ESP32 ADC measurment with variable input voltage?

[jim-p]

@orangedays22

Or is the reference voltage also varying so that it makes it impossible to measure accurately and I have to use option 3?

The ESP32 uses an internal voltage refrence of 1.1V. So if you stay within the recommended operating voltage range, the ADC measurments will be within specs.

LiFePO4 can go as high as 3.65V but if you don't fully charge the battery it should be OK