The Arduino Nano is then covered by the glue to avoid the possible short circuit.

Do the same for the other modules.

Then simply tied them with hot melt adhesive. Before that you can cut off some pins on the modules to save space, such as arduino Nano's ICSP pins. Once the work is completed, this Nano is impossible to use again, so, for those unused IO pins, cut them off!

Program to the Nano, and test the functions. Test the charging effect. After doing the above work, this stuff can be put aside.