I'd like to add a second battery to my existing three battery setup.
Actually it'd be two 6v golf cart batteries wired in series, to be added to
the ships system circuit. I've got a Charles 30 amp AC charger that has 3
circuits; one to each existing battery. There are two engines, each with 70
amp alternators. They're wiring through a Surepower 2 amp, 3 bank battery
isolator.

Can I just add this new bank in parallel to the existing ships system
battery? Do I need to add another isolator? Can I hang that isolator off
the current isolator? As in pull one leg off the existing 2/3 isolator and
split it via another 1/2 isolator. Or do I "have to" use a whole other 2/2
isolator?

Thanks,
-Bill Kearney