Drop the battery in the bottom ring then tilt in and snap in place.

Best printed at a 30° slanted angle. No supports needed. 

To that end you can use the version with the slanted edge at the bottom and add just a bit of brim.

Alternatively, use the original without the chamfer, tilt it 30° and add minimal supports at the bottom, so no supports that go up all the way to the top are needed.