Recommend PETG for elasticity, ease of print, chemical resistance, strong interlayer adhesion.

Supports are needed for batterystalk.stl and celllid.stl only. Remember to orient all the other parts in a reasonable manner as they are not necessarily oriented correctly in the STL files (sorry!)

Post processing: remove supports and the small breakaway support cylinder from cap.stl using small flat screwdriver.

Orientation doesn't matter at this point but if you can make it look like what i have in the photo, that will work well. Note that the top sprint strip is one connected strip even though it doesn't look like it in the photo (it will connect two AAs together). If you are using an alternative connection method, the spring's flex distance should be about 3mm. I know the connector pictured is not ideal, but what can I say, it's a hack, not NASA-approved. FYI the sprint strip came from a retracting cord lanyard. Hot melt glue gun was used here.

Desolder the contacts from the stalk of the old battery pack, but leave some wiring attached so we can reuse them. The salvaged contacts should look like in the picture below (the thick black wires are original, the blue wire is my addition).

Recycle the old NiCd cells.

This forms the AA cell block.

Try to press the nuts so they bottom out and fit snugly and are held in place by friction. You can use a long M3 bolt to thread it through the hole and pull it tight from the other side.

This is how the final assembly should look without the batterystalk.stl, to demonstrate where parts go:

This is how you should actually assemble it:

Be careful not to push on the bolts or they will dislodge the nuts. Thread carefully! Do each bolt a little at a time and do it upside-down so gravity helps to hold the nuts in place. Result should look like this:

Note the middle contact is not actually necessary and we are including it only for completeness or in case we decide to upgrade the battery pack to support for multiple speeds in the future. The orientation also doesn't matter since the drill will just spin the opposite direction if you reverse it.

Once the contacts are in place, push it all down so everything lines up, especially the 3mm hole for the bolt.

Again, be careful threading the bolt not to push the nut out of its pocket. It's a pain to reinstall it because you'll have to remove everything to get at it. I prefer just turning the bolt and letting the threads advance the bolt to catch the nut.

Ain't she a beaut!