors 6502
Dec 12, 2015
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Been meaning to test this with my KillAWatt. In my experience so far this is much more beneficial with iOS devices than Macs. For example, in very brief testing with my 2017 MBP 15" Ive never actually seen it draw more than 56 watts even on its 87 watt adapter. This seems to be an actual thing with the 15" MBPs 2016 and newer. I haven't tested my 87 watt adapter on my 2016 rMB yet but I can't see it pulling more than 30 watts. I also own an Anker Atom PD1, and find it to charge my iPhone X at most around 13-15 watts, and my 2018 iPad 11" at the full 30 watts.
 

biohead

macrumors 6502
Jun 18, 2010
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West Drayton, UK
The answer is if your MBA comes with a 30W power adapter and you get a 45w power adapter the laptop will only go at the 30w rate. iirc, the apple power adapter changes it's output depending on the computer it is attached to.
I'd be interested to know how 3rd party adaptors react and whether they will allow any more power to the laptop. I'll try and grab one over the weekend to test.
 

jesChexin

macrumors member
Mar 8, 2018
37
24
Just got a retina MBA and looking for a travel charger. I'm interested in these smaller gallium ones:

https://www.anker.com/deals/powerport_atom ($30, 30W, really small, but not out yet)

https://www.ravpower.com/p/ravpower-45w-type-c-pd-wall-charger.html ($50+, 45W, bigger, available now)

Will the 45W charger charge the MBA any faster than the 30W?

If not, it will help justify my wait for the Anker
Hi OP. I asked this question to the forum back in January. Consensus is that, while certain iOS devices designed to be capable of fast charging can obviously fast charge, Apple’s MacOS laptops cannot. Apparently, whichever charger came in the box with your MacBook/MacBook Air/MacBook Pro is designed to charge at the max limit for which that particular device can charge (so, for the new 2018 rMBA, a max of 30 watts).

https://forums.macrumors.com/threads/2018-mba-fast-er-charging-available.2166677/
 

Macdctr

macrumors 6502a
Nov 25, 2009
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Ocean State
I'd be interested to know how 3rd party adaptors react and whether they will allow any more power to the laptop. I'll try and grab one over the weekend to test.
With the unibody MacBook Pro/Air design I have stayed with authentic Apple power adapters. My niece tends to destroy her power adapter for her MBA thanks to her cat and then I hear about it... I will always tell her even though the Apple power adapter costs more to get it so there won't be any issues.

I'm sure you can use any 3rd party power adapter but I myself will stay with authentic Apple power adapters for my computers and will always recommend getting them.
 

BLUEDOG314

macrumors 6502
Dec 12, 2015
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I'm sure you can use any 3rd party power adapter but I myself will stay with authentic Apple power adapters for my computers and will always recommend getting them.
I completely agree with pre 2016 devices that use magsafe, but devices that use power delivery are entirely safe to charge on a "good" power delivery charger. Now that's not to say we will never see cheap knock off PD branded chargers that are essentially "fake", but for now I think we are safe. Stick to a good brand and you should be fine.
 
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biohead

macrumors 6502
Jun 18, 2010
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West Drayton, UK
Yeah, I was talking about using a proper USB-PD supply from a well known company (and a genuine one at that). USB-PD is a standard - just avoid the cheap ones from an unknown brand or potential knock-offs.
I was wondering if Apple somehow had tweaked their implementation of PD so they basically prevented the Air from charging quicker (wouldn't be a surprise!).

I have managed to grab hold of a Lenovo 45W USB-PD brick and been using it for a while:

Screenshot 2019-02-15 at 17.35.59.png


It's correctly detected as a 45W charger but that's the limit of information given. Nothing like the Apple one which gives a fair bit more. I don't know whether those extra bits from the Apple charger are an option for USB-PD, or if Apple are adding their own proprietary bits onto the USB-PD standard. Still, a 3rd party charger is detected correctly and charges the MacBook Air without issue. It outputs at 20V for those interested.
Also, a big point that I've noticed is that it (the Lenovo charger) is properly grounded - so the case doesn't "vibrate" when you run your hand over it when it's plugged in. That alone puts me off using the Apple adaptors as I don't have the extension cable to hand (in the UK, that's the only way to ground it).

Under charging, with nothing else done on the Air, this is what iStat is showing:
Screenshot 2019-02-15 at 17.36.17.png

And it generally stays in that region.
30W, just like the Apple one.

HOWEVER.... When I run something intensive:
Screenshot 2019-02-15 at 17.51.08.png

It starts to draw up to 45W. This is only what's available on iStat so I'm still taking it with a pinch of salt but I think it's enough to say this needs to be looked at in a bit more detail. I don't have a USB-C power meter to read the voltage/current directly through the port yet so I can't really do much more anytime soon.
 
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biohead

macrumors 6502
Jun 18, 2010
428
5
West Drayton, UK
Just as another follow up to this, when the MBA has a completely flat battery, it is drawing the full 45W from the Lenovo charger even on idle. My last test was at about 80% so likely not taking the charge at full rate. I don't have access to any higher rate ones but I'd like to know what the max the MBA will take now.

So it certainly looks like with a 3rd party charger you can charge the MBA faster than when using an Apple one.
 

BLUEDOG314

macrumors 6502
Dec 12, 2015
349
86
So it certainly looks like with a 3rd party charger you can charge the MBA faster than when using an Apple one.
It would be nice if faster charging was supported all around. At 40% my 2016 rMB does not charge over 30 watts. Being able to charge my 11” iPad at 30 watts is great however.