Originally Posted by Peter B
Except I guess, when like many on here I suspect, I doubt it is the perfect solution when you only have one alternator and several house and a separate starter batt..?
I wired to the battery switch post #1, which then runs to the battery and can't be switched off. If you have too many banks, use a relay.
I have twin engines, 2 alternators, 2 banks. My relay is a simple continuous duty 90 amp relay wired through a manual switch and the fuel pump relay on the engine started by the one starter battery I share between both engines. So the relay joins both starter and house banks together. You really only need one starter battery for both engines.
So when the engine starts and the manual switch is on, the relay closes and the alternator charges both banks. Since the starter bank is never flat, it is just like starting the other motor with alternator that charges the house bank made of 2 batteries. So then both alternators when both engines run share the load and it takes the heavy load off just one alternator which makes charging more efficient and extends the life of the alternator charging the depleted house bank.
I have 2 battery switches that have those 3 posts and 1 continuous duty relay.
If my starter battery went flat, I can rotate switch to All on battery switch to send power from house bank to start bank, and can also run my gen to power the cattery charger. And I can isolate my starter battery by rotating the battery switch to number 2position.
Here was my drawn out diagram when I was conceptualizing this
So two changesI made, the relay goes between the 2 switches and I moved house bank battery # 2 to post #2 which allows for it to be isolated if desired.
I run the boat with switch powering the starter bank on #1 and switch running house bank on ALL (1 + 2), and the manual switch for the relay is always on.
Another advantage I can not turn off the connection from the AC charger to the batteries.
(I can turn off the AC charger switch on the charger)
So when I plug in I know If I have AC shore power, my batteries are being charged.
I also have a 2 pole DPDT AC relay that connects directly from shore to the charger.
The AC power that comes in past the twin 30 amp main breakers before the AC panel provides power to that relay. If AC shore power is unplugged, the relay de-energizes and the AC charger automatically is connected to the generator.
I actually also designed an automatic transfer switch using two 4PDT 35 amp power relays, So when I return to shore power, when I plug in the boat powers up without me having to manually move any switch.