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I read somewhere that the new MacBook Air computers (the ones with USB-C) can be charged slowly from any USB source using a USB-C to USB-A adapter.

I'd imagine that a plane USB port delivers 5W or 10W power. When doing light tasks on the Air, I would imagine that, even when not charging, would allow to extend the battery life significantly.

Can anyone confirm that this works? What cable do I need?

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Yes, I can confirm it works for MBA 2020 M1. From regular 10W (5V@2.1A) USB port it takes 1.4A. It's enough to very slowly charge it while watching FullHD video. Even with 5W port MacBook takes 0.9A and a battery is discharging just 0.2W while watching YouTube over WiFi with two steps from minimum brightness.

And it uses only one port to charge even if both are connected to power source :)

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I read somewhere that the new MacBook Air computers (the ones with USB-C) can be charged slowly from any USB source using a USB-C to USB-A adapter.

Yes. This is correct. The Type C ports on your Mac conform to the USB-PD (Power Delivery Spec) meaning it will negotiate for the maximum charge.

The default charge that comes from a USB-PD device starts out at 5V - this, coincidentally is the same voltage that legacy USB chargers output. If it can negotiate up (to a max of 20V) it will do so. Otherwise, it will simply draw the maximum which is no more than 12W (5V at 2.4A)

So, if you use a 5W charger (airplane, car, etc.), it will take forever to charge that MacBook (you'll drain battery if you attempt to use it while charging), but it will charge. It will go faster if it's a 12W or 15W port, but still be quite slow. As for the power draw, it will draw what it can - if the airplane only supplies 5W; that's all you'll get.

Your best bet is to get a proper USB-C travel charger and hopefully the airplane will have the 12V sockets (car cigarette lighter port) rather than USB ports.

As for the cables you need, if it's a USB-A port, just the USB-C to A adapter you already referenced and a USB-C cable which you should already have.

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  • I will add that there are USB-C (male) to USB-A (male) cables that will be labeled as "Quick Charge", "Dash Charge", or some other non-USB means for faster charging, these will not help you. Apple MacBook laptops only support USB-PD for charging, and using anything other than a USB spec cable will not charge the laptop faster. It may in fact slow it down. Those cables only offer faster charging if the charger and phone/laptop/whatever support the same charging protocol. Any certified USB-C to USB-A cable will support USB-PD, just look for the USB trident icon to verify it meets the spec.
    – MacGuffin
    Jan 8, 2021 at 5:24
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Someone did a nice youtube video on exactly that- charging your macbook via usbc from the regular old style usb sockets. Works fine, and doesn't "drain your mac" as some people incorrectly guessed.

MacPro USB-C can be charged with old style USB-A power sources

I'm bucking the "gotta have 61 or 90 watts of power!" trend. That high capacity allows for charging the battery very quickly, even while using your Mac to the fullest. This is the worst possible case. The more common case is a forgotten charger, or being in an airplane seat with only a USB-A available.

Going further, I much prefer a sloooow trickle charge for my macpro. I sit at a desk all day. I don't want to quick sear charge to 100%, then slow cook the battery all day. Neither is great for the battery. The quick charge is stressful, as well as leaving it plugged in after charge.

I don't want to constantly plug and unplug my mac during the day to stay in the sweet lithium charge state. I really wish Apple would implement a charge level cutoff, like a Tesla car has. Set desired charge level to, say 70 or 80%, and the mac automatically stops charging when it hits that level. Drops to 40%? Start charging again.

So since Apple doesn't have that, I'll slowly trickle charge it. Ideally, just feeding it enough power to not use the battery. Charging my macpro off of a 5w or 12w charger iPhone/iPad charger should work nicely for this.

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    While this is mostly true and indeed some practices should be adopted by more people, I don't see how all of this prose answers the question.
    – X_841
    Mar 8, 2021 at 18:40
  • The first sentence answers it- yes, you can charge a USB-C Mac from old style USB-A. The rest explains why most people might want to consider doing just that.
    – nogasbiker
    Mar 10, 2021 at 0:32
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This is similar to trying to charge your MacBook with an old school phone charger. As you indicate yourself you'd need a USB-A to USB-C cable. Enough results if you Google it.

In my experience with a MacBook 12" you get some juice from the charger, but you use more than it delivers. So you can charge your MacBook, very slowly, when it's turned off. And the battery would drain just a little bit slower when using it while connected.

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  • Can anyone confirm that this works on macbook air 2020? Oct 5, 2020 at 11:41

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