Bill Porter has written an article detailing the build of his BatBox project:
I had some high energy density batteries lying around and a recent string of power outages have been leaving me in the dark more often than I care for. So in true hacker fashion, I built something: BatBox, just like in Minecraft. My real life version can supply 5V USB power, 12VDC and 110VAC at 240W for about 2 hours. That’s enough to run my dual head desktop 4x longer than it’s current battery backup.
Visit Bill’s website for project details.