Looking to install a dual battery bank.

[ShaunTacOps]

Hy Guys,

Boat is a 93 Chaparral 1900SL 4.3L.
I'm looking to install a new sound system. Nothing extravagant just a new blue tooth 4 channel head unit and 4 new 50watt speakers. However I plan on playing the system most of the day while we are out on the water. We spend most of our time just lazing around with about 3 tube runs throughout the day. I just purchased a dual bank switch and was planning on putting in a second of the same battery, a deep cycle marine.

My question comes in with how should I run / start / charge the batteries and do I need anything else? The switch has a bank 1, bank 2, bank 1+2, and off options. I was planning on starting on bank 1 and using bank 2 as a house battery. If I do that do I switch to bank 1+2 to charge them as we go out and about on tube runs and whatnot or should I charge each separately?

Looking for some input!

 

[Crown895]

I have this set up on my boat as well. Its really an either or option, as long as you are properly grounded. You should only have a 65 amp alternator on that boat, but I would be hesitant to run 1+2 on your switch other than in an emergency, like if you ran both batteries down and needed a quick jump. Depending on the switch you have, it may not last for very long if you're using it to charge both batteries while you're running down the water. My advice would be to charge your batteries at the house with an on board battery charger, and enjoy your day at the lake. If you just want to swap batteries occasionally, then most selector switches have a "connect before break" feature, in that you can actually switch batteries when your motor is running, just make sure you DON'T turn it to OFF while running. I run two Optima Blue Tops, with 55Ah rating, and I have yet to run either battery down. And I'm running 4 wake tower speakers, a subwoofer, and 4 deck speakers. I simply float a while, and then run the battery I floated with while we're skiing, and then swap to the other battery to float again. I also installed a switch to just run the 4 deck speakers and kill the tower and sub when we're floating around the old fogies that are used to listening to the AM radios on their boats...lol.

Oh, and one other thing, its very important that you purchase the same size cables that came stock on your boat to wire up the switch. In other words, don't buy 4 gauge if your boat's battery cables are 2 gauge. Enjoy!

 

[ShaunTacOps]

Thanks crowne,

I'm good on the wiring, and the batteries will be wired in parallel so, running them in 1+2 won't cause a voltage issue, and they will be identical so amperage won't be an issue either. I'm just wondering if that will effectively charge them on the 1+2 setting while I'm out riding around? I've heard that will drain power from the good battery equaling out with the drained battery and the alternator will add voltage from there.... Which is not what I want to happen!
Therefore should I use one bank as house start on the other bank and switch back once we get running to charge the house battery up or what?
I've also heard there is some kind of relay that will let you charge both at the same time without draining one into the other does anyone know about that what it is how to install it and what a price on something like that would be?

 

[Silvertip]

You are not wiring the batteries in parallel. You are creating two totally separate 12 volt systems that become a single parallel system ONLY when the switch is set to 1+2 (both). As for one battery draining the other -- that can occur ONLY in the 1+2 position and will not occur with the engine running because both are being charged. Many folks way over-think how to use the switch. Think of it as a traffic cop for the electrical system. When you start the engine, so little juice is taken from the starting battery that it almost becomes a non-issue. A very moderate run on the #1 position would quickly top off that battery. If you anchor for much of the day then switch to #2 (house) for that period. In your situation #2 is the battery that will need the most attention so rather than use 1+2 during your runs, use the #2 position to keep #2 charged or at least keep it from being discharged to the point of potential damage. If your engine is properly tuned and you use the proper starting procedure so the engine starts quickly, it can be started dozens of times before the battery will begin to complain. The battery switch is not a mystery box =-- just use it to send current to the battery that needs the most attention. Only you can determine that. 1+2 is, as was pointed out, primarily an emergency start setting. Yes - it can be used to charge both batteries but why not send the full alternator capability to the battery needing it most. Finally, your system should include an on board charger to keep both batteries topped off at the dock or at home.

 

[Crown895]

Exactly as Silvertip said above. You're simply creating a "blind" so one battery can't see the other one when you install a switch. There shouldn't be a draw from one battery to another when you're on 1 or 2, but 1+2 will allow the weaker of the two to draw voltage from the other. But that stops as soon as the voltages equal. So, if you have one that is 12.7v and another is 12.5v, you can expect them to meet in the middle and stay at 12.6v (thats not an exact, but you get the picture) a static condition. Power may continue to draw to your other electronics, but you'll more than likely stay put provided you don't have a short somewhere.

As for your other question, Blue Sea Systems makes a really good relay setup that does charge each battery according to its needs. Expect to pay for that one though. A manual switch typically sets you back between $40-$60, but a system like that can be around $200-$300 if memory serves. I may be off on that number. I haven't looked at them in a while.