Power usage - LG 5K UltraFine

Discussion in 'Mac Accessories' started by sammich, Mar 28, 2017.

  1. sammich macrumors 601

    sammich

    Joined:
    Sep 26, 2006
    Location:
    Sarcasmville.
    #1
    Hi all,

    Im a recent owner of a 702 display and just about everything about the display is fantastic, there's just one thing that bothers me right now: idle power.

    Before this monitor, when I wake in the morning, my rMBP (2016, 15") is cold to the touch. If I have the 5K plugged in (as you would), it is extremely warm, bordering on hot. It was definitely asleep as the fans were not running.

    I measured the power at the wall by the display:
    - display standby, no MBP attached: 10W
    - MBP attached, asleep: 45W
    - MBP awake: 80W+

    There's only a USB-C Ethernet dongle and a mouse plugged in to the back of the display.

    The MBP is definitely charged, as it has been plugged in for a while at that point. 45W is how much the MBP draws while it's being used. If you back out the 10W the display uses at idle, that's still 35W being used *somewhere* in the chain.

    Is this what everyone else experiences (warm MBP)? Any ideas on what could be using all that power when the MBP is asleep?

    Thanks!
     
  2. Brookzy macrumors 68040

    Brookzy

    Joined:
    May 30, 2010
    Location:
    UK
    #2
    I must be missing something...

    What's amiss? It takes power to actually turn the screen on. It's a big-ass, 5K, 500 nit screen.

    LG lists its average power draw at 140W:
     
  3. sammich thread starter macrumors 601

    sammich

    Joined:
    Sep 26, 2006
    Location:
    Sarcasmville.
    #3
    Thanks, for not being condescending.

    My query is regarding the other power states (nothing attached, and MBP attached).

    This is a monitor that's basically doing nothing. With no MBP attached, it's drawing 10W. With an MBP attached and asleep it's drawing 45W. The display is practically only supplying trickle power to the minor USB devices and the MBP.

    Since the MBP is so warm, my query is actually more about what the MBP itself is doing differently with the display attached, vs when it's plugged into the normal power adapter.
     
  4. Brookzy macrumors 68040

    Brookzy

    Joined:
    May 30, 2010
    Location:
    UK
    #4
    Ah I see - well the display is in essence a Thunderbolt 3 dock, so with the accessories plugged in I guess everything in the display except the physical panel must be powered up to keep those devices responsive. Does the power draw fall with them unplugged?

    Additionally, if the MBP is warm to the touch, it certainly doesn't appear to really be 'sleeping' - perhaps this is a sleep bug to add to the never-ending list of things that need fixing.

    Personally if I was trying to diagnose this issue I would be looking for software that could 1) keep track of the sleep activity of your MacBook (i.e. when and why it sleeps and wakes - I think this might be possible through Terminal?) and 2) keep track of when the discrete graphics are engaged, to see if it powers down during sleep for example.
     
  5. MrX8503 macrumors 68000

    Joined:
    Sep 19, 2010
    #5
    45w seems really high. I'll have to check mine and if it's that high, I'll have to consider leaving my MacBook unplugged
     
  6. Porkchop Sandwich macrumors member

    Joined:
    Feb 3, 2017
    #6
    "It's a big-ass, 5K, 500 nit screen."

    lol

    Funny this has come up as I noticed this same thing on my s/u just yesterday.
     
  7. sammich thread starter macrumors 601

    sammich

    Joined:
    Sep 26, 2006
    Location:
    Sarcasmville.
    #7
    So, I've spent a little more time gathering unscientific data:
    • without any accessories attached, the display by itself draws 4W
    • with accessories and MBP attached and asleep, it draws about 8W
    • if I 'disturb' the MBP (say, by disconnecting a USB device), and MBP is still 'sleeping' (screen off, no fans, no keyboard backlight), the monitor is measured as using 45-60W for the next few minutes while the MBP 'settles down' (back to 8W). Most of that power is probably the MBP, not the monitor.
    The next couple of tests will be to see if the MBP uses that much power (45-60W) when it's disturbed and only plugged into the laptop charger. The other test will be to try and have the MBP use the power brick for power, while using the monitor's TB3 cable only for data and USB hub.
     
  8. sammich thread starter macrumors 601

    sammich

    Joined:
    Sep 26, 2006
    Location:
    Sarcasmville.
    #8
    It might be that I'm so acutely aware of how the display is being used atm, but I absolutely love it when, after macOS puts screens to sleep, notifications have to display for a brief moment.

    Another observation I made is if I put the display to sleep (ctrl-shift-eject, or via other methods), the power usage is still 80W - the same as if the display is on. I didn't stick around to see how long it stayed at that level. I don't particularly like being cramped under my desk.

    Lastly, overnight, I measured between 12W and 25W of power usage (power meter ticked over 0.2kWhr, so, with rounding in effect, it could've been 0.1-0.2 kWh).
     

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