How to power something with 18650 batteries?

Question

Arduino

Good day. I plan to order modules from China: raspberry pi, sensors, holder for 18650, breadboard, esp 1-12. I plan to use the example of all these modules to understand radio electronics, etc.
There was a question about nutrition. I plan to consider the possibility of powering some of the modules from the already existing 4 18650s (without a protection board, there is a good charger for them). I understand that they will need protection against overdischarge, as well as a stabilizer that increases the voltage. Please explain how it works and what is better to take? I also take the MB102 board with the breadboard, with what and how to power it? I would be grateful for detailed answers and links.

Answer 1

I use this and this . If you need more output current then this is

Answer 2

To protect against overdischarge, take such scarves on aliexpress "2s li-ion protection board".
2s means "2 in series". There are also shawls 3s, 4s.
They can charge correctly, which is generally convenient, a simple voltage source is enough. True, it should give out stable 7.4V (for two Li-ion elements).