3 batteries wired to dual battery switch-gctid368374

[Guest]

I was thinking of putting 2 batteries wired in parallel to Batt1 and the other single battery to Batt2 on the dual battery switch. That way when anchored, we can use Batt1 to run the stereo (twice as long, due to the 2 batteries in parallel) and still have the fresh unused battery to start with on Batt2 or start with switch set to BOTH.

Does this make sense to anyone else or anyone have any experience with that kind of setup? I'm new to boating, so this seems to make sense to me, but looking for any real world input before giving this a try.

[2850Bounty]

It makes total sense, but I'd reverse your #1 and #2 banks regarding the MBSS terminals.

#1 is usually synonymous with 1 battery..... or your start battery.

#2 is synonymous with 2 or more batteries, such as a bank of multiples Deep Cycle batteries.

This makes it easy to remember which bank is which.

Other than that, I'd say this is what you will want to do and is what many of us have also done.

Some of us have gone to 6 volt Deep Cycle Golf Cart batteries, cabled in series, groups of two.

This gives you 12 volts, and generally more Amp Hours..... which is what you want for your HLBB (house load battery bank).

.

[CaptTom]

As for #1 or #2 having a standard meaning, I can't say. My #1 is the house bank, and where I normally keep the switch. #2 is a reserve starting battery. Normally I just look at the labels I put next to the numbers: "House" and "Starting". That way there's no confusion.

If you're doing two batteries in parallel, buy them both at the same time, don't try to mix different models and vintages.

I think everyone here probably knows this, but for the record you want to use deep cycle batteries, not automotive style starting batteries, for your house bank. Starting batteries (or even cheap "dual use" marine batteries) will have a very short life if you discharge them even half way more than a few times.

Finally, two 6V golf cart batteries in series can give you more usable amp-hours in a smaller space, and for less money, than two 12V in parallel. And they're made to withstand lots of deep cycles.

Once you start looking at deep cycle batteries, you'll find they're rated in amp-hours, not just cold-cranking amps. A lot has been written about how to estimate how many amp-hours you'll need, so I won't repeat it all here. Rule of thumb is never deplete your house bank to less than 50% of capacity.

[2850Bounty]

CaptTom wrote:
1.... As for #1 or #2 having a standard meaning, I can't say. My #1 is the house bank, and where I normally keep the switch. #2 is a reserve starting battery. Normally I just look at the labels I put next to the numbers: "House" and "Starting". That way there's no confusion.

2... If you're doing two batteries in parallel, buy them both at the same time, don't try to mix different models and vintages.

3.... Once you start looking at deep cycle batteries, you'll find they're rated in amp-hours, not just cold-cranking amps. A lot has been written about how to estimate how many amp-hours you'll need, so I won't repeat it all here. Rule of thumb is never deplete your house bank to less than 50% of capacity.

1.... Tom, you are correct! I doubt that other than here on the BOC, anyone really qualifies the the MBSS as to a correlation between #1 and #2.......... and there certainly are no rules. Do what works for you!

2... Yep...., "like" batteries at the same time, and Deep Cycle batteries.

3... another great point, and a perfect excuse for purchasing one of the Xantrex LINK systems that track Amp Hours in/out.





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[Guest]

A couple of things you may want to think about. Charging the two batteries wired in parallel will take longer. If using a generator you will have to run it longer and deal with the noise longer. If using the alternator you will have to run the boat engine longer. You could just buy a deep cycle battery with a larger capacity than the one you have. For running just a stereo I think 3 batteries are overkill.

Matt

[2850Bounty]

Matt.... Amp Hours are Amp Hours.

The Amp Hours that we consume, must be replenished..... and the sooner the better!

Charging time frame will be very close to the same whether one large battery, or two smaller batteries given Apples to Apples on Amp Hour consumption.

It's well cell battery chemistry!

The beauty of two 6 volt GC Deep Cycle batteries is the added Amp Hour capacity.

When the capacity is greater to begin with, the daily use and typical rate of discharge will likely be less.

Excessive rates of discharge is what adds to shorter battery life span.

.

[Guest]

I have just this setup on my boat. One regular starting battery on position 1 on the battery selector, and two deep cycles in parallell on position 2. I bought the two deep cycles from Sams Club back in 2006 (Energizer house brand, made by Johnson Controls) and they have performed extremely well. I am charging on shore power at the slip, and I have a Balmar 100 amp alternator with an external voltage regulator, so it doesn't take too long to get these up to capacity while running for extended periods. The deep cycles were bought together, share the same date of manufacture code, and have been in parallell all their lives, so I keep them that way in the winter and top off the charge periodically when they're not on the boat(unlike some members here, I take them home to a nice warm basement in the winter.) Last summer unbeknownst to me, the power went off on the dock for 5 days. Those two deep cycles kept the refrigerator running all week, and it was in the high 70's and low 80's the entire time. This will be year 6 on them, and my starting battery is 8, they both still hold a charge well. We'll see how long they keep going....and going....

[Guest]

2850Bounty wrote:
Matt.... Amp Hours are Amp Hours.

The Amp Hours that we consume, must be replenished..... and the sooner the better!

Charging time frame will be very close to the same whether one large battery, or two smaller batteries given Apples to Apples on Amp Hour consumption.

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I agree with you Rick. My point was that by increasing the AH capacity with the three batteries, charge time would be longer with the increased capacity than without it.(Something to think about.) It just seems to me that for running a stereo, (quote from original post "That way when anchored, we can use Batt1 to run the stereo (twice as long, due to the 2 batteries in parallel) and still have the fresh unused battery to start with on Batt2 or start with switch set to BOTH" ) unless there are amplifiers involved, a larger AH battery than already installed as the house battery would be much easier to install (just drop it in) and more cost effective than adding an additional third battery. Now if he were running other large accessories along with the stereo thats a different story.

Matt

[2850Bounty]

Matt, let's create a hypothetical scenario;

Ya got two large water tanks.

A 200 gallon tank, and a 400 gallon tank.

You use 40 gallons from each (well above 50% depletion), and you put 40 gallons back into each.

Given that each fill neck is the same diameter, which tank took longer for the 40 gallons to go back in?

[Guest]

The few preceding posts, and subsequent posts, will be more than you need to know about batteries.

Luckily, the OP's question was answered early, and the rest is because they are bored. :ign-

We return you to your regularly scheduled battery thread tangent.

[Guest]

Thanks to all that replied and for the additional info. As an FYI, all three batteries are marine deep cycle and the two I was planning on wiring in parallel are the same make/model/age.

[2850Bounty]

The two Deep Cycles are great for the HLBB, but you'll do much better if #1 is a cranking battery, IMO.

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