How to measure battery charge on Wemos D1 mini?

Question

Arduino

It is necessary to measure the charge of a li-ion battery at 3.7V using the Wemos D1 mini (ESP8266) board.
Help me please)). How can this be done?

Answer 1

If the title of the question is literally fed to Google, then the very first link:
https://www.2ram.ru/video/24/

Answer 2

Required accuracy not specified.
If you need it exactly, then measure the charge (ie, integrate the charge-discharge current at the required time intervals).
If "half-bast" - you can measure the voltage and evaluate the charge according to the typical curve for this type of battery.