LiIon 12V battery. Schematic and model of housing.

Sometimes you go to the flea market and spend some amount of money on some scrap. After you get back home you start thinking of what to do with all these things you have bought. The same happened to me: I have bought batteries for some unknown portable device. There were four 3.7V 3100 mAh cells. Unfortunately one of them was completely dead. Fortunately, three cells is enough for building the pretty powerful yet small rechargeable battery providing 12 volts.



The schematic is pretty simple and is shown in the picture. The minimal voltage is 3x3.7=11.1V, the maximal - 3x4.2=12.6V. Pretty enough, huh?

In order to make everything up and running, you just have to wire all the cells and carefully solder the wires to the controller board. The P+ and P- terminals are connected to the input socket used for attaching the 12V adapter (for charging) and two banana type connector for the load. A small switch is used to cut off the output socket from the battery (to prevent occasional short circuit). To control the voltage I use the tiny voltmeter. To put everything together I designed the 3D model of the compartment, big enough to fit all the cells, controller and required controls. This is the screenshot of the OpenScad window. As you can see, there is a lot of holes for controls: voltmeter, switch, 12V input socket, 12V banana type connectors.

If you are interested in the model, you can find it in my repository on GitHub. There is some number of primitives as well as complex things like the box I used as the base for this compartment. The address of the repository is the following: https://github.com/ut8uu/3d_models

You even can play with the 3D-view of the finished model. Just follow this link - the GitHub knows how to display STL files.

At the moment my 3D printer is out of order so that the next part of the post containing pictures of the ready-to-go box as well as assembling steps will be slightly later, as soon as I fix the printer (this is one of the tasks I enumerated in my ToDo list).

To be continued...