Some gadgets still run on traditional AA batteries, and the ones that do somehow seem like relics of the past. DIYer Davetech over at Instructables shows us how to replace a AA battery compartment with one designed for a rechargeable mobile phone battery.
You don't necessarily need to be an electronics whiz to pull this one off—it's mostly a matter of cutting open your gadget's casing to fit the mobile phone battery, and using an old flash card connector to act as the battery spring. Davetech did have to do some quick soldering in his project, but depending on the parts you use, you may not have to (in fact, I'd try to avoid soldering a lithium-ion battery). When you're done, you should be able to get a much longer charge out of that gadget than you would have with AA batteries. Hit the link for the full instructions.
Modified Mouse Runs on Lithium Ion Cell Phone Battery [Instructables via Hack a Day]