Usually I am really good with this type of stuff. But with all of the work I have been doing to my new boat I have just become mentally exhausted I cannot seem to get a handle on this. First question should be simple to answer. I have a dual 10 amp charger, if I have a battery switch that is left on ALL (Battery 1 & 2 together) and there is a charger lead hooked up to each batter (10amp each lead). Will that cause any issues to the batteries or charger? The batteries are exactly the same.

Now let me describe my current set up, what I have in mind and maybe someone has a better solution.

I have a 30 Concept with dual outboard motors. One each side of the boat there is a standard marine starting battery. Each battery is hooked up to a 1-all-2 switch. On each side it appears #1 is wired to the battery right below the switch. #2 appears to be wired to the battery on the opposite side of the boat. So when each switch is set to #1 the battery on that side is being used to start that motor. When both switches are on ALL both batteries are being used together and when #2 is selected on each switch, the battery on the opposite side of the boat is being used.

What I want to do is add 2 Group 31 House batteries to the mix. I want to mount these two under the Center Console. I want to use these batteries together as one bank (as I have previously on my Velocity) as the house batteries to power the stereo and other stuff when motors aren't running. These two batteries is where I would like to use the dual 10 amp charger.

The first idea I had was to remove both switches currently installed and wire the two starting batteries together (possible with an isolator) and wire them up to post #1 on a battery switch. Take the two Group 31 series batteries and wire them together and to post #2. I want to hook the dual 10 amp charger up to each Group 31 battery. (my concern is since they are wired together (no switch) will that hurt the charger? Maybe install an isolator between each of the house batteries as well?

Leave start batteries and switches as they are. With the new house bank, install them as planned. Put a 1,2, All switch on them. Common to your house bank, 1 to your house load, and 2 going to either of your start batteries for emergency. Leave switch in pos 1. Is charger a simple 5A x 2 bank like the Guest? Most are at that amp. Jump both those output leads together at charger and run 1 lead to your house bank. Jumping the output makes it a single bank 10A charger. Treat your house bank as 1 battery. No isolators. If you want to charge your house bank from the motors, look into the Echo Charge. Similar in workings to the ACRs but get higher marks from the cruisers and sail boaters forums. And they are inexpensive. Not sure of the charging capabilities of outboards. If you want to charge house bank by charger only, forget the echo charger recommendation and just use the switch for emergency

I have been drawing up a very similar method... The charger is a dual 10 amp, so 20 am total, which is what I ned for the two group 31 batteries. I never want to try and charge my house batteries with the Outboard alternators, but would like to be able to use the house batteries to crank them up if needed. I just needed someone to write it out for me to read... I know that sounds weird, but I have been running over it again and again in my head and can't seem to get it out onto paper.

I like your idea, however If I wire the house bank to the common on switch #3, use post 1 to the house load and post 2 going back to the other 2 switches, there isn't a way to play the stereo, etc while the boat is running off of the starting batteries?? I guess the scenario where this would be helpful is if we drain the house bank after all day of radio play, then want to listen to the radio on the way home. If I put the house load on the common, put house bank on 2 and a "jumper" from post 1 back to the other battery switch.

So of using the method you gave me but change to putting the house "load" on the common post as I mentioned above. This should allow me to switch to #1 to start the boat and run with the radio on. When we shut off the motors, switch to #2 which would then switch the house load over to the house batteries. When it is time to head home, go back to #1 thus putting the house load on the starting/running batteries. In the event of "emergency" where the starting batteries are dead, I can switch to "ALL" which should combine house and cranking together (if needed). This would also allow me to use the house bank to start the boat if needed as well. Does this sound right? It just all of a sudden made sense to me, which makes me think it isn't right because I have been struggling to figure it out all damn day.

Yep you got it, for wanting to run stereo off start batteries use common of switch 3 to the house load just as you stated.

Are your existing switches next to each other or on each side of boat?

The existing switches are on each side of the boat right above each battery. For better weight distribution I was going to put the two house batteries under the center console where the fresh water tank currently is. Since I boat in fresh water and don't fish no need for a fresh water rinse... If I need fresh water I can just throw a bucket over the side....

Ok. If side by side I was going to suggest the Blue Seas switch. It replaces both of your switches and also the 2 jumpers from each switch to opposite battery. Less cables, less switches. Very clean and no confusion of what switch to switch to what position.

Yeah I saw those, I might look into extending the cables on one side so I could use that switch... Hmmmmmm decisions...

Got everything wired up Saturday Morning. Works great except the onboard charger that I had took a dump. I swear this new boat is fighting me every step of the way. So next on my shopping list is a new charger. I will buy a three bank charger. (2 banks for the house batteries and 1 bank to charge the starting batteries).

I have a 30a charger in the fountain and a 40a one in the cruiser. Promariner 3 bank. 7-8 yrs now and zero issues. 2 dock buddies replaced their Charles chargers with these also. Best price I found was with Star Marine Depot. Must be mounted in a dry location though.

Why do you want to put 2 charge outputs to the house and not 1 to each start and 1 to house bank? A good charger will send the charge to the needed batteries. Not just a set portion of the output such as your current charger does