This is a little analog battery monitor for my sump pump system that has a DC battery backup. It uses a Wemos D1 ESP8266 dev board, OLED display, breakout board for wiring.

I added a 1.5Mohm resistor in line with the analog input, the D1 already has a 220k ohm resister in series with a 100k ohm resistor to divide a 3.3V signal down to 0-1V. The 1.5Mohm resistor increases the division so that a 15V input is around 0.9V at the A0 pin.

I use ESPHome with Home Assistant to link data from the esp8266 into HA. My ESPHome code is here in my github. For the sake of posterity I included it in the docs folder in this repo.

2022/11/22 - Initial upload

HiLetgo 0.66 inch OLED 0.66" OLED Mini OLED Shield with I2C/IIC 64x48 Pixels 3.3V

Ximimark 5Sets WeMos D1 Mini Prototype Board XD-08 ProtoBoard Shield Double Sided Perf Board for Arduino

Autocad Fusion 360

Ultimaker Cura 4.12.1

• Printer: Creality CR6 SE

• Layer Height: 0.2mm

• Infill Density: 20%

• Infill Pattern: Grid

• Filament: Inland PETG+ 1.75mm White

• Material: PETG

• Print Temperature: 235 degrees C