HI,
I've seen a tutorial while ago on the internet about a LiPo buzzer connected with arduino but I
can't find it anymore, so what I'm trying to do is to unsolder a buzzer and solder 2 cables and read them thru (serial monitor) arduino. What is the best way to do that, I mean, add resistor, diode(?) and how to read when the buzzer-(buzz) if is High or Low (as input)?
Does it have to be that buzzer or do you just want to check the voltage of a multi-cell LiPo battery? If the - side of the battery is connected to Arduino ground you can use two resistors as a voltage divider to measure the battery voltage.
First, you need to measure the output signal from the "Driver Chip" that energizes the Buzzer.
Once you know the amplitude of the signal then
you can add a circuit to make the signal compatible with the Arduino.
Until you know something about the output signal
it is not safe to connect this device directly to an Arduino.
A opto-isolator may be a good place to start.