Provide a how to find the serial number

[syssi]

$ mosquitto_sub -t '/go-eCharger/+/var' -v              
/go-eCharger/000001/var 11
             ^^^^^^ this is the serial number

[rolandsteinmeyer]

You can simply look it up in the go-e charger app (Title bar)

[Gartenkraftwerk]

You can simply look it up in the go-e charger app (Title bar)

This is not true, if you have renamed the device.

But you can find it under Internet -> Advanced Settings -> Enable MQTT API -> Prefix at the very bottom.