Where I live, short power cuts are fairly frequent and can be very irritating. I have also wanted to experiment with CCTV for some time. After experimenting with test UPS systems using cheap inverters and old car batteries I decided to scale it up.
When homes have an alarm system installed it usually contains a backup battery in case of power failure. These batteries need to be replaced every few years to ensure the system performs correctly.
The waste batteries are usually sold to scrap dealers for their lead content, but alarm installers are usually happy to give/sell them to you for an incredibly low price. We have picked up 7AH batteries for less than 50p each.
The project was designed, tested and built by myself and Dom.

Check out the video:

A full how-to is availible at http://www.instructables.com/

I am proud to announce that he write up has been featured by the authors of Instructables on their homepage and has also made appearances on Hack A Day and Life Hacker. Gaining the project well over 10 thousand hits (not including hackaday)!

If you like the project please vote for us to win the Green Tech contest on Instructables.com (Vote button in header of page). Thanks!