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I just received a new 15 inch macbook pro (2019). I connected it to my external monitor LG 38WK95C-W via the monitor's provided USB-C cable.

It does video/data transfer however since it is a usb-c cable it is also charging my MacBook. I did some research and these are the specs for both my LG monitor and my MacBook:

There is no feature to disable power via USB-C cable, under the circumstances will my LG monitor damage MacBook's battery since it provides less Watts (60 W) than MacBook's charger (87 W)?

Also any tips / workarounds to have the USB-C connection only transfer video without providing power?

Thank you for any assistance.

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    I'm trying to find some resources to help you. Unfortunately no good news so far :( . Try this and this for some (annoying) workarounds – Max Coplan Sep 20 at 23:41
  • Thanks Max, yeah I read these before but as you said they are annoying workarounds indeed. – shadesco Sep 21 at 0:06
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I'm assuming the main concern you have is that charging from the LG 38WK95C-W display is going to damage your MacBook Pro in some way.

This is not something you need to worry about. Having a charging source that provides 60W is really akin to using one of the chargers that ship with the 13" versions of the MacBook Pro on a 15" MacBook Pro. The net result is that your MBP will charge slower than it would with the higher watt charger, but this will not cause any damage to the MacBook Pro.

If you're concerned about this (and you really shouldn't be) you can change the cabling you're using to connect to the display so that you're using one of the display's other ports (e.g. it has HDMI) and totally bypass the USB-C port so that power pass-through doesn't occur. Of course, to do this you'll need a USB-C > HDMI adapter.

  • I thought that it would charge slower, but since it is expensive machinery didn't wanna take chances and thought of asking. I have two questions with regards to your feedback: What happens when charging is full but you are still connected to display, any negative effects? If I used a USB-C > HDMI adapter, won't the image quality decrease? – shadesco Sep 21 at 0:05
  • The MBP will regulate charging so that's not a concern - think of it like having your MBP plugged into its AC charger all the time, or an iPhone left on charge when its battery is full. As for your resolution, despite its size your display has a maximum resolution of 3840x1600. Since this falls within the HDMI spec, I assume you'd still get the maximum resolution. – Monomeeth Sep 21 at 0:12
  • Thanks makes sense. Btw what happens if without focusing you get both monitor and Mac charger connected, both will be charging at same time? – shadesco Sep 21 at 3:11
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    No, the MBP will only take a charge from one AC source at a time, so using multiple power supplies does not speed up charging. If you do connect multiple power supplies, the one that provides the most power will be used. And, before you ask, it doesn't matter what order you connect the power supplies. :) – Monomeeth Sep 21 at 3:27
  • Thanks that was helpful, cheers – shadesco Sep 21 at 13:08

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