Hopefully some 12V warrior has some thoughts on this!

I'm thinking about replacing the batteries on my Cobalt 323 this spring and since it's been freezing and snow covered here i've been thinking more about doing a larger upgrade. Current 12v system includes 3 batteries ( interstate group 24), 3 battery switches (4 way 1, 2, 1+2, off), 1 Blue Sea ACR, Generator (Kohler 5e), and a Charles 3 bank battery charger. Engines are 496 Mag HO 65 amp alternators on each and the kohler 5e puts out about 25 amps from its charging system.

I have realized that i really have no idea how these are all wired together so i have reached out to Cobalt to see if I can get a drawing or schematic to see how all of this works together and what I think I could do to upgrade the system, I talked to customer service but haven't got any drawings yet. Worst case i'll just start following the wires to see where everything goes. For the upgrades i'm generally thinking about going with 3 AGM group 27 batteries probably Odyssey. new smart charger probably Blue Sea P12 7531, 2 Blue Sea 7610 Si-ACR's, possibly changing the switches out to Blue Sea 5511e (off-on-combine) (this would require some rewiring of the switches and allow battery combining but eliminate the ability to isolate a single battery which I think it does now) (probably mitigate concerns about battery isolation by using high quality batteries). The switch change just makes everything easier to understand as the 4 way switches are mass confusion and in a situation where i needed to actually combine or isolate batteries i don't want to have to read a wiring diagram to figure out how to configure the switches. although if i do this right it should just be on or off 99% of the time.

Concerns:

1. The generator and both engines all have alternators/charging systems that would/could feed charge to the batteries all at the same time if all were running. At minimum both engines would be charging at the same time if the generator was off. ACR's would combine the batteries but I believe this is all ok as each of the alternators would self regulate their output. Correct?

2. If running the generator and charger at the same time would the generator DC output through its alternator/charging system interfere with the P12 charger if running the P12 charger from the generator AC output? The Si-ACR's have a disconnect feature controlled by the P12 charger which would force disconnect the port and starboard batteries from the generator charging system but still output from the p12 to the batteries directly, but the house/generator battery would get both inputs and may fight with each other and never really charge this battery?

3. Maybe just only use the charger on shore power? This eliminates #2 above and would allow the generator to feed alternator charge to all 3 batteries through the ACR's while at anchor on generator power?

4. Switch configuration when running, coving out, shore power?

5. Want to make sure i don't run down the starting batteries if hanging out on battery power only. (again i think the ACR's would take care of this by disconnecting the port and starboard batteries as the voltage began to drop) Right?

6. What am i not thinking about?

Our primary use is cruising as well as coving out. When hanging out on the water we run the stereo system, fridge and A/C so usually fire up the generator for that. or sometimes just hang out and run stereo only no generator just battery power.

The bordem of winter always leads to me spending $$$! At worst something to think about!

current battery switches. Not my actual boat (this one is filthy) but a pic of the same panel I have which I found online.





Rough drawing of possible layout based somewhat on what i think is there and how i might configure it.




Detail of battery/ACR/charger connections

I think most modern boats have Isolators that take care of the multiple charge inputs and all new chargers are solid state and can cut off if needed. Do you keep your boat hooked to shore power?
I can recommend this brand. I have 2 larger versions of this one on a 50ft express cruiser..
I have 2 engines , a generator, and 2 chargers. One charger feeds the house bank which I have lithiums on. The other charger feeds a battery bank for each engine and also feeds a battery bank for a bow thruster.

Chris

Not really able to follow your drawing, but there are no signal wires coming from a charger that connect to the ACR

Drawing I made up some time ago has Alternator output connected at the Battery but can also have it connected at the switch. The issue which can cause an issue with it at the switch is if switch disconnects when motor is running. This can blow the ALT

Once one motor starts and charges that Bat, the ACR will connect to House Bat and start charging it.

There is a relay which combine house with start Bat if needed, but can also place it between the 2 start bats instead. By pushing a momentary on switch at the helm their cobined

I do not keep the boat connected to shore power long term. When I am at the lake i may leave it on overnight to run the charger but generally if I'm not there i don't leave it connected. Just always made me paranoid since i did have a Charles charger boil over a battery one time and that was not fun.

I think this drawing may be a little dated. The Blue Sea P-12 charger when used with the Blue Sea SI-ACR does have a Start Interrupt signal wire that can be connected between the charger and the ACR to force the ACR open to separate the batteries when the charger is operating to allow the independent charging of each battery. Also the SI-ACR does allow current flow from A-B and from B-A so it would connect and charge in either direction based on which battery is getting charging power. I think this would eliminate the need for the momentary switch and have it happening automatically at the battery. The swithes I'm thinking of using are the 2 circuit (off-on-combine) switches so i can do the battery combining at the switch by using the combine setting on any 2 switches that i would want to connect together.

Yes, the ACR does have the start isolation circuit, but never heard or seen anything at Blue sea or other which would say can be used long term

No, that will not happen, but please talk to Blue sea
ACR is set up to disconnect if any Bat drops below 12.7V for 30 seconds. Now the ACR is not designed to be able to be a pass thru for starting current, only charge current.

Follow up, a NEW fully charged Lead Acid Bat is 12.7V, so if one of the Bats is old or has been drained just a little, like from a stereo, then ACR will not connect

This was from the manual on the P-12 charger

Charger will work, good deal
Good luck with everything else

I think that may have came across as me trying to argue about this but i'm really trying to think through this and understand what I'm doing. I appreciate you bringing up things to consider as I'm really trying to see if I've thought through this. I appreciate any input on this