MBP permanent USB-C connection to LG Ultrafine 5K monitor

Discussion in 'MacBook Pro' started by geohei, Jun 5, 2019.

  1. geohei, Jun 5, 2019
    Last edited: Jun 5, 2019

    geohei macrumors newbie

    Dec 19, 2009

    I keep my MacbookPro permanently connected via USB-C to my LG Ultrafine 5K monitor. After work is done, I close the lid, and it goes to standby.

    However I noticed, that the laptop is warm (hand warm) all the time.

    - Why is that? It is on standby.
    - Does this hurt the battery?
    - Shall I shut it down preferentially?

  2. geohei thread starter macrumors newbie

    Dec 19, 2009
    I still didn't figure out why the MBP remains warm when lid is closed. It's not doing anything.

    I started now to disconnect the USB-C cable from the MBP. This stops mentioned behavior. It cools down as expected. I can't believe 2 monitor operation is per design required to be physically disconnected when going to sleep.

    Any ideas?
  3. leman macrumors G3

    Oct 14, 2008
    Maybe it's the fact that the power cable is connected? In general, its not the best to keep it connected all the time — the battery power management will ty to keep it healthy still, but its a good idea to give it a bit exercise once in a while. As to the "tepid" MBP — that's not a case for concern at all.
  4. geohei, Aug 14, 2019
    Last edited: Aug 15, 2019

    geohei thread starter macrumors newbie

    Dec 19, 2009
    There is no separate power cable connected to the MBP. It's powered/charged via USB-C (which is connected to the monitor).

    For me, if lid is closed = sleep mode = doing nothing.
    I would assume that the machine would not generate heat in this case.
  5. leman macrumors G3

    Oct 14, 2008
    Thats what I mean. In this case the USB-C connection is the power cable.

    It's not really doing nothing. At very least, it's charging. And modern Macs can do a bunch of things when sleeping and connected to power — backups, mail fetching etc (check out Power Nap).
  6. Cosmo M3 macrumors regular

    Cosmo M3

    Sep 4, 2010
    FYI, MacBook Pros with integrated GPUs (like the 13 inch) will draw more power to drive that 5K monitor. Not to say that the 15 inch with the discrete GPU won’t get warm, but it doesn’t have to work as hard to drive 5K vs. the 13 inch.

    This is normal.
  7. buran-energia macrumors regular

    Oct 9, 2017
    Try to shut it down completely as a test.
  8. chrfr macrumors 604

    Jul 11, 2009
    It's likely that it's Power Nap. When the computer is connected to power, it'll periodically silently wake up to do things like run Time Machine or check for email. https://support.apple.com/HT204032
  9. geohei, Aug 15, 2019
    Last edited: Aug 15, 2019

    geohei thread starter macrumors newbie

    Dec 19, 2009
    Power Nap seems to be the answer to all this. I didn't see the difference between the MBP being connected via USB-C to the 5K monitor versus being disconnected. The link below explains the difference of activity being power connected or on battery.

    This was actually when the lid of MBR was closed and the 5K monitor blank. Hence no GPU activity at all since all blank.
    In this case, the MBP doesn't warm up at all. As expected.
    You are right. That explains it!

    So I can safely leave it connected all the time?
    It won't reduce battery life?
  10. chrfr macrumors 604

    Jul 11, 2009
    By default Power Nap will only run while the computer is connected to power. You can enable it to run on battery power in the Energy Saver system preference.

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9 June 5, 2019