Here ya go...from Kisae Customer Service directly...Personally, I think it would be easy enough to just rewire the starter battery to the Ch1 connections if I ever needed to do this...and since the solar side of the Kisae 1250 won't pull more than 30A ever (even if your array was wired for that kind of amperage), the reason for the 50A switch in this diagram is because of the "usual" daily setup where the Kisae could pull up to 50A from the alternator to charge the house...so the design ends up having you search for a large Amperage DPDT switch when the 50A portion isn't really even used for the solar charging of the starter part of the application. To me, this design "works"...but it's a corner case application where I would just "deal with it" when the time came rather than overly complicate the design (though my application is for my young daughter...and maybe I'll talk myself into doing stuff like this "in case")