6 volt batteries

Neddy
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Re: 6 volt batteries

Postby Neddy » Mon Oct 19, 2015 8:01 am

Naki585 wrote:This is from a well respected caravan builder in Australia.

I think he should now be referred to as a formerly well respected caravan builder!

On that website the original query (2x 6v or 1x 12v) was quite well answered by "Camnwen" :-
"A 6V battery is 3 cells, a 12 V battery is 6 cells. Two 6 v batteries in series will give you the same voltage and A/H capacity as a 12 V battery of the same A/h capacity. If the pricing, size etc is right, it should not make any difference if you use one 12V battery or two 6V batteries."

Pretty much exactly the same as my reply.

Neville.

Teardrop

Re: 6 volt batteries

Postby Teardrop » Mon Oct 19, 2015 8:42 am

But the more common iteration is two 12 volt batteries in parallel as opposed to 2 x 6 volt batteries in series. This is because battery slideouts and battery locations tend to lend themselves more to twin battery arrangements, as opposed to one huge 12 volt battery which people will struggle to lift or move.

The comments on the Bushtracker site jogged some distant memory and I suspect there may be some theoretical merit to that point of view - if you are comparing 2 x 6 volt in series to 2 x 12 volt in parallel. However, capacity is based on the surface area of exposed plates because that area is where the electrons will transfer through the electrolyte. Longevity and ability to deep discharge is more on the depth of the plates. Therefore, using the same theory, a deep cycle battery with its thicker plates should be harder to charge than an equivalent starting battery. Has anyone noticed the difference? I haven't.

So while I would not rubbish what has been said, I would not agree that there is any practical difference at all. In fact, there are other technical reasons that could point to 2 x 6 volt batteries in series being more efficient to charge than 2 x 12 volt in parallel. But again, would anyone notice the difference?

Bushtracker is pushing a perspective, and one that includes lithium. I don't see any need to rubbish them for that.

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Re: 6 volt batteries

Postby scubadoo » Mon Oct 19, 2015 9:18 am

Bushtracker - Site Admin from that link says - whatever this means:
"The problem is those batteries will burn too much solar power to excite them enough to begin accepting a charge, called "warming the plates"."

I still say not only 100% gobbledegook but total BS and not even worth consideration.

We all now know that Mr. Bushtracker says that "6 volt golf cart style deep cycle batteries" can't possibly ever be charged from solar panels because those batteries are not exciting enough for him and they will burn. Tui!.
You definitely must warm the plates first or is that cool them?

I don't think Naki585 mentioned "6 volt golf cart style deep cycle batteries".
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Re: 6 volt batteries

Postby mattn » Mon Oct 19, 2015 9:43 am

As I read it, he is bagging all Lead Acid based system, not just 2x6V. MrBushtracker is pedalling the Lithium Battery bandwagon, my guess would be because the significant benefit of Lithium is to his bottom line.
Don't be alarmed when you see me talking to myself, I am getting expert advice.

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Re: 6 volt batteries

Postby Neddy » Mon Oct 19, 2015 9:46 am

Teardrop wrote:The more common iteration is two 12 volt batteries in parallel. Dene
Maybe, maybe not - but either way that is not what is under discussion here.

Teardrop wrote:"Battery slideouts and battery locations tend to lend themselves more to twin battery arrangements, as opposed to one huge 12 volt battery which people will struggle to lift or move."
Exactly. That's precisely why so many people use 2x 6v batteries in series rather than a single 12v battery.
The original poster had said "I have read that 2 x 6 volt batteries in series is not a good idea."
What he read was of course absolute twaddle.
2 x 6 volt batteries in series provide an excellent basis for any 12 volt system.

The question of 2x 6v batteries in series or 1x 12v is no big deal. Either way :-
The charging efficiency is exactly the same.
The cost is essentially the same.
The weight is essentially the same.
The capacity is exactly the same.
Battery longevity is exactly the same.
Charging regimes are exactly the same.
Discharge current capacity is exactly the same.

Take away the BS and there is nothing to discuss!

Teardrop

Re: 6 volt batteries

Postby Teardrop » Mon Oct 19, 2015 10:54 am

Neddy wrote:Exactly. That's precisely why so many people use 2x 6v batteries in series rather than a single 12v battery.


Actually, I think you will find that more systems have 2 x 12 volts in parallel than one huge 12 volt battery.

Neddy wrote:Maybe, maybe not - but either way that is not what is under discussion here.


Actually, it is what is under discussion here - you choose to use the less common single 12 volt battery as your comparison, because the answer will differ if you use the common 2 x 12 volt parallel system.

Neddy wrote:What he read was of course absolute twaddle.


What you forgot to add is, "In my opinion".

Lets just look at a bit of theory here. The battery when charged has one plate with much higher electrical potential than the other. When the external circuit is complete, it discharges its "surplus" electrons through the electrolye to the other panel until both are at the same potential. At that point, the battery is dead flat. To recharge it, you then add an external source of power (the charger) to one of the plates to reverse the process and increase the difference in plate potential. So, at that point, you could quite easily reverse the positive and negative plates if you want.

A starter battery has thin plates with lots of surface area in contact with the electrolyte. This allows it to give relatively large current flow. A deep cycle has thicker plates for longer cycle life. However, that external charger has to get those electrons into that much thicker plate. As an analogy, the difference between wading in 50mm mud and 500mm - which is harder. So if an average golf cart battery is designed for extreme cycling, it will have very thick plates. So why would it not need more energy to charge?

The actual question is whether the effect is really noticeable in practical terms. I don't think so, but I have never charged a golf cart battery with solar. Unless you have and compared it directly with the alternatives, you won't know.

So in Neddy's focused example, one 12 volt battery will have similar characteristics to 2 x 6 volt of equivalent voltage and capacity. But if the common 2 x 12 volt parallel configuration is used, then the 6 volt in series solution for equivalent capacity has half the number of plates. This is one reason why in theory it is less likely to fail than 2 x 12 volt in parallel. But to get the same capacity, the plates must be.... I'll leave that to others to figure out. Of course it will make a difference to how they charge.

Just to add, I also think a bit of hyperbole is going on with the Bushtracker response. Professional wisdom dealing with many years of investigations has taught me you don't go in and rubbish something without absolute proof. Heck Neddy, I even listen to you some of the time :)

Dene

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Re: 6 volt batteries

Postby WoodyZ » Mon Oct 19, 2015 11:27 am

Dene
Here is original post again.
Naki585 wrote:Hi.

I have read that 2 x 6 volt batteries in series is not a good idea due to the extra thickness of the plates. This causes the solar to burn too much energy to "excite" the thicker plates. This is called "warming the plates"

Has anyone else heard of this theory, or is it just a load of rubbish.

We have 2 x 6 volt batteries giving us 260ah and 240w solar and we are very happy with setup.

Cheers.

The only possible comparison is with a single 12 volt battery.

The characteristics of two 12 volt batteries in parallel would be very similar to four 6 volt batteries linked with two 6 volts in series connected in parallel with the other two in series. Plenty of people use this configuration just the same as plenty use only one 12 volt battery.

Whether they are starter batteries or golf cart batteries is also irrelevant.
Cheers, Neil

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Re: 6 volt batteries

Postby Neddy » Mon Oct 19, 2015 11:43 am

Teardrop wrote:Actually, it (putting batteries in parallel) is what is under discussion here.
Dene, you seem determined to get this thread off-topic!
The question was on the wisdom or otherwise of putting 2 x 6 volt batteries in SERIES.

An Australian caravan maker said that this was not a good idea.
He was wrong - both in theory and in practice.

You are on a hiding to nothing here, Dene. Has it escaped your notice that most every poster responding to this query either HAS 2x 6 volt batteries in series and/or rubbishes the caravan maker's unconventional "advice"?

Where is the support for your opinion - or the caravan-maker's?

Neville.


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