There will be series of simple(r) circuits for my new electronic course for elementary school. For start we need power source. Batteries are fine until flattened out, therefore it’s good to have rechargeable one. I took MCP73831T-2ACI/OT, added micro USB connector and switch to select between charge/discharge mode. In the charge mode, the output is connected to +5V input supply. The power is delivered to the charger via micro USB connector, which means eny mobile phone USB supply will do the job. The charge current is limited to 2A and battery cell has integrated protection circuit. I will add 3D printed housing for the complete pack after the testing of first prototypes.
After first prototype I changed PCB a little and assembled final version: