Report the status of the battery bank from the Victron battery monitor to thingspeak. Hardware needed is ESP8266 module and 3.3 volt regulator. Nothing fancy in schematics, just get a ESP8266 running, connect GPIO16 to RESET so it can wake up from deep sleep, connect Victron TX+GND to RX+GND on ESP.
Im using BMV-702 and a simple 3g/wifi router to make my yacht report battery status.
Example thingspeak page: https://thingspeak.com/channels/91575
Connector on BMV-702 (VE.Direct) is JST-PH: https://www.sparkfun.com/products/9916
Pinout on VE.Direct:
- 3.3 volt (I dont dare using this to power the ESP8266, tell me if you tried! :-)
- TX
- RX
- GND