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here is my situation:

  • my screen is plugged into a USB-C port, and can charge my 15-inch 2017 MacBook Pro, but can't actually supply enough power during periods of intense usage.
  • my USB-C power adaptor can supply enough power, so I'd like to use that instead.

However: plugging in the screen, then plugging in the power adaptor has no effect on power delivery (checked using a USB-C PD debugger dongle: it's at 5V and supplies 0A.)

Unplugging the screen, plugging in the power adaptor, then plugging the screen back in does work (I get 19-20V 2.9A from the adaptor). But it's annoying, and easy to forget (especially since I don't keep the PD debugger dongle in the loop the entire time, and it's hard to tell when it's in the correct state).

So: Is there a way I can force getting USB-C power from another port without physically unplugging things? Trigger some sort of reevaluation of the connected devices to have the system select the best power source again, instead of sticking with the first one it found?

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  • Very interesting. My MacBook Pro 15" 2017 automatically switches to the higher powered input no matter what the usage is as far as I can tell from short testing.
    – X_841
    Jan 17, 2022 at 21:35
  • What monitor? Does it have a setting to disable the charging?
    – Gilby
    Jan 18, 2022 at 1:03
  • I'm not sure I understand what you are doing here. Are you connecting the power supply to the display then connecting the display to the Mac? That might not supply more power to the Mac than the display would provide alone because USB-C devices are not all built to pass power through. Macs will automatically draw power from the most powerful supply connected. If both the display and power supply are connected directly to the Mac, and the power supply is more powerful then the Mac should draw power from the power supply. If it is not doing that then look into broken hardware.
    – MacGuffin
    Jan 18, 2022 at 22:34

1 Answer 1

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Unfortunately no, there's no way to trigger such a reevaluation from software in macOS.

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