NodeMCU ESP8266 http relay control with 12v battery monitor and wifi configuration – Part 1 | Be cheap and DIY:
I made an ESP-01 temperature sensor that sends data to Home Assistant via MQTT. Based on a prototype using a smaller battery I'm hoping it will last 4+ months. : r/esp8266
ESP-01: Reinstalling the Original NodeMCU Firmware (ESP8266) • DIY Projects
Monitoring LiPo battery voltage with Wemos D1 minibattery shield and Thingspeak | Lipo, Lipo battery, Technology
Battery powered #esp8266 logging its battery voltage : r/esp8266
Hack Allows ESP-01 To Go To Deep Sleep | Hackaday
IoT Based Battery Status Monitoring System using ESP8266