A battery fed MQTT weatherstation – Arduino, ESP8266, ESP32 & Raspberry Pi stuff
ESP8266 ESP-01 Low Power Mode - run it for months | QuadMeUp
GitHub - frolswe/esp-battery-logger: Simple project for the esp8266 using the power saving features of the chip to test the possibility of battery powered sensors.
ESP8266 Voltage Regulator For LiPo and Li-ion Batteries | Random Nerd Tutorials