large alternator is used to
charge the batteries as quickly as possible. Quite a different scenario
than a Toyota or a Greyhound.

Maybe differrent than a toyota, but not a greyhound, or fire and emergency
equipent.

Battery isolaters and a/or a DUVAC system work very nicely.

The isolator will seperate the cabin battery[s] from the engine battery[s] and
you can use the same charging system for both and have them seperated at the
same time.