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Old 09-08-2013, 09:23   #31
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Re: 12v vs 6v House Bank

The capacity, or AHrs, will not be same for the same physical sized 6v and 12v battery.
The 6v battery will be roughly double the capacity of the same sized 12v battery.

In other words the the battery bank will be roughly the same physical size for the same capacity and voltage.

Making a 12v battery bank out multiple 12v batteries, or 6v batteries will make little difference to size.

Generally 2v batteries are better quality deep cycle batteries than similar 6v batteries which in turn are better than 12v. These are general rules that are only applicable to similar brands and types of batteries. The rule usually hold true, but does not mean there are not good quality 12v batteries available.
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Old 09-08-2013, 10:00   #32
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Re: 12v vs 6v House Bank

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Originally Posted by MarkJ View Post
Not true in many, many installations.

Many new boats finding the batteries is a half day exercise in destroying the aft cabin.

To get at mine you must remove all the bedding and both mattresses from the aft cabin - and that cabin is the 'garage' so I have to remove all the junk as well.

Batteries are only easy to care for if they are checkable without fuss. So easy they can be checked often whist cruising.

So for people thinking about it look to see how easy it is to jump in there and top up some water on a weekly basis.


Mark-- My experience is that properly charged batteries... by that I mean charging with a modern multi state charger including my solar charger, DOES NOT CAUSE THE ACID/WATER TO BOIL OUT. I find the same with my cars. Heck, Wifey's Chrysler Sebring convertible one needs to remove a tire just to get at the battery.

Yes, in days of the old resonant transformer chargers, batteries required constant attention.

Maine Sail has it RIGHT!!!
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Old 09-08-2013, 16:39   #33
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Re: 12v vs 6v House Bank

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6volt vs 12v house bank. I read 2 6volt is better than 1 12v. but would (2) 6 volt be better than 2 12v in a house bank. Cost, size, weight not withstanding. It would seem 12 v would be better if amps are same?
sailor0516
(battery novice)
Battery 101.

1. Series.

If you connect two batteries in series then the voltage adds up but the amp hour capacity stays the same.

Series means in line or first battery negative goes to the boat ground, positive goes to the negative of the second battery. Positive of the second battery goes to the boat system positive. OR you could say: boat ground to B1 black. B1 red to B2 black. B2 red to boat positive.

So two 225 amp hour, 6 volt batteries in series would give you 225 amp hours at 12 volts.

2. Parallel

Two batteries in parallel the amp hours will add up but the voltage will stay the same.

So two 225 amp hour, 6 volt batteries in parallel will give you 450 amp hours but still only 6 volts.

So 12 V is not inherently better if the amps are the same. Typically two 6 volt batteries of a size equal to one larger 12 volt battery will have more amp hours. Usually cheaper, usually sturdier, certainly easier to carry around.
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Old 19-08-2013, 06:08   #34
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Re: 12v vs 6v House Bank

I am of the opinion that no marine battery will last longer that 3 years on a Cruising Sailboat. Including the more expensive ones. There are always the exceptions to this and these are the Batteries we all would like to know about. 6 volt wet cell Trojan batteries are popular and often called best bang for the buck. Rolls 6 v wet cell batteries often called the best, but more expensive.
The very expensive Odyssey Marine Batteries are very expensive and well advertized.
Sears diehard marine batteries are made by Odyssey and have Sears 3 year warranty. Small money in comparison.

Feed back welcome. Looking to buy my new housebank battery. Lifeline also very highly praised in user feedback.

Which MAKE AND MODEL NUMBER would you buy for your housebank ( 800 + to 1200 AH ) any why. I would like to know the best and the best acceptable charging procedure, Charger Amp output. Solar trickle charge setup.
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Old 19-08-2013, 06:13   #35
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Re: 12v vs 6v House Bank

Three years max doesn't sound right. I think Maine Sail and many other members here have described their battery life as being in the 8-10 year range?

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Old 19-08-2013, 06:24   #36
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Re: 12v vs 6v House Bank

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Three years max doesn't sound right. I think Maine Sail and many other members here have described their battery life as being in the 8-10 year range?

-Chris
I think 8-10 is the max possible but many cruisers report 5-7 years. If you only get 3 years from a bank of new batteries you had a defective lot or seriously abused and neglected the batteries.

As mentioned in this and several other threads a 6 V, deep cycle FLA (flooded lead acid) battery, often sold cheaply for golf carts and other non-marine applications are the best bang for the buck. With minimal care you should see that 5-7 years or better life.

1. Keep them charged as high as possible as often as possible.
2. Don't discharge them below 50% capacity
3. Use a smart charger and periodically plug into shore power and run an equalization cycle.
4. Keep them topped off with water.

Some will recommend AGM batteries but they are much more expensive and generally more sensitive to charging issues which can lead to early failure. The main benefit is you can charge them much faster than a FLA battery but if you can't keep them topped off most of the time they may die and early death.
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Old 19-08-2013, 06:37   #37
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Re: 12v vs 6v House Bank

+1

You should expect 5-7 years. Just changed out my 7+ year old Trojans which had begun to lose capacity.

Bill
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Old 19-08-2013, 06:51   #38
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Re: 12v vs 6v House Bank

Hiya Skip! I second your thread! ++

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Old 19-08-2013, 06:54   #39
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Re: 12v vs 6v House Bank

One might/should expect 5-7 years or whatever, however knowing the vagaries of cruising its probably a great idea to budget and plan for a shorter life expectancy.

If I had 5 year old batteries on board now I wouldn't be heading into the Pacific for 2 years without funds budgeted to replace the batteries in some small and expensive island in the middle of nowhere.

Mine are 2 years old but they are much older than 2/7ths of their life span. (and they have never been below 50% but it would be so easy to do so when off the boat for a day or two and something screws up)



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