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I'm using my MacBook Pro like a desktop sometimes. But for some reason, when I unplug the Power Supply, it is impossible. The MacBook Pro immediately shuts off. When I turn it on by hitting any key on the external keyboard, it wakes up for about 10 seconds but then goes to sleep again.

Sometimes I want to use my MacBook Pro without the Power plugged in to it, just to use the Battery a little bit. And also sometimes when someone else needs my Power Supply.

I couldn't find an option in the system preferences. Is there an trick how to get that work?

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Does your macbook work ok without the power supply if you are using it without external monitor/keyboard/mouse? How old is your battery? – Doug Harris May 14 '10 at 18:28
Yes it works perfectly without this. Battery is new. – Another Registered User Jun 15 '10 at 12:43

Here's the solution that worked for me:

  1. Start with MB lid open, native LCD on, connect the external monitor
  2. Close the lid, the computer will go to sleep
  3. Hit a key on the external keyboard/mouse - the computer will wake up temporarily (for ~10 seconds). Here is the trick - before the computer goes back to sleep, open the lid.
  4. The computer will remain awake with the external monitor on, native LCD off, and without power adapter connected.

Tested on MacBookPro5,5 with Mac OS X 10.6.8 (Snow Leopard) installed.

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I found this trick on another site

  1. Open a terminal window
  2. Copy and paste sudo nvram boot-args="iog=0x0" into the terminal
  3. Restart your computer
  4. To revert, just enter sudo nvram -d boot-args and restart

Now you can open the lid without turning on the display on the mac. You can also remove the power adapter!BUT you must open the lid for it to work.

To activate the screen on the mac, close the lid and put the computer to sleep. When you open the lid, the screen will turn on.

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