I've printed quite a few other single cell holder, but all of them left something to be desired. The ones with 3d spring either doesn't have enough force or its will get weaker with use. Some use hardware that's hard / troublesome to source if you just want a few holders.

For this design my goals are:

• Strong electrical contact without spring
• Easy to assembly without fiddling with wires through some small holes
• Use common and easy to source hardware
• Easy to print and customize to provide holder for all possible cell sizes

The hardware you need for this is minimal:

• 2 Nickel strip of 8mm or 7mm width, cut to length
• 2 M3 nuts
• 2 M3 bolt, 10mm to 15mm would be appropriate

To assemble, put your Nickel strip into the terminal plate, then bend it to the side that have a pimple (not the side with hole), then bend it once more and put it through the hole of the holder. Now, put your M3 nuts to the captive nuts hole on top of the holder and screw your M3 screw in. Repeat for the other side. Now, after you put your battery cell in the holder, use a screw driver to tighten one of the screws to make good contact with the cell and loosen it when you want to remove. When tighten, screw will push directly into the part of nickel strip you inserted, so you can tighten it without worrying about breaking fragile plastic parts. After assembly, nickel strips and bolts are all connected to your battery so you can use either but Nickel strips can carry much more current from how it's connected.