Well, you don't really 3D print the entire battery tester. That would be neat though. This is a actually a 3D-printed casing for the ZB206 battery capacity tester . What you do print is an integrated battery holder (rubber-band-powered) that can hold an AAA, AA or 18650 battery for testing. So it is easy to pop in any of those batteries and begin testing its capacity immediately. The ZB206 is mounted to the casing using 4 M3 x 6mm screws. There are 4 bolts that come with the board. I repurposed 2 of them as battery terminals, as shown in the photo. You can find the OpenSCAD source file and STL file on Thingiverse . ZB206 usage instructions: If battery meter beeps on power on, press the [SK] button. Press [SK-] and [SK+] buttons to set the discharge current. For NiMH AA batteries, use ~0.5A. For 18650 cells, you can go as high as 1.5A depending on the cell condition. Press [SK] button to start the testing process. When the battery meter beeps. th...