Trouble managing external monitor -- I must be missing something

Discussion in 'MacBook Pro' started by 147798, Jul 13, 2012.

  1. 147798 Suspended

    Dec 29, 2007
    I use a Dell 24" external monitor with my 2009 13" MBP. 75% of the time, my MBP lid is closed, and I'm hooked to power and monitor and ethernet cable. I also use a BT Apple KB and mouse in this configuration.

    Sometimes, though, I'll go work from the couch or something, and everything's unhooked.

    Here's my issue:

    I might drain my battery down to 35% remaining while working on the couch. I don't want to recharge the battery until I drain it completely. Battery management debates aside (i.e. this isn't likely needed anymore, etc.), here's my problem -- when I return to my desk, I want my MBP to run plugged into ethernet and the monitor, with my BT devices, but NOT plugged into power. But I can't get my laptop to wake up and power the external monitor.

    I've tried hitting the return key on the BT keyboard. The external monitor wakes up for a second, I see the screen, then the MBP goes back to sleep. I've tried opening the lid and closing it again really quickly. The MBP just goes to sleep. I've tried opening the lid, allowing it to mirror the screen to the Dell24", then close the lid again. It can run fine on battery power, mirroring the screen, but as soon as I close the lid, the MBP goes to sleep.

    It's like it only has three settings -- plugged into power and powering the external monitor, unplugged and powering the 13" laptop screen, or unplugged and powering the laptop screen mirrored to the Dell.

    How can I get it to run, with lid closed, powering only the larger Dell monitor (I don't want it running the laptop screen because then it drops the resolution of the Dell well below specs, and I don't want a dual screen, because I find that two confusing).

  2. Dangerous Theory macrumors 68000

    Jul 28, 2011
    Li-ion batteries don't like to be discharged, so all you're doing is lessening the battery's life. I don't have the answer to your question that you want, but really it's simply not worth letting the battery drain more than you need to anyway.
  3. 147798 thread starter Suspended

    Dec 29, 2007
    I'll look into that, but I do know that letting the computer run down until it wants to sleep isn't draining it to 0% anyway, as the MBP shuts down before then. But I usually plug it back in around 5%. Maybe it's an irrational habit.
  4. Stetrain macrumors 68040

    Feb 6, 2009
    "Clamshell Mode" (external monitor, laptop closed) only works when connected to the charger.

    You could run in extended desktop mode (dual monitors, no mirroring) which would let your external run at full resolution.

    If you want the external to be the "primary" monitor (with the dock and menu bar on it) just drag the menu bar graphic from the laptop display to the external display in the display preferences:

  5. 147798 thread starter Suspended

    Dec 29, 2007
    Thanks a bunch.

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