I too have the 2015 SS Agile. Your inverter is indeed the Powerstar, here is the manual
I know this because I think it just died....will post another thread!
The manual they gave me when I bought it was for a Tripp-Lite, I was a bit confused.
My Agile does have a propane generator (was an option), solar (which was never originally connected properly). The 2015 did not have the 2nd alternator option.
It also has a battery separator - a separate solenoid to protect the charging system and to assist starting the engine. Others smarter than me should chime in, but my understanding it prevents the chassis batteries from draining the engine battery, but both get charged when engine is running.