ESP32 V3 read battery voltage

How do you read the battery voltage for the new ESP32 V3 boards? Any suggestions are welcome.

WiFi_Kit_series/AnalogRead.ino at master ยท Heltec-Aaron-Lee/WiFi_Kit_series (github.com)

I have seen this code to read analog signals. But which pin is connected to the battery? Pin 1?

Yes, indeed, GPIO1 is ADC pin