If you've ever had the misfortune of losing power right in the middle of a big project you know the headache that can come with that. Over on Instructables, ooda55 guides you through the process of building your own battery backup system so you never lose a minute of work.
In ooda55's project, the goal is to create backup power for a security system, but you can apply the guide to any gadget you don't want to lose power. The backup uses a bunch of cheap batteries they gathered up from an alarm installation company, a sine wave inverter, some wire, earth blocks, relays, plugs and a socket.
Since you're working with electrical power this project isn't for the faint of heart, but the Instructable is very detailed and walks you through the process carefully. If you're not hooking it up to a security system you can stop after step seven. Head over to Instructables for the full guide, diagrams, and video.