Remote shooting without an AC adapter

I've been hoping to play with some time lapse shots and was wondering if anyone had any expereince with it. Searching the forums for information regarding time lapse or timer controlled remote triggers seemd to pull a lot of threads that aren't what I want.

My main question is what happens if the camera does run out of batteries since I don't have an AC adapter, and I'm more interested in doing landscape time-lapse shots which would make an AC adapter pretty useless.

Any help, advice, pointers or links would definitely be apreciated as I am pretty new to time-lapse, and remote-shooting in general.

Here's my situation: Originally I bought an SD600 without really knowing what I wanted to do with it but now I've found that Canon doesn't offer timer controlled remote switches for this camera, so I'm using my girlfriend's A640 and planning on bringing my laptop and just using the remote-shooting software that's included for now.

Thanks
sorry if this is a repeated question.

I think your laptop's going to run down before your camera. If it goes into "Suspend", you'll lose shooting anyhow. The camera will go a good long while, especially since you don't need the LCD display on. But if the camera batteries run down, it'll just turn off.