Power Adapter Compatibility

[feelyat]

I've got two 14" MBPs I use regularly. One a personal M1 Pro, and one M3 Max that I use for work. They came with two different power adapters, 67w for the M1 and 96w for the M3. Can either be used on either device? Are there any repercussions of using a lower wattage power adapter other than charge speed?

Here's why I ask: in the past, a family member had a 2015 MBP (15" i7) that had came with an 85w Magsafe 2 adapter. At some point, the adapter died (probably at the cable) and he replaced it with a 45w adapter. It "worked" in the sense that it appeared to charge the battery, but (according to a knowledgable macbook repair shop) caused the battery to fail prematurely. I don't want that to happen to my M3 if I happen to plug it into the smaller charger. Does Apple state anywhere that it's safe to use a different power adapter than what comes with the laptop? What about 3rd-party adapters?

 

[chabig]

Can either be used on either device?

Yes. You can use them interchangeably, without repercussions. If you were to measure the length of time each takes to charge your machine, you might notice that the 96W adapter charges faster. But it's likely you won't notice in ordinary use.

 

[feelyat]

Heh...I just found my answer on Apple's support page (https://support.apple.com/en-us/109509):

If your Mac uses USB-C to charge, you can charge your Mac laptop with any USB-C power adapter or display. You can safely use a power adapter or display with higher or lower wattage than the adapter included with your Mac. For the best charging experience, you should use the power adapter and cable included with your MacBook Air, MacBook Pro, or MacBook.

That seems definitive.

 

[feelyat]

Yes. You can use them interchangeably, without repercussions. If you were to measure the length of time each takes to charge your machine, you might notice that the 96W adapter charges faster. But it's likely you won't notice in ordinary use.

Charge time is rarely something I'm worried about. Now that I know that it's fully safe, I might take advantage of that fact and use the smaller (and lighter) adapter for travel, regardless of which laptop I'm traveling with. Or I could just get another adapter to keep in my bag.

 

[msackey]

It "worked" in the sense that it appeared to charge the battery, but (according to a knowledgable macbook repair shop) caused the battery to fail prematurely.

Hmm, I find that repair shop's assessment to be incorrect. If there is not enough charge provided by the adapter, it simply won't charge the battery and just provide power to run the laptop. When the laptop is not actively used (i.e., asleep), there should be then enough juice to charge the battery.

 

[feelyat]

Hmm, I find that repair shop's assessment to be incorrect. If there is not enough charge provided by the adapter, it simply won't charge the battery and just provide power to run the laptop. When the laptop is not actively used (i.e., asleep), there should be then enough juice to charge the battery.

The problem was that the laptop was rarely used without power and that it spent months (years) streaming audio (classical music) at all hours of the day and night. So the battery never got fully charged, and never got a chance to discharge. It’s hard to say if the usage pattern was more of a problem than the charger, but I think both contributed.

 

[iMacDragon]

The idle consumption of the arm macs is so low that practically any usb c charger will eventually charge up even if lightly using, I think even 20w iphone charger eventually would unless screen quite bright.

 

[msackey]

The problem was that the laptop was rarely used without power and that it spent months (years) streaming audio (classical music) at all hours of the day and night. So the battery never got fully charged, and never got a chance to discharge. It’s hard to say if the usage pattern was more of a problem than the charger, but I think both contributed.

If the laptop spent years being used, of course the battery wore out even when plugged in. Not unusual.

 

[HDFan]

that practically any usb c charger will eventually charge up even if lightly using,

from a quality manufacturer. Cheap chargers can be disasterous.

 

[iMacDragon]

from a quality manufacturer. Cheap chargers can be disasterous.

True enough, that is general advice for any charger really, not worth skimping to get cheapest no name for almost anything for safety reasons.