The Jolla phone, which I like because it's an open-source and ad-free platform which will not send all my data to Google, also has a user-replacable battery. Even if spares are rares, batteries made for HTC Desire 210 are a perfect fit and same technology. Having now two batteries, it also allow me to swap for a charged one when the one i'm using is flat. It's much more handy than having a large usb charger connected to the phone when i'm at a event or something. The problem is, swapping the batteries for charging them all with the phone is much less convenient. Especially when you can do only one charge when you are sleeping.. if you have time to sleep. Thus, the necessity of an external battery charger. The battery contacts and charger board are from eBay. If you plan to do something like this, be sure the charger board have compatible electrical properties to the battery you're using. The milling machine only has stepper motors, and is has been equipped with step/dir controllers. These signals (step-clock and direction) are directly generated with a computer running LinuxCNC. That distribution is using a RTAI real-time patched kernel, for minimal step-clock jitter.

The goal : charging a Jolla battery outside of the Jolla phone

Making the basic shapes with Cambam Free

After the configuration of the tools, depths, and other properties, time to generate the tool moves

We can have already in 3D the machine's moves. Now we're exporting a G-Code file...

Before using the G-Code file for real, we can simulate the results with Camotics,
also available for Debian and Ubuntu (.deb package), click here to see it with its user interface.

Meanwhile, i found the _perfect_ battery connectors on eBay

The result, without the battery

Close-up on the electronics part...

Battery voltage vs time while charging


Bonus: Before i've found the battery contacts, i tought about using these pins usually found on "fakir plank", part of the rigging for automated testing of finished printed circuits boards... it would not fit!