Craftsman or Black & Decker 20v battery connector

thingiverse

The contacts used in my final product are 1/2" copper pipe straps flattened and cut in half. Holding them in is an M4*8 screw with a lock nut (it may be a tight fit). Before glueing the top on, insert the soldered contacts and tighten the screws. There is room for 8 AWG wire (what I used) but that is way thicker than it ever needs to be. I recommend 10 to 16 AWG depending on your application.