Can 15w charging sustain the battery of a MacBook Air in use?

[Hoshiko]

I just bought a secondhand thunderbolt hub for very cheap but just found out that it only provides 15w power delivery.

I’m planning to buy an M2 MacBook Air and use the thunderbolt hub to power it throughout the day as I need it for online classes. Obviously, M2 is not out yet but I wanted to ask if someone here has any real-world experiences using an M1 MacBook Air with only 15w of charging and not having it drain completely when using it like a desktop computer.

From Apple’s M2 graphs in WWDC2022, I saw that the chips’ max wattage is around 15w. This would be perfect for my use case as the battery will not completely deplete when I’m using it and will charge overnight. I also searched around Google and found someone saying that the M1 MacBook Air only draws around 10w. Can someone confirm this? And can 15w charging sustain the battery or can it also slowly charge it?

Sorry if my post is kinda all over the place but my main question is really just asking if 15w is enough for desktop use.

 

[jav6454]

As long as the power draw by the Mac is less than 15W, I see no reason why it shouldn't. Remember, what the CPU uses != overall system power draw.

 

[jerryk]

That sounds close to me. The charger shipped with the M2 and M1 units is 30W. With that charger, my M1 Air recharges while I am using it for Youtube or online conferencing. But, recharging takes a while when I am actively using the unit. That is with screen brightness at 40% or so.

Can I ask why you would not just also plug in the charger that comes with the M2 Air? I assume the Air's power system would be able to correctly determine which charger provides the most power and use that one.

 

[Hoshiko]

That sounds close to me. The charger shipped with the M2 and M1 units is 30W. With that charger, my M1 Air recharges while I am using it for Youtube or online conferencing. But, recharging takes a while when I am actively using the unit. That is with screen brightness at 40% or so.

Can I ask why you would not just also plug in the charger that comes with the M2 Air? I assume the Air's power system would be able to correctly determine which charger to use.

I honestly just want the one-cable aesthetic/convenience when I use it with my desk setup. I can also leave the magsafe charger in my bag for when I need to recharge outside. Also, I found out that the M2 can ship with the new 35W dual charger, where the macbook charges with 17.5W when two devices are charging at the same time. So I thought that maybe 15W is enough cuz there’s only a 2.5W difference.

 

[jerryk]

I honestly just want the one-cable aesthetic/convenience when I use it with my desk setup. I can also leave the magsafe charger in my bag for when I need to recharge outside. Also, I found out that the M2 can ship with the new 35W dual charger, where the macbook charges with 17.5W when two devices are charging at the same time. So I thought that maybe 15W is enough cuz there’s only a 2.5W difference.

Sound reasoning.

I would just give dock a try when you get your M1. Worse is you get another cheap higher wattage USB-C charger for your desk and leave the one that came with the unit in your bag.

There are always sales on USB-C chargers on Amazon and elsewhere. I pretty much have them and cables in drawers all over the house and on all my desks so I don't have to walk somewhere to find them (pretty lazy huh?). And lately, even my monitors have them built-in.

 

[rm5]

Might work. Most power draw I've seen from my M1 MBA is around 13 W, with the CPU and GPU maxed out. But then you are straining the battery and power adapter, because then it's only charging with 2 W at full load. At least I think that's how it works.

 

[Hoshiko]

Might work. Most power draw I've seen from my M1 MBA is around 13 W, with the CPU and GPU maxed out. But then you are straining the battery and power adapter, because then it's only charging with 2 W at full load. At least I think that's how it works.

Oh is slow charging supposed to damage the battery? I thought that fast charging would but slow or trickle charging won’t. Then again, I havent really researched about this extensively.

Also, wdym by straining the power adapter? I’m planning to use the 15W PD charging from a thunderbolt dock and would using this strain the dock?

I‘d also like to ask you what apps or what kind of workflow to you use to reach your 13W average?

Sorry for all of these questions hahaha.

 

[mr_roboto]

Oh is slow charging supposed to damage the battery? I thought that fast charging would but slow or trickle charging won’t. Then again, I havent really researched about this extensively.

Also, wdym by straining the power adapter? I’m planning to use the 15W PD charging from a thunderbolt dock and would using this strain the dock?

You're right and the other poster is incorrect to raise these as concerns. Slow charging is almost always better for batteries than fast, and doesn't strain the power adapter.

 

[jdb8167]

During the work day, I mostly see about 2.5-4.0W on my M1 MacBook Air. This is for the battery discharge which is available from ioreg. Obviously it also goes much higher but it is bursty and not something that happens for very long for my work (right now React dev work.) I'm close to ending my day and I'm currently on 67% after a full 8 hours on battery.

I would have no problem maintaining and charging with 15 W over a work day. And since the battery life on a M1 MacBook Air is about 12-15 hours and I have it on a charger overnight, there wouldn't likely ever be an issue with not fully charging the battery.

 

[velocityg4]

The battery itself is probably 45w to 60w. I didn’t care to look it up so just gave a range typical to that size laptop. So, if you get over 4hours for your uses on battery. The same usage and brightness should be handled by a 15W charger.

 

[rm5]

Oh is slow charging supposed to damage the battery? I thought that fast charging would but slow or trickle charging won’t. Then again, I havent really researched about this extensively.

Also, wdym by straining the power adapter? I’m planning to use the 15W PD charging from a thunderbolt dock and would using this strain the dock?

I‘d also like to ask you what apps or what kind of workflow to you use to reach your 13W average?

Sorry for all of these questions hahaha.

Sorry I was wrong on this. Listen to what other, more experienced people are saying.

I was rendering in Blender using both the CPU and the GPU and it reached 13 W. However, this is a very rare occurrence - that was once instance out of maybe 5 when I have owned this machine where it has reached 13 W. Normally, when rendering or working with Resolve or Blender, it uses 6-10 W.

 

[doboy]

I'm currently using Apple's 20W charger to run my 14" Pro. No issues with the 20W supporting the computer unless I have accessories attached to USB-C drawing significant power. I mainly use ext SSD or flash drives so they don't have much power draw.