my question is how do we stop the charging if not manually ?
i see now, one way would be to make use of the ‘Maximum State of Charge’ value in the Mercedes Me App you can set this to stop charging when the battery has reached a certain %.
to change this to a time period, you will have to calculate how many kWhs will be charged in the time period you want and then convert that to a %, then add that to the current %
this will give you a stop charging time approx near your requirement, but will vary depending on the actual charge being experienced which will vary as the battery is filled.
Another way is to put a timing device between the socket and the 3 pin plug or in the circuit before the socket. Both will need to be rated enough to take the power being used.
The timer could also be controlled from Alexa or Google home Apps to set on/off times - speak to an electrician to get a recommendation