Boat "House-Battery Bank" Monitor

The batteries on my boat seem to be failing. I decided to monitor the voltage to see how it is doing. I have 8 each 6 volt golf-cart deep cycle batteries wired series-parallel to give 12volts with 880 Amp-hours. But 2 have a shorted cell and are disconnected.

They are usually charged by 4 each 150 watt solar panels connected to 2 each 30 amp MPPT solar controllers. Also sometimes large frame alternators on the main engine or the diesel powered watermaker.

Anyway, the monitor is a Wemos D1 Mini with an ADS1115 4 channel A to D to measure the battery voltage. The 12volts (11.9 to 14.4) is outside the normal range of the ASD1115 so there is a resistor voltage divider implemented as a trimpot to set the voltage below the max allowed.

Also there is a cheap 3.3v buck converter on the board.

Once a minute it measures the battery (supply) voltage and sends to to node-red via mosquitto MQTT. It also checks for an OTA update each cycle.

The code is available on my GitHub: https://github.com/svkatielee/ESP8266_Arduino_projects