I can give an answer but I also have a question.
12 V is normally considered minimum usable voltage or 50
% capacity, but that is always measured "at rest". At rest normally means no charge/discharge for 30 minutes.
I have read several threads Re: auto gen start. On my MH with 4 6V golf cart batteries, starting the Micro thru the inverter will draw 110 amps DC dropping the voltage to 11.5 volts immediately. Of course as soon as I turn off the micro the battery voltage returns to a higher value. Of course my Norcold with two heating elements draws 5 amps AC and 50 amps DC thru the inverter which also causes a substantial voltage drop.
What this means is that the battery voltage might be a poor indicator of when the genny should start. In practice it appears that any time you turn on an AC appliance the genny will start.
I guess if you set 11.5 V as the trigger level you will be safe but if you only have minimal drain on the batteries, the voltage might actually be 11.5 before start which might be to low.
Rereading the above I see I might be creating more confusion than help but possibly more feedback will clear the air.
2002 38' Diplomat
Keith & Shirley