I was wondering if it was possible to measure the voltage of a battery that will be powering my Arduino Pro Mini in my upcoming portable project. The reason being is that even though my battery is protected with a TP4056 along with the protection circuit built-into the battery, I wanted to be able to see the voltage on an OLED to make sure everything is working correct.
I have seen people use an analog pin to read a battery voltage, but in most cases, the Arduino was powered by a different power source than the battery it was powering. I have a 3.7V, 1700 maH battery connected to a MT3608 boost converter which powers my board with 5V (the battery is attached to a protection board). Obviously, connecting the boosted output of the converter to m y board would be pointless, but since a LiPo has a maximum voltage of 4.2 volts, can I connect it to an analog pin to measure the voltage?
I know that some sensors exist to measure voltage, but I really can't buy extra stuff for this, I would like it to work without any additional components (also, sticking a massive sensor doesn't seem ideal for my project). My Arduino Pro Mini is a 5V board, just in case that helps
If it is possible, I would love some insight on how to do it!