Have two 502MPIs, dual battery switches (choose 1, 2, both or off) and a battery on port and starboard side. Anyone have a diagram of how these are usually wired up? I did figure that the port side switch is feeding the cabin 12v power (its powered up if that switch is on 1 2 or both)

Im adding a bank of 2 group 31 AGM batteries in the galley as house batteries, and think I need to pull the feed off that port switch and run that end into the house battery bank. Then run the dual bank in parralel to the port side battery with a battery switch in between them, so they are only connected when the system is charging

https://www.perko.com/images/catalog...(8500INS1).pdf

Are you talking about having 4 batteries and the cabin electrics all being fed by the port side alternator?

No, under way both switches in the bilge would be in the BOTH position, everything connected, two alt charging all four batteries. When docked over night or what have you, then only the two house batteries would be used, or if I put the port switch on #1 battery then those 3 would be tied together if more reserve was needed. Kill all those, can switch to #2 on each engine and start them up