Wiring In Series (pro vs con)

[noelex 77]

In most countries the best "bang for your buck" for a house bank are generic 6v flooded golf cart batteries. The best performing lead acid batteries are the name brand 2v gel batteries. There are many choices between these two extremes.

If you want redundancy with the 2v batteries (this is a good idea, but perhaps not essential given their high reliability), then parallel two banks of 6 batteries. Simple.

When cruising out of the way places if replacement is needed batteries become much more expensive and quality batteries can be difficult to obtain. Even in first world countries be prepared for much higher prices than in the USA.

In remote areas most parts can be imported from overseas reasonably quickly and easily but batteries are usually classified as "hazardous goods". This combined with the high weight creates a lot of difficulties.

These problems mean some cruisers are prepared to pay a reasonably high price for a longer lifespan even if this does not make economic sense in terms of $ per total lifespan AHrs.

There are no universally right or wrong answers.

(Note I have not included some of the latest battery technology such carbon/foam batteries. There is not enough long term experience with these products to form firm conclusions. Lithium is another valid option that rivals 2v gel batteries in terms of reliability, lifespan and cost, but is such different technology that there is a long list of advantages and drawbacks to consider.)

Originally Posted by ramblinrod

Or if one wishes to purchase and install an expensive DC-DC converter, so if a 2 Vdc battery in a series string goes down they can still produce 12 Vdc, they most certainly can. Here's a link to the highest output model produced by Mastervolt..

These 12v/12v converters are not designed to cope with the voltage loss associated with a dropped cell and I don't think they will function satisfactorily in this role.

[ramblinrod]

Originally Posted by TeddyDiver

Don't be naive, nobody saying a couple of batteries parallel are patently unsafe. A bit increased risk, yes. But every battery more in parallel increases the risk and also the consequences if something goes south.
Let's compare presuming the quality of batteries is the same. Series 6 x 2v cells and a one 12v batteries have a risk factor of 1/500 for internal short. Two 12v parallel is 2/500 and six 6/500. You decide what risk you can take and live with it, no problemo.
There are also other risks to consider with paralled strings as uneven resistance which reduces the battery life of all batteries in parallel and then the probality of a fail increases to ^2 with every additional string in parallel.

BR Teddy

IMHO, this post is total BS.

Please cite your references indicating the chances of a battery cell short is 1 in 500.

Artificial numbers produce artificial outcomes.

I absolutely concur that risk increases with every battery added to a house bank.

So naturally, 2 x 6 Vdc batteries carries more risk that a single 12 Vdc battery. Twice the chance of a manufacturing defect. Twice the chance of a failure due to physical damage. The chance of one failing prematurely before the other or rest.

Uneven resistance (impedance actually) does not reduce the life of all batteries in parallel. The battery with the least impedance sees the most service. That's it. So a good (lower impedance) battery, will see more service than less good (higher impedance batteries), causing the impedance of the good battery to increase at a faster rate than if all were as good, balancing the bank out.

The wives tale to always change all batteries in parallel together is ridiculous.

If all batteries are very near end of usable life, and one is really bad, of course, replace all.

But if all other batteries are still "very good", and one needs replacing, replace just the one. That one may not last quite as long as if all others were brand new, but it beats recycling a bunch of "very good" batteries.

This was brought about by folks trying to install a brand new battery in a bank of "already beyond normal service life" batteries. Of course the new battery is going to get used up fast, it's the only one in the set capable of working. If the impedance difference is minimal, the impact is negligible.

In conclusion, there are few energy storage solutions more effective, more affordable, and more safe, than a house bank of 12 Vdc marine Deep Cycle FLA batteries in parallel.

[noelex 77]

Originally Posted by ramblinrod

So naturally, 2 x 6 Vdc batteries carries more risk that a single 12 Vdc battery. Twice the chance of a manufacturing defect. Twice the chance of a failure due to physical damage. The chance of one failing prematurely before the other or rest.

You need to remember a 12v battery is composed of six 2v cells. Essentially it is six batteries connected in series enclosed in one case. 2 x 6v batteries have the same number of cells.

I think reliability and lifespan has more to do with the quality of the construction, robustness of plates etc.

[ramblinrod]

Originally Posted by noelex 77

You need to remember a 12v battery is composed of six 2v cells. Essentially it is six batteries connected in series enclosed in one case. 2 x 6v batteries have the same number of cells.

I think reliability and lifespan has more to do with the quality of the construction, robustness of plates etc.

Fully aware, been discussed in this thread ad infinitum. Exactly my point, artificial numbers produce artificial results. 2x6 Vdc batteries have twice the number of terminal connections and twice the number of cases to go wrong.

The key thing that affects life span is use and abuse. As I have posted throughout this thread, I have yet to see any empirical evidence proving that cheap 6Vdc batteries last one day longer in a marine application, EEE (everything else equal). All we have to suggest this may be so, are lab cycles, which may be totally bogus, and an assumption (and we all know what that does) that lab cycles translate proportionally to real life cycles, and some perception that golf courses have influenced the battery voltage used in golf cars, which in my opinion is not likely the case at all.

The most compelling argument that cheap 6 Vdc batteries last longer is
Dock Speak, and we all know how much science is behind that.

In my experience, (likely more than some and less than others) there is no real difference. (2-4 year average life in either case).

[TeddyDiver]

Rod, there was no time limit neither the environment of installation nor the quality of batteries defined. But the scale is right, ad a zero or two if it makes you happy

BR Teddy

[GrowleyMonster]

2 to 4 years? My $85 golf cart batteries are still going strong after 3 years, no sign of deterioration and in fact they are still performing better, I believe, than when they were brand new. But I will check back into this thread for sure, at the 4 year mark and let you know if they failed or not. I don't think you will get that kind of performance, 10.56kwhr of storage for $680 with any 12v batteries in any combination of series, parallel, parallel/series, series/parallel, counterclockwise, backwards, sideways, or alphabetical order. Just sayin. I'm not even going to touch the disadvantages of parallel wiring. Your mind is made up already and it's just batteries, after all.

[john61ct]

A set of quality true deep cycle batteries, cared for properly, routinely lasts 6-8 years out in the real world, sometimes 10-12.

If you're getting less than that, maybe you're getting ripped off by buying "pseudo deep cycle marine" as is so common with 12V.

But if truly deep cycle, then you're murdering them and should only buy the cheapest ones, Sam's GC2s.

[TeddyDiver]

https://www.google.fi/url?sa=t&sourc...beK1c7XAeqo0gQ

Page 7. The real odds for battery shorts are actually higher. 1/10 for flooded and 1/100 for VRLA. Thermal runaway less than 1/100. These numbers are for individual cells so to be multiplied with the number of cells in the bank. Remember thou that these numbers are for professionally maintained UPS systems. Boat banks in most cases are more prone for premature aging due various reasons so the propability for such numbers is a tad smaller I think.

BR Teddy

[ramblinrod]

Originally Posted by john61ct

A set of quality true deep cycle batteries, cared for properly, routinely lasts 6-8 years out in the real world, sometimes 10-12.

If you're getting less than that, maybe you're getting ripped off by buying "pseudo deep cycle marine" as is so common with 12V.

But if truly deep cycle, then you're murdering them and should only buy the cheapest ones, Sam's GC2s.

Don't be ridiculous. As I stated, on average, cheap
12 Vdc FLA last about as long as cheap 6Vdc. Nobody is getting ripped off, if
the bank costs 1/4 of higher quality batteries that last 4-6 years on average.

So let me explain what average means. One takes the total number of years a set of batteries last, and divides it by the number of that set. AVERAGE. Some will individual batteries will last longer, some will last less. AVERAGE. Anyone can buy higher quality batteries (at any voltage) that will last 10 years. This doesn't make one "special" or a "battery genius". It just means they are willing to spend more money up front for longer life. To some, it may be worth it, for others, not.

But not a single person is getting ripped off. They are getting exactly what they are paying for.

[ramblinrod]

Originally Posted by TeddyDiver

https://www.google.fi/url?sa=t&sourc...beK1c7XAeqo0gQ

Page 7. The real odds for battery shorts are actually higher. 1/10 for flooded and 1/100 for VRLA. Thermal runaway less than 1/100. These numbers are for individual cells so to be multiplied with the number of cells in the bank. Remember thou that these numbers are for professionally maintained UPS systems. Boat banks in most cases are more prone for premature aging due various reasons so the propability for such numbers is a tad smaller I think.

BR Teddy

Thanks for posting the link. Excellent primer on battery degradation cause and effect. Unclear how the specific numbers correlate to marine batteries in marine applications, if at all. For example 10% FLA shorted cells. Not a chance. Don't know where you came up with the 1% thermal run-always, but I know for a
fact that isn't the case in the marine industry or that alone would be my full time job. Instead, I've seen none.

So your opening statement, "The real odds..." I believe to be false.
I think you have drawn incorrect conclusions, due to the unfounded direct correlation between UPS batteries and applications, and marine batteries and
applications which are very clearly, very different.

Again, a great paper, so thanks for posting; just beware how you
apply that information to the marine industry.

[noelex 77]

Originally Posted by ramblinrod

Don't be ridiculous. As I stated, on average, cheap
12 Vdc FLA last about as long as cheap 6Vdc.

A lot of cruisers are convinced that cheap 6v batteries last longer than cheap 12v batteries.

I think this view is reasonable. Not so much because of fundamental differences between the 6v and 12v form factor, but because cheap 6v "golf cart" batteries are built for deep cycle performance. Cheap 12v batteries are more likely to be based on modified starting batteries.

Sometimes the only modification is adding a sticker that says "deep cycle" .

The above comments are of course generalisations. Some 12v batteries have good deep cycle performance. I have had a very long life from good quality 12v gel batteries and will be buying these again, but these are not cheap.

If you are buying cheap flooded batteries my recommendation would be to generally choose 6v batteries over the 12v alternative. I would not guarantee the 6v batteries will be better, but you are swinging the odds in your favour.

[ramblinrod]

Originally Posted by noelex 77

A lot of cruisers are convinced that cheap 6v batteries last longer than cheap 12v batteries.

I think this view is reasonable. Not so much because of fundamental differences between the 6v and 12v form factor, but because cheap 6v "golf cart" batteries are built for deep cycle performance. Cheap 12v batteries are more likely to be based on modified starting batteries.

Sometimes the only modification is adding a sticker that says "deep cycle" .

The above comments are of course generalisations. Some 12v batteries have good deep cycle performance. I have had a very long life from good quality 12v gel batteries and will be buying these again, but these are not cheap.

If you are buying cheap flooded batteries my recommendation would be to generally choose 6v batteries over the 12v alternative. I would not guarantee the 6v batteries will be better, but you are swinging the odds in your favour.

Again 6 Vdc FLA batteries were invented about 150 year ago. They were originally used as auto and farm machinery starting batteries. When golf cars were first invented, these batteries tended to be the basis of design. The other industries switched and standardized on 12 Vdc batteries.

All the dock speak in the world does not verify that they last longer in a marine application ( or even a golf car application), because as we all know, dock speak when it comes to marine batteries is even more worthless as the "what anchor" bandwidth consumed. (At least there is some worthy independent testing for the latter.)

[noelex 77]

Originally Posted by ramblinrod

as we all know, dock speak when it comes to marine batteries is even more worthless as the "what anchor" bandwidth consumed. (At least there is some worthy independent testing for the latter.)

Rod, I disagree. I have always found the opinion of other cruising sailors extremely valuable.

[TeddyDiver]

Originally Posted by ramblinrod

Thanks for posting the link. Excellent primer on battery degradation cause and effect. Unclear how the specific numbers correlate to marine batteries in marine applications, if at all. For example 10% FLA shorted cells. Not a chance. Don't know where you came up with the 1% thermal run-always, but I know for a
fact that isn't the case in the marine industry or that alone would be my full time job. Instead, I've seen none.

So your opening statement, "The real odds..." I believe to be false.
I think you have drawn incorrect conclusions, due to the unfounded direct correlation between UPS batteries and applications, and marine batteries and
applications which are very clearly, very different.

Again, a great paper, so thanks for posting; just beware how you
apply that information to the marine industry.

As I said in the previous post about the difference. Most marine battery banks aren't maintained or cycled as good manner as UPS so they are more prone to ageing before their time ie abusing batteries there's no relevance to any study marine or UPS just premature sulfation or hydroxilization, perhaps both long before there's a danger for internal shorts.
For someone having good practices with their batteries and thus getting longer service life the propability of internal short comes more likely.

BR Teddy

[ramblinrod]

Originally Posted by noelex 77

Rod, I disagree. I have always found the opinion of other cruising sailors extremely valuable.

I agree in a lot of cases, but in almost every case of someone declaring their newest 6 Vdc batteries have lasted significantly longer than the 12 Vdc batteries replaced, with only a couple of probing questions, I find that at the same time they replaced the batteries, they increased capacity 100%, upgraded the charging system, started taking more care not to discharge so deeply, and were more careful to get back up to 100% charge more quickly.

In contrast, when I have personally witnessed a cheap
12 Vdc bank, replaced with a cheap 6Vdc bank, and no other changes in systems or practices, there was no measurable difference in battery life span.

So battery life seems to be subject where dock speak is
Absolutely worthless, as declared in the Mainsail "Deep Cycle"
Battery article, everyone keeps pulling info from to
Support their arguments and absolutely ignoring those
Elements that don't.

Sorry, Keyed
In on Pos iPhone