Summary

Components you will need: 12x18650 cells, BMS preferably over 20A, power bank module(link in the description), cables that can withstand over 10Amps
(the BMS is optional as the power bank module already has one, but i don't trust it)

First you'll need to print "18650_support.stl" and "18650_wall_support.stl"
After you have printed the models for the cells of the power bank you will need to weld the cells in the following configuration: 4s 3p; 3s 4p; 6s 2p; (mine is 4s 3p) you can also solder the cells if you don't have a welder, but i don't recommend doing so.
There is a free space for a BMS on the front of the battery pack if you decide to include one.
I have secured the power bank with double sided gecko tape (this can be done after you have printed the casing to ensure it fits right)

After you have made the power pack you'll need to print the "powerbank_base_v2.stl" and "powerbank_cap_v2.stl" if you decide that the decorating shapes and the writing don't suit you you can open the project in blender and disable the booleans corresponding to them.

the parts should not be printed with raft because it won't look good.
On the base of the case i have included supports only on the ports and the writing on the bottom (depends on the printer).

link to the power bank module used: https://a.aliexpress.com/_ExcY1VW
Be careful if you search for other offer as there is another module that loos similar but has some extra ports.

If you have any questions regarding the project you can reach me at Denislavnikolov006@gmail.com and I'll be happy to help