I needed a good 18650 cell holder for some of my projects, so I designed this one and optimized it for 3D printing.

Flip the part over before printing. the 4 squares should be on the bottom. It prints best this way, you can print it with a short support over the bridges if you need to.

I had the best success printing fairly slow, with 3 perimeter layers and with the vase settings. (hollow with a solid bottom)
you will need to play around with the settings a little so they lock and fit together snugly, but this design is far better for 3D printing than trying to copy the plastic injection molded design. the locking tabs on that design are too small to be effectively printed.
I started with that design then rebuild it in SolidWorks, and optimized it for 3D printing.