TTGO with ESP32 - Measure OWN LiPol battery level

[kapi2454]

Hi to every body, I new in ESP32, come from Arduino, I Start buing a TTGO with OLED (I think that is a normal TFT screen) and BMS for Lithium cell.

I want to know the internal battery V level. I don´t know how can i do thas.
I see a circuit with voltage divider but if I use that, I pass over the bms in charge and discharge.
Existe some fixed V reference for any wher? Like 1V for example?

ThankYou!!