Understanding battery charging on new 16" MBP

Hey all
Just received a new M1 Max 16" MBP and it seems to charge with the small power brick (through USB C port) from MacBook Air (M1) work machine I have. It doesn’t charge quickly but that it works surprises me.
Any advice/tips on how to understand power/battery charging limitations for this machine?
Yours in confusion.

Use whatever’s convenient for you. 30W may be a bit too little for an M1 Max machine, especially under load or if you have some other devices plugged in, but generally saying there’s no reason to not use other chargers that you may have.

Just don’t forget that USB-C isn’t magnetic – otherwise the consequences may be grave (if someone trips over the cable).


You could basically use any USB-C charger.

If you use the USB-C brick that comes in the box with the included MagSafe cable, you’ll get fast charging.

If you use the USB-C brick that comes in the box with a normal USB-C cable, you will not get fast charging. USB-C cables don’t support the charging speeds necessary for fast charging the 16" MacBook Pro’s battery, but the MagSafe one isn’t standard USB-C, so it does.

If you use a brick with a lower wattage than the one included in the box, nothing bad will happen to your laptop. It will just charge more slowly. Whether or not this is a problem for you will depend on how much power you are currently drawing from the laptop, but I doubt it would be a problem in most use cases. It’d just be slow.

(This is basically the same equation you can apply to phone chargers too, at least when it comes to charging speeds.)


Thanks both. That’s really clear. I will indeed be using the machine under considerable load at times (After Effects with chunky chunky files) so am curious if it can hold its charge with small brick. But mostly it’ll be on the MagSafe.

does anyone know whether fast charging is bad for the battery on the long run?

In theory, fast charging is “bad.” But using your battery is also bad for the battery, keeping it plugged in all the time is bad for the battery, and putting the laptop in a closet with an empty battery is also bad for the battery. Lithium ion batteries have reached a state where they’ll last a long time regardless of how we use them.

love this. all states = bad for battery.
thanks @snelly

Happy to provide cynicism any time it’s needed!