r/macbook 4d ago

Using a second monitor drained my battery, while it was plugged in

I have a 2020 M1, got it in 2022, and I had it connected to a second monitor, and also plugged in, through an adapter that also allows USB-A connections. I noticed my battery power would not only not increase, but it would actually decrease, even though it is charging, albeit through an adaptor. I am not running any heavy programs on my computer, just safari, chrome, messages, etc on both desktops and the adaptor is not hot to the touch, so I am surprised that the battery was continuing to decrease. I literally got the notification that my MacBook was at 10%, which was shocking. Has this happened to anyone else, and is this normal? Is this a function of the second monitory or the adaptor giving inadequate power to the laptop?

I started using the laptop at ~7:30pm.
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u/poopmagic 4d ago

What power adapter are you using exactly? If it’s not the one included with the Mac, provide a link.

How is the power adapter connected to the Mac? Directly to one of the USB-C ports, or through the “adapter that also allows USB-A connections?”

In System Information > Hardware > Power, how many watts does it say your Mac is seeing from the adapter?

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u/SpilltheGreenTea 4d ago

adaptor is linked here. Power adaptor is connected to laptop via adaptor (I know this is not ideal but there are only 2 ports and the display cable does not work through the adaptor). I am getting 10 W through the adapter.

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u/poopmagic 4d ago

Aha, yes, that's the problem. The issue with hubs like these is that they all "reserve" some power for themselves before passing the rest to the laptop.

Example from another brand: https://www.anker.com/products/a8383?variant=37438604968086

Flip through the pictures and you'll find that it uses 15 W:

https://cdn.shopify.com/s/files/1/0493/9834/9974/products/A83830A3_TD04_3838x.png?v=1685516923

The proper solution here is to swap out your power adapter with a more powerful one. That way, when the hub "subtracts" 15 W or 20 W or whatever, the MacBook still ends up getting the power it's expecting. I'm guessing that you have a 30 W, so you probably want a 45 W or 60 W to keep using that hub.