UPDATE 23APR18: I WILL BE DISCONTINUING UPDATES FOR THIS PROJECT FOR THE TIME BEING. Please check out Rocket Box!
UPDATE 03MAR18: Collar reinforcement V4.5
In my initial tests the collar worked out well. I printed a large batch of 40 last night and noticed the collars were separating from the bases (using PETG). It may just be that my printer needed to be re-calibrated. So I've decided to make some small changes to widen and reinforce this area. One note for those of you who are printing these, the inside diameter (ID) of the collar is designed at 18.4mm in Fusion360. When I print on my machine they are measuring around 18.0mm - 18.1mm ID. For me this works well with regards to the 18650's i'm using. If however you are noticing an issue with ID being too large or small, please send me a message and I will be sure to upload a couple of versions for you to try that will make allowance for these differences. I appreciate feedback on how the design is working for you!
UPDATE 02MAR18: STL issue.
I found an error in the uploaded STL that may cause your slicer to not recognize the collar on the cell cap. I've made a correction and uploaded again. Should now work.
UPDATE 01MAR18: Final Fix?
I did several revisions today and came up with version 4.4. It's tolerances are tighter and keep a firm grip on the batteries. I also included a wrench to help remove cell caps when replacing batteries. I added a collar to help stabilize the individual cells. New flex contacts should help resolve inconsistent terminal connections. I'm using PETG because my application requires the batteries to be used outside in the warm weather. PLA should work for indoor use or cooler weather. Feel free to leave comments or questions.
UPDATE 26FEB18: Inconsistent Contact
I've been experimenting with large packs and am getting inconsistent contact with the batteries. I'm now looking into buying some leaf spring connectors and doing another redesign. If you've got some ideas please let me know!
UPDATE 18FEB18: Lock Plate
I've just uploaded Version 1.0 of the lock plate. It press snaps in place and helps bring a more rigid finish to battery packs. Experiment to see what works best for your project. if you plan to use your batteries on devices that may cause vibration I would still recommend shrink wrapping the pack. Keep an eye open for more revisions.
UPDATE 18FEB18: Version 4.0
I made some needed modifications to the interlocking. this update includes 2 full length interlocks. Makes for a much more rigid pack. The thin sleeve from previous version 1.1 has been removed from the design. To interlock you will probably need to hammer each piece together to make them flush. In my next update I will be adding bracing for battery packs that will ensure they maintain positive contact with the battery terminals. More soon!
UPDATE 20OCT17: Version 1.1
I was attempting to assemble several lines of cells this morning and was finding the interlock was just too tight. So I've made some minor corrections to alleviate the issue.
If you're interested in building a solder-less battery pack using 18650 lithium cells this project is for you. I wanted to build a clean pack that is easier to disassemble with less risk of ruining batteries due to incorrect soldering practices. Two caps are required for each cell. They will interlock together to form a brick style battery. Using stainless steel 10mm M3 nuts, bolts and washer you can build any configuration you wish. All without the use of soldering tools. The cost per cap is approximately $0.07 and weight is around 2 grams.
These have been designed to create a gap between each cell to allow proper airflow. the interlock has very tight tolerances. If you decide to print a copy first start with two and ensure they lock together evenly using your printer.
After assembly use zip ties to ensure they stay together and keep contact with each post (M3 bolt).
My next plan will be to create post caps to protect against potential arcing.