Originally Posted by ScottBrownstein
The system sees them as one bank if you select "ALL" on your battery switch, otherwise your system will see them as individual batteries. They are in parallel only through the switch when set to "ALL."
This way of connecting batteries (using a 3 way switch) makes sense in a boat where the second battery is your "spare".
The way most RVs use
their batteries is as one "bank" of cells. Using a 1-2-ALL-OFF switch where 1 and 2 are individual battery supplies, insures that those batteries will never be matched again as one will always be in better health than the other. Better to actually wire them as below and just use the 1 (or 2) connection and save the other terminal for your eventual "solar" connection!
Keeping both batteries wired "as one battery" keeps them charged and discharged as one.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW