3D Printed Ryobi 18v Battery Topper. Very beginner friendly

This is a 3D Printed attachment for Ryobi 18v batteries. Some very basic soldering lets you connect up to use the batteries to power other DIY projects.

The source file I used (and edited) was https://www.thingiverse.com/thing:410... by rsgeek. Their file was a modified version of https://www.thingiverse.com/thing:123... by Walpeup.

The battery contact springs are Keystone 204 (available from many electronics components places).

To put the battery into "charging mode", I've connected a 10kOhm resistor between Battery positive and the center temperature contact (on the tower) via a switch. Adding the third contact to the 3d design to enable this was difficult since I don't have much experience in 3d modeling, but it works perfectly.

In case you didn't know, Ryobi 18v batteries are fully charged at 21v and "empty" at 15v. So plugging a 19.5v laptop charger into one should be safe as it isn't capable of overcharging it.

My modifications can be downloaded here: https://www.tinkercad.com/things/hXZZ...