btrayfors, there's no need to wake up at 3AM to manage battery banks if you've been "managing" the power system in the first place. If I'm racing or cruising 24x7, we discuss power management, engine runs, and charging cycles in advance, with an eye towards switching banks optimally and not running the engine when an offwatch might prefer to sleep.
Criticizing the poster rather than contributing to the technical discussion, serves no purpose here. Dave and I can appreciate the concept of discussion without diverting into personal quests or attacks, you're welcome to join us on that level.
Yes, I have redesigned charging systems to match the components, and yes, I have managed energy budgets. Sometimes compromising "whats right" with "what we have to do" and "what we can afford".
But I've yet to hear any reason in favor of parallel batteries, any reason that makes them in any way advantageous to separate batteries, beyond "Well it's cheap and easy to get them that way."
Cheap may be a good reason, but that doesn't make it optimum design practice unless "cheap" is your goal.