Can I run my MacBook in clamshell mode without being connected to power?

Question

At home, I run my MacBook in clamshell mode (closed lid, external display).

This works fine when you're connected to the power adapter, but it doesn't work when running on battery. That's how it's supposed to be and Apple has some kb entry on the issue. But it's also lame.

You can prevent the machine from sleeping when closed by running InsomniaX, but then it'll assume the builtin display is still active, so you end up with a two-display setup when you really only want the external. This is obviously less than ideal.

So, is there any work around, hack, utility, black magic that I can use to make it run in clamshell mode while strictly on battery power?

Also, bonus points for a solution that makes the AC status not affect the machine state at all. (Like, you know, it does normally, when not in clamshell.)

Answer 1

This page suggests a workaround:

1. Set the display mode to mirroring (use the F7 button).
2. If you haven't done so already, attach the external screen, keyboard and mouse.
3. Press a key on the keyboard (like Shift) and click the mouse once.
4. Close the lid and wait for the Macbook to go to sleep.
5. While sleeping, click the external mouse once, the Macbook will wake up.

If all goes well, the external screen will display the Dock and menu-bar after a few seconds. As soon as you see this, the Apple logo on the Macbook shouldn't light up, open the lid of the Macbook. The Macbook won't go to sleep, won't power up its built-in screen and you can now use clamshell mode in lid-open mode.

EDIT: See comments on this post for kch's experiences with this method.