[MrForbes]

We got a new Lithium battery powered cordless drill in 2008, and it worked ok for a couple years, then quit charging. Last week I figured I'd give it a try...and it showed that it was charging. Huh. Having a mysterious battery system that sometimes works, and sometimes doesn't work, is probably not the best thing for our robots.

Lead acid batteries (like we use) are pretty forgiving, very powerful, relatively inexpensive, etc. They're not high tech and not modern, but they are the best solution for the problem of powering our robots.