Stabilizing ADC Readings on ESP32 with LiFePo4 Power Supply for Soil Sensor

Hello,
I need to build a soil moisture sensor for the garden esp32 + micropython, wifi communication - mqtt, >> homeassistant .
Currently working on the power supply, some problems have arisen.
I already have the components, while I don't know how to deal with the effect of the variable power supply from the LiFePo4 (2.5 to 3.65v) on the readings from the adc.
I need to read the voltage of the battery and the soil moisture sensor with the adc.
With variable voltage from the battery, how do I get stable readings from the adc?

The esp32 is directly connected to the LiFePo4!

piotrgl1983 wrote:

esp32 is directly connected to LiFePo4!

.
Rather it shouldn't be (max supply voltage for ESP32 is 3V6). With a fully charged LiFePo4 you may damage the ESP32. Use a Buck-Boost type converter module. There are some such modules on ali - with an input voltage of 2V-5V, they give a stable 3V3 at the output.

Ok, that's my next question, what type will be the most energy efficient, especially as esp32 will be in Deepsleep ?

You can use an inverter module with any of the chips TPS6300x , LTC3113 or MP2155 . The resting currents of these circuits are in the order of 50-100 µA.