NOTE: I wrote this 'ible before I had a comprehensive understanding of electronics. This is a rather bad idea and will most likely wreck your battery. It seemed intelligent at the time. Oh well, live and learn.
Adding a jack to the battery of a cordless tool so you can run it off of wall current and keep it close to full power all the time. This might not be the brightest idea to do with NiCd batteries, but if you have a skunked battery you can't lose much.
I decided to do this project with the Black & Decker Firestorm 18V system, but you could do it with nearly any cordless tool set.
Things you'll need:
-Cordless battery and charging unit
-Soldering iron and solder
-Something to dismantle your battery (In this case Hex wrenches and Torx bits)
-Two wire quick-disconnects (they usually come in male-female pairs)
-Power drill and bit
-Knife or x-acto
You may also want:
-Hot glue gun or epoxy
Step 1: Dismantle Your Battery
-This will void every sort of warranty you could hope to have. Proceed at your own risk
-Discharge your battery before working on it. This should be a no-brainer
Each battery is made differently, so I can't give specific instructions on how to take it apart. Mine involved really annoying hex screws that refused to budge. Then I realized they were Torx - hey this is a learning experience. So I got a Torx10 bit and took it apart.
You should be left with two halves of a case, the cells, and possibly some springy do dads.