running MBP with external monitor

Hi guys!

I just bought the new LG IPS 236 monitor to run with my MBP (2009 model).

My aim was to run the MBP with the lid closed so I could save up some space on my desk. I got the wireless keyboard and mouse as well for this.

However, whenever I connect the monitor, and then close my lid, my display switches off as the MBP goes into sleep, then as I wake it up by clicking the mouse, it wakes up but only for a second, and then goes blank again! It writes that it's going into energy saving mode...

Now, the above happens when I don't have my power cable connected. When I'm plugged in, the display wakes up fine and then works.

However, my question is can I somehow do all this without being connected to power?

Thanks!

In my experience you have to have the lid open to use the external monitor, when the power is not connected. Not sure why it's doing this, but my MBP has exactly the same behavior and I'm using an external monitor pretty much all the time.

What I do it to have the power connected, when working. When I'm done I put the MBP to sleep and disconnect the power cord. To continue working I just reconnect power, mouse-click and it wakes up with the video on my external display.

I haven't found a way to get around this - I remember with my iBook years ago there was some third party software I was able to install and use the iBook closed on an external video. Maybe something like that still exists to take advantage of the display when not connected to a power source?

Cheers!

The Apple instructions on operating in Clamshell mode are very clear on this and that is you must be connected to AC power before it will work properly.

The video output and current draw to an external monitor is too much for the MBP to sustain when operating on battery. For more information please see the following Apple KB article: LINK

Hey, thanks for the answer!

Now, at least I know im not the only one like this, and that my new monitor isn't broken (phew!).

You don't have to have the lid open. There are a couple ways of handling the MBP going to sleep when you close the lid. The easiest way is what you're already doing and that's use a wireless or USB-connected mouse to "wake" it. The "trick" is you let it sleep for a good 10 seconds then you wake it up. I went through the same thing and researched it and found that tip somewhere.

There are apps like Caffeine that will keep your Mac always on and never sleep but that's dangerous because you can forget it's on and if you move it, you could damage the drive. It's also not good for it to be running perpetually if there are periods of non-usage like at night when you sleep. Best bet is to keep using the mouse to wake it.