1. For the 5th cell:
- Soldering iron, or gun (and solder)
- Some sort of quick disconnect that would work with your 18 gauge wire
- Hot glue gun
- Heat shrink tubing (highly recommeded)
2. Rayovac IC-3's are the battery of choice for a lot of people on this site, you need the charger to go with the batteries. RS sells IC-3's under their own brand name (more expensive though). I know that Wal-Mart sells the 4 bank charger, and I think the AAA's (they're pretty hard to find). If you had to, you could buy them online @
www.microcenter.com.
3. I assume you know that RS sells rims. Check out
this site, at the bottom it has the e-mail of a guy selling aluminum rims.