Modular 18650 Battery Holder

I recently acquired a couple hundred 18650 lithium ion batteries and I needed a way to mount them for a couple different projects I’m prototyping.

Design requirements:
-No spot welding
-Minimal material needed for print
-Fast, easy print (preferably no supports needed)
-Single object (can be used for + or – side)
-Multiple solder points between adjacent cells for high and even current flow
-Small airgap between batteries for better cooling
-Very modular (can be used in either series or parallel configurations)
-No fine features (I like printing with large nozzles)
-Semi-permanent
-No costly hardware

I did not want to buy any springs because of the quantity needed. A Keystone 209 spring may only be 20 cents, but 400 of them would be more than I paid for all of my batteries. Instead I am using nickel tape (ebay: 7Meters long, 8mm wide, $2.29 total).
For parallel configurations I align all batteries in the same direction and weave 14cm of nickel tape through all of the slots. The ends of the metal tape are soldered to itself. This produces a 1s4p group. Multiple groups can then be soldered together for larger packs.

For serial configurations, the batteries are installed in alternating directions. The bottom bracket uses nickel tape to connect batteries 1 and 2 together, then another piece of nickel to connect batteries 3 and 4 together. The top bracket uses 3 pieces of nickel tape and only batteries 2 and 3 are connected to each other. 1 and 4 are the + and – terminals of the 4s1p configuration.

This is still a work in progress.

To do list:
-Add some sort of interlocking tab/key so parallel groups will slide/snap together
-Design more sizes (3, 5, 6, 7, and 8)
-Design an external cover (or snap-on case) for larger battery packs.