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Old 17-07-2016, 02:13   #1
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Best House battery combinations ?

Option 1: Two 6 volt in series

Option 2: Two 12 volt in parallel

All deep cycle. Both options about same Amp hours. Both taking up same space.

Which option is better and why ?


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Old 17-07-2016, 02:35   #2
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Re: Best House battery combinations ?

Option 2. That way there is at least a chance that if one battery fails the other can be used to provide power.
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Old 17-07-2016, 02:50   #3
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Re: Best House battery combinations ?

In series you get the amp hours of just one of the 6 volters. Eg 110 Ah.

In the 12volt parallel option what do you get ? 110Ah or 110Ah x 2 ?

Not sure of the advantages of TWO 12 volt, apart from post above.


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Old 17-07-2016, 05:08   #4
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Re: Best House battery combinations ?

Option 1# In series there's less chance for mishaps and it's only 6 cells compared to 12 cells of option 2#
There's easy math to compare propability of battery malfunction, Number of cells x number of paralled connections so 1# = 6, 2# = 12x2=24

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Old 17-07-2016, 08:27   #5
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Re: Best House battery combinations ?

Having had one battery (in a group of batteries used to power the house) develop an internal short and go "HOT" on me.....I would strongly suggest the 2-12v battery setup. When our 8-D battery internally shorted, and I finally found it, the surface was so hot I'm convinced I could have fried an egg on it!!! How well do you spell FIRE! But I still had another battery to keep the house powered. I've since redo my entire 12-v scheme, and I now use 6- Trojan T-105s (ea 6-v) organized into 3 12-v "batteries".....lots of redundancy.
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Old 17-07-2016, 08:34   #6
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Re: Best House battery combinations ?

Quote:
Originally Posted by macbeth View Post
Option 1: Two 6 volt in series

Option 2: Two 12 volt in parallel

All deep cycle. Both options about same Amp hours. Both taking up same space.

Which option is better and why ?
Option 1 is the better choice. The 12 volt batteries are only quasi deep cycle.

Golf cart 6 volt batteries are true deep cycle batteries. They have thicker plates and will give up to double the cycles assuming same treatment as the 12 volt batteries.

6 volt golf cart batteries will be 220 to 250 AH depending on brand. To get the same AH in 12 volt will be group 31 or possibly group 27. The golf cart batteries have the same footprint as group 24.
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Old 17-07-2016, 08:50   #7
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Re: Best House battery combinations ?

There is no "best" in boating, as in with most things in life.

There are, however, advantages & disadvantages and Options.

The information given in the responses is correct.

YOU have to make the decision as to what option you are willing to and choose to live with.
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Old 17-07-2016, 08:58   #8
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Re: Best House battery combinations ?

I've installed inverters for 20 years. Tried them all. 31,8d golf cart. Nothing comes close to golf cart battery's.
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Old 17-07-2016, 09:08   #9
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Re: Best House battery combinations ?

Here are my thoughts:

1. With the two six-volt batteries, there is no chance of batteries in parallel discharging into one another and causing a China Syndrome. As has been said, these also tend to be honest, workhorse batteries that are very unlikely to fail except at the end of life, and you would have replaced them by then.

2. If you do parallel your Gr 27 batteries, place terminal fuses at the positive terminals so they will open circuit if one of the cells does fail. The Blue Sea Systems terminal fuses and holders will run you about $30 per battery, and they are available in all sorts of amperage ratings. I used 100A fuses on my three Gr 27 batteries in parallel.

High quality golf cart batteries will out-cycle your 12V batteries by a factor of 2-4, in my experience.

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Old 17-07-2016, 09:16   #10
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Re: Best House battery combinations ?

I'd go with two 6-volt batteries in series, provided they are true deep cycle batteries. See the Compass Marine (aka Maine Sail) discussion about this at www.marinehowto.com Go to the Marine How To selection and then scroll down to find the discussion. Just any 6-volt battery is not even a golf cart battery and most of those aren't really what you need (should have). The Trojan T105's are the gold standard but there are others.

Of course they are more expensive so it is a tradeoff.
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Old 17-07-2016, 09:24   #11
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Re: Best House battery combinations ?

Quote:
Originally Posted by Stu Jackson View Post
There is no "best" in boating, as in with most things in life.

There are, however, advantages & disadvantages and Options.

The information given in the responses is correct.

YOU have to make the decision as to what option you are willing to and choose to live with.
Second this. In boating everything is a compromise.

1. 6V gold cart batteries are more deep cycle than most 12V supposedly deep cycle batteries. Very few if any exceptions. Also cheaper per amp hour capacity.

2. Two 12V batteries in parallel will give you some redundancy in case one batteries dies. Rare but it does happen.

You have to decide based on your style and area of boating which is more important for you.
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Old 17-07-2016, 09:26   #12
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Re: Best House battery combinations ?

Option 3

Before I switched to a 24V DC system, I had (4) six volt batteries wired in series making 2 pairs and then in parallel to make 12V. I had double the amps and in case a battery failed I still had 12 volts.
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Old 17-07-2016, 09:35   #13
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Re: Best House battery combinations ?

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Option 3

Before I switched to a 24V DC system, I had (4) six volt batteries wired in series making 2 pairs and then in parallel to make 12V. I had double the amps and in case a battery failed I still had 12 volts.
That's very true, and a good design.

However, it does not reflect the OP's question.

One could expand this subject by saying: "Hey, OP, NO ONE who "cruises" has only 2 12V or 2 6V batteries on board. If you have any 'systems' on your boat, and if you're not running your boat on oil lamps (!), experience indicates that 400 ah bank is a good starting point. Therefore, (4) six volt batteries wired in series making 2 pairs and then in parallel to make 12V is the BEST choice for longevity, true deep cycle and redundancy."

But that's not what he asked.
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Old 17-07-2016, 10:56   #14
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Re: Best House battery combinations ?

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Originally Posted by Stu Jackson View Post
That's very true, and a good design.

However, it does not reflect the OP's question.

One could expand this subject by saying: "Hey, OP, NO ONE who "cruises" has only 2 12V or 2 6V batteries on board. If you have any 'systems' on your boat, and if you're not running your boat on oil lamps (!), experience indicates that 400 ah bank is a good starting point. Therefore, (4) six volt batteries wired in series making 2 pairs and then in parallel to make 12V is the BEST choice for longevity, true deep cycle and redundancy."

But that's not what he asked.
Stu Jackson,

Thanks for your great insight. I'm guessing you were the best hall monitor in the history of your elementary school :-)

The title of the post is " Best House battery combinations ? " I believe I gave the OP exactly that.
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Old 17-07-2016, 11:44   #15
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Re: Best House battery combinations ?

As someone who used two 12V in parallel for years, I can say that 6V golfcart battery's are WAY better. The 12V deepcycle are really only sort of kind of deep cycle. They don't last as long lifetime wise


Yes you will want at least 4 6V batteries for cruising. Costco's are $90 ish each, though quality varies depending on which coast your on.
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