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

[geohei]

Hi.

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?

Thanks,

 

[geohei]

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?

 

[leman]

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.

 

[geohei]

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.

 

[leman]

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

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

For me, if lid is closed = sleep mode = doing nothing.
I would assume that the machine would generate heat in this case.

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).

 

[Cosmo M3]

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.

 

[buran-energia]

Hi.

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?

Thanks,

Try to shut it down completely as a test.

 

[chrfr]

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?

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

 

[geohei]

...
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).

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.

https://www.howtogeek.com/277742/what-is-power-nap-in-macos/

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.

This was actually when the lid of MBR was closed and the 5K monitor blank. Hence no GPU activity at all since all blank.

Try to shut it down completely as a test.

In this case, the MBP doesn't warm up at all. As expected.

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

You are right. That explains it!

So I can safely leave it connected all the time?
It won't reduce battery life?

 

[chrfr]

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.

https://www.howtogeek.com/277742/what-is-power-nap-in-macos/

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?

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.

 

[geohei]

Just to feedback on this one ... after 2 years, the battery was almost blowing up. The bottom of the MBP seriously arched, almost damaging the inside. I noticed it it could not be put anymore on a flat surface with all 4 protruding edges touching.

Summary ... DO NOT LEAVE THE MBP 24/7 ON SLEEP WHILE CONNECTED TO THE POWER SUPPLY (dedicated power supply or USB-C monitor) !!!

 

[njvm]

Which is exactly what @leman told you 16 months ago!

 

[geohei]

Not exactly. Between ...

its not the best to keep it connected all the time

... and an almost blowing up battery, there's a gap.

Anyway ... my intention was to feedback for users having the same issue/question.
It's confirmed - and it's not only a SHOULD NOT be connected rather than a MUST NOT be connected 24/7.

 

[leman]

Anyway ... my intention was to feedback for users having the same issue/question.
It's confirmed - and it's not only a SHOULD NOT be connected rather than a MUST NOT be connected 24/7.

I don't know if that necessarily follows, after all you have a sample of size one... but yeah, battery health is a valid concern which is why I didn't recommend you to leave it on permanently back then.