The factory converter has worked well for us in 1200 days camping, often on extended external power. It provides excellent power to our 12v
system but the single stage charger can overcharge our batteries. Or so the forum (usually) tells us.
So we disconnect it with the switch and let the factory solar maintain the batteries. It's not the best charger either, but does turn itself off when the batteries reach (near) full charge. The converter/charger does not shut off, it just keeps on charging at full voltage.
I replaced the factory converter/charger because we upgraded our battery and solar system and my aging mind may forget the switching routine of the Battery Disconnect Switch. I don't want to damage these expensive new batteries, or break camp for travel with no 12 vdc to the fridge.