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I have an external Sonnet box https://www.sonnetstore.com/products/egfx-breakaway-box-550, and it is not charging my notebook fast enough, e.g battery still draining when the MacBook screen is open. Especially with docker and compiling and IPad as an external display. When the screen is closed, all good enough, e.g 3-4 powers of gaming until the battery is 0. Power draining proof

I tried to plug in external power adapter (native) when eGPU is powered, but MAC does not switch to it, despite Apple states, that it will use a source with the most power.

However, if I change the order of load, e.g. plug power first, then Sonnet, then the battery is charging from the native adapter and all good.

Still, it is sad that need two cables and eGPU is not powering enough

Is there any way to fix it? Maybe to switch power read from another source? E.g. some command in terminal to use the specific USB-C port for power or whatever?

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  • Can you use a powered hub and connect the Sonnet to that?
    – Mast
    Oct 15 '20 at 7:34
  • @Mast As far I understand, external eGPU boxes (e.g. Sonnet) provide power and eGPU graphics data flow in a single cable and it is not designed to be connected via an intermediate hub.
    – auraz
    Oct 15 '20 at 9:48
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If you have a new box that you're still able to return, you could consider buying the 650 model instead of 550 model that you currently have. The 650 models supports charging the laptop with up to 100 watts, whereas the 550 model only supports 87 watts.

In regards to switching power source and your comment regarding that you think Apple incorrectly states that the source with the most power is used:

The 2018 version of the 15" MacBook Pro comes with a 87 watts charger. So it is actually rates to supply the same amount of power as your Sonnet box. Therefore I don't think you can expect the laptop to switch to it when you connect it.

It is only the newer models from 2019 and on that comes with a 96 watts charger.

You could consider buying the newer 96 watts MacBook Pro charger to ensure more power is supplied to the laptop, but you'll still have to plug in two cables this way.

There's no command in Terminal that allows you to choose a different power source for charging.

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  • Thank you for your answer. Just to be clear, when I connect first native charger, and Sonnet after that, power is enough, but not vice versa and not only Sonnet. I will look forward to changing power supply inside the box.
    – auraz
    Oct 15 '20 at 9:50
  • I think the problem is that the Sonnet box communicates to the computer that it supports 20V charging up to 4.35A - but in reality it is not able to supply that much power (probably because the GPU is using a lot of power). The laptop cannot know this when you connect the cable.
    – jksoegaard
    Oct 15 '20 at 9:57

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