I know I said I was not going to do this but I stumbled across a harbor freight warrior 18v lithium battery and integrated charger for $16 at harbor freight.  I figured at that price I may as well try and convert my drills to lithium.

Unfortunately these don't pinout the same and it was basically impossible to build an adapter with just the parts I had on hand.  So I had to once again sacrifice one of my old battery packs in the name of science.

I had to cut the pins from the new battery and solder in the connector from the old battery to make it all fit. I also verified while I was at the store that the drill that goes with this battery does not use the temp sense line, so I was fine with just cutting that off and leaving it unconnected.  That has the advantage of making it impossible to accidentally use the old nicad charger on my new lithium pack.

I ended up cutting up a sanding sponge that was headed to the garbage to help take up space in the old pack.  I also hot melt glued the new pack in place.  Finally I drilled holes in the front of the pack to allow for the charging cable to connect.

Buttoning it all up, the charger fits and a quick test in the drill shows that it still runs.  Time will tell if this has enough oomph to run things for a while. It is also outputting 24v when fully charged while the older pack was closer to 18v.  I don't know if that will wear out the drill faster or not.  Still these were basically heading for the bin, so if this works even for a while then it is a win.