The guy mentioned the batteries "didn't hold much of a charge", an understatement if there ever was one as they were absolutely ratted. It didn't worry me much as I figured I had 3 motors to have a bit of fun with.
But then I thought, why not try and see if I can plug the batteries from my good drill into these tools.
Just to put the cart before the horse a bit here, you can see my files at Thingiverse!
Without further ado, here's how I used a 3d printer to up-cycle some old tools and with a bit of work, you can too.
Step 1: How to make a 3d Printed Cordless Drill Battery Adapter
You're going to need a detailed model of your dead batteries, and an idea of how it all goes together.
Mine was held together with a few long screws so it was a simple matter of removing them then breaking a few solder joints. Batteries are dangerous so this step shouldn't be attempted lightly.
I really can't stress this enough. Be VERY careful.