Well, I have a bunch of NiMH (Nickel Metal Hydride) batteries laying around from another project (don't ask). These AA batteries I have came from Amazon.com at $2 bucks, each. I think I bought three dozen to get that price.
Anyway, the four junk NiCd batteries are C size, but only 2/3 height, rated at 1400 mA-h. So, my 2500 mA-h AA batteries are going to be much more capable. Plus, the NiMH have a much better discharge curve that Ni-Cd.
Step 1: Opening Space
Step 2: Solding Together a New Battery Pack & Repacking
Step 3: Short Circuit!
I had just packed the case together - was just driving down the last screw in the case when I noticed it. The handle was warm. In fact, it was starting to get hot. Maybe it was just the left over heat from the glue gun. I had put a little lump of glue inside to hold one of the batteries.
But no, it was getting hotter!
Time to reopen the case again and see what the problem was. Boy, everything looked OK. But, the batteries were smokin hot! Gosh, I hope I didn't hurt them. Eight bucks in batteries down the tubes?
My guess is the solder wick in the middle section got touching. It was just the bottom two batteries that were really hot.
A little anti-static bag cut up made for a good plastic shield. I guess I was lucky the short happened right away. Better to find the short now!
With the plastic shield in-place, I reassembled the case once again.
Step 4: Finished