I did this here
Although is was fun to do, it was too hard to do to make it worth while
It doesn’t make any economic sense and is dangerous
The new drills are cheap, powerful and charge up fast
Sorry to say, that old drill is just not worth anything to you. I just went thru all of this. I hung on to my old drills for several years even though I had no batteries
I finally donated them to a local charity and they were very happy to get them
I felt bad because I finally decided they were worthless. It was only then that I decided to donate them. Not exactly philanthropic of me, was it?