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Old 05-10-2010, 11:16 AM   #15
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I thing the gist of all of this is: 12 volts = 12 volts. I don't remember anyone trying to point out that two 6 volts somehow provided a different voltage. The potential is ALWAYS the same. I don't recall any argument about there being a difference in voltage or that contributing to more battery. We're simply talking about deliverable juice.... amp hours. There can be no argument that the new batteries are better than the old for doing that.
We're also talking about a group 24 "deep cycle" battery vs a true (golf cart) deep cycle battery. One is designed to be drawn down deeper, while providing more amps. This means more amp hours. The bigger plates in the 6 volt batteries are designed from the ground up to provide more juice than the 12 volts.
Yes, there IS a trade-off in weight. Why is it, do you think, that golf cart batteries are 6 volt instead of 12? Anyone? I served 6 years in the US Navy's submarine service. When you want truly deep cycle-ability, you go to smaller voltage ratings per cell. This gives you deep cycle and flexibility. The ideal situation, whether you're in a mountain cabin, completely off the grid, a golf cart on the back nine, a submarine operating in "enemy" waters (without a diesel or reactor for power) or in a 30-some foot Coors can by a stream in Montana is to be able to drop a cell (or group of cells) from your battery and continue to operate. Translation: Having both series and parallel hook-ups in your "battery" by having more than two six volts or having two six volts and a 12 volt or something like that gives you that kind of flexibility.
Now let's consider what is realistic. For many, the A/S is not a full-time home. If it were mine, I'd have 4 of those 6 volt batteries in it, with an appropriate charge controller/inverter and at least a couple photovoltaic panels. Do you "need" the power to run a microwave and a big screen TV from just your battery? Or is it just convenience? If you are draining your group 24s down below 35 - 50% on a regular basis, then you need to make adjustments. The golf cart 6 volts are a great step. Reducing consumption is also a great step, and maybe the most important one.
Tearing someone down or hinting they've bought into some snake oil scheme for being able to make what most would have to consider an improvement is not productive. Getting information out is.
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Old 05-10-2010, 12:28 PM   #16
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Quote:
Originally Posted by hhendrix View Post
...It seems there is often someone laying in wait to attack or demean meaningful attempts to provide information and experiences here.
yeah and there is OFTEN some1 claiming this crap has happened...

when it hasn't.

info/experience IS valuable here and so are EXPLANATIONS of why/how the info OR experience applies.

and that's all i read so far (except for a bit of ranting from the ranters)

Quote:
Originally Posted by Ellie & Carl View Post
I thing the gist of all of this is: 12 volts = 12 volts...
entirely true, but the notion promoted in many for 6v vs 12v threads is that there really IS some magic in the swap.

when in reality it's extra WEIGHT = extra juice.

ruggedness is largely not a factor for tongue mounted batteries (or inside/upfront)

ruggedness might be a minor issue for REAR mounted batteries but that's largely on old trailer issue.


Quote:
Originally Posted by Ellie & Carl View Post
...Tearing someone down or hinting they've bought into some snake oil scheme for being able to make what most would have to consider an improvement is not productive...
NO ONE is tearing down the o.p., it's all just an exchange of info, with suggestions to UNDERSTAND the relevant factors...

(weight, size, cost, amp hours, agm/flooded and so on)

but the assertion that "most" consider the change an improvement is categorically UNproven opinion, not fact.

with 1 battery we're committed to 12v and adding a 2nd is easy.

with 2 batteries i consider 2x6v as NOT an improvement and with the potential for NO juice.

with 4 batteries 6v vs 12v is largely a zero sum gain but with POSITIVES for either set up (or a combined set up)

with 6 batteries 6v may be a MUCH better approach, IF one has the space/weigh capacity and NEEDs that much juice.

1 can also buy/use one GIANT 12v agm (like the 250LB offering from lifeline) and that's another ok approach.

it's all about carrying the weight and having the space.
__________

i'd rather have MORE lp gas gadgets and carry lp gas, because there is a LOT more bang for every pound of fuel vs electricity.


Quote:
Originally Posted by Ellie & Carl View Post
... Getting information out is.
which IS the entire reason for the replies viewed as opposing the "amazing" results...

the op (new and their 1st post) use of the title term 'amazing' is part of the reason for ANY reply.

otherwise it's just a "i spent money, added weight and got more juice and i'm happy!" report...

happy reports are great stuff, especially with pictures.

but OFTEN these are product/vendor generated threads, designed to CONFUSE and ENCOURAGE the unsuspecting reader...

2 spend money...

CLEARLY that may not be THIS OP's intent, but it is very very common here.
____________

besides there are LOTS of of these threads with REALLY good info and maybe even MORE HEATED exchanges...

http://www.airforums.com/forums/f449...olt-14234.html

http://www.airforums.com/forums/f449...2-a-31854.html

http://www.airforums.com/forums/f449...lel-36595.html

http://www.airforums.com/forums/f449...ies-35364.html

http://www.airforums.com/forums/f449...ind-40614.html

http://www.airforums.com/forums/f449...ery-60141.html

http://www.airforums.com/forums/f449...ies-20633.html

http://www.airforums.com/forums/f449...ies-32463.html

http://www.airforums.com/forums/f449...ies-57392.html
_________

OFTEN the confusion is about some magik PEUK' effect in 6s vs 12s, and THAT is source of much heat and debate...

especially clear/useful info in posts 3 and 7 here...

http://www.airforums.com/forums/f449...ies-52395.html

http://www.airforums.com/forums/f449...ion-40065.html

http://www.airforums.com/forums/f448...nce-37921.html
________

so chill folks.

this 6 vs 12 thing is like solar/genset, axles or tires or corrosion or polish/clearcoat or MANY other common themes here...

folks LIKE what they like, and vendors SNEAK in sales crap a lotta wayz.

folks OFTEN don't wanna understand the basics and hope for magic from some new approach...

and often that magic is spread by members that WANT yer money...

other folks like to CLARIFY the important details and issues...

the goal being to PROMOTE clarity where hype is often a lot more exciting and interesting.
________

this thread is totally cupcake...

so far

((although i'd wager the REAL sellin' is happening via PM now...))

cheers
2air'
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Old 05-10-2010, 12:55 PM   #17
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to summarize the op and point out the questionable parts....

Quote:
Originally Posted by Aolani View Post

So far, amazing difference!

....we found a substantial drain on the batteries even over one evening while boondocking.

After MUCH research online and calling vendors, we settled on the Lifeline GPL-6CT batteries, wiring them up in series.

The results are amazing, compared to our previous batteries.

Before, our factory batteries were typically down to mid-40% in the mornings after very slight furnace use, lights, etc. This was after a confirmed full charge during the day. Now we wake up to a mid-90% charge level with the two new batteries - nothing else had changed that would account for that dramatic change in reserve capacity...
there is a learning curve to energy management and that is undoubtedly part of the amazing turn around.

1 night with furnace cycling in moderate temps shouldn't take them down to 40% on 2x12v unless...

it's really cold (batteries are cold)

or the reading is from a SURFACE voltage sensor ((the 40% will AMAZINGLY rise to 60-70% after an hour or so of NO use and some warming...)

what is a "confirmed full charge" ?

batteries truely at 40% will take up to 2 days of charging to be at 100% on shore power (with the oem p-lax c/c)...

and 8-12 hour or MORE of generator charging to be at 100%.

while only 2-3 hours may get them UPTO 80-85%...

and that 80-85% will SHOW at 100% charge/voltage on the typical gauge right after charging...

but turn on a light or WAIT 2 hours (with no use) and the gauge will show a more realistic equalized charge/voltage of 80-85 %...

this is a common point of confusion on the sunexplorer OEM wall meter and MOST wall meters reading surface charge/voltage.
____________

the GREATER reserve capacity is simply a result of starting with MORE JUICE (bigger heavier cells) , temperature variations

and the learning curve of power management.

cheers
2air'
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Old 05-10-2010, 04:12 PM   #18
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For years I used two 6v golf cart batteries and was quite happy with them until.... two months ago when one failed. No 12v power the last day of my camping trip really sucked.

Bottom line: 6v batteries have more amperage and can handle more deep discharges than your standard 12v battery, so I do think they are better batteries, but only if you have room for four or more. If you have room for only two, I'd go with two 12v, size 27s.

Just my 2 cents...
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Old 05-10-2010, 09:41 PM   #19
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Good points on the possible fallibility of a two 6 volts tied for 12 volts system. I totally agree. In fact, I agree with most of 2airishuman's .... (ahem) ... comments. What I don't agree with is the second post in reply to a new poster saying "No wonder so many get hornswoggled into spending a whole lot of money on things they may not really need". This is not getting info out. This is a nay-sayer trying to belittle someone who was trying to think outside the box (or tin can, in this case).
Another point: I do NOT have forward mounted batteries... I don't have tongue mounted batteries. Mine was originally a single 12 volt mounted under the bathroom sink. I've moved them forward, some. It is my intention to keep a 12 volt battery on board and to use a dual charging switch (marine) so that in the unlikely event I drop a cell or a whole 6 volt battery, I can still function. There are solutions and constructive ideas to solve any of the perceived shortfalls in what the OP did.
Oh! One more thing... in response to 2airishuman's comment "but the assertion that "most" consider the change an improvement is categorically UNproven opinion, not fact", I'd have to refer you to the HUGE off-the-grid community and the factual data derived from their long-term experimentation. I was not claiming that most A/S owners on the forum agree with this. I was relating information from documentation that has been building outside of the aluminum tube community for over 40 years. True deep cycle batteries cost more and weigh more and take up more space but can produce more amp hours, be drawn down further and recover more quickly than any of the 12 volt batteries out there. If I had the room, I'd have nickel metal hydride cells! But that's even more rediculous than a couple of golf cart batts.

As to the philisophical aspects of this discussion (as compared to the technical) I suggest reading Robert M. Pirsig's 1974 tome Zen and the Art of Motorcycle Maintenance. A great read!
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Old 05-10-2010, 10:05 PM   #20
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ok time for a group hug...

series or parallel?

((but don't suggest fixin my fancy bmw handle bars with a beer can shim))

cheers
2air'
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Old 05-10-2010, 10:05 PM   #21
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Quote:
Originally Posted by Ellie & Carl View Post
Another point: I do NOT have forward mounted batteries... I don't have tongue mounted batteries. Mine was originally a single 12 volt mounted under the bathroom sink. I've moved them forward, some. It is my intention to keep a 12 volt battery on board and to use a dual charging switch (marine) so that in the unlikely event I drop a cell or a whole 6 volt battery, I can still function. There are solutions and constructive ideas to solve any of the perceived shortfalls in what the OP did.
I think with your trailer battery configuration, it may be more practical to mount a group 31 battery behind the LP tanks on the A frame, and tie it into the 12 volt system there. That could be your single 12 volt battery, and it would have a great deal more amp hours contained within than a single group 24 or 27 battery. It would also counter somewhat the weight of the two golf cart batteries you are installing rearward (if i understand your post correctly).
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Old 05-10-2010, 10:59 PM   #22
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Wow - being new to AirForums and posting the results of an experiment is interesting, to say the least. Especially on a topic that apparently touches into the near-religious zone: 6V vs 12V batteries. Who would have thought - but it kind of reminds me of a similar debate within the sea kayaking groups when discussing rudders vs. skegs (and I'm a skeg person to be open about the issue). And apparently now I'm a 6V and a skeg guy...

On the serious side, this forum continues to provide me great insight, ideas and answers to my new-Airstream challenges - thanks to all of you for helping. It's a GREAT resource. It's also sometimes a fascinating read.

I won't try to address the various perspectives brought up after my initial and second post. But I forgot to mention some things that might help others who are struggling to get the most battery capacity for non-genset boon docking - after of course, the other mods (LED, solar, etc).

Most of what I'll add came from online resources, but I also had the opportunity to have some technical discussions with three battery manufacturers and the Airstream factory. All were excellent. By the way, the Airstream support guy mentioned they use Lifeline batteries exclusively (12V) on their factory solar installations - I won't go into the reasons in fear of this forum (smile) - you can call Airstream yourself.

Some additional observations / background:
* I'm actually a Electrical Engineer in my non-Airstream life (MIT 1980 - an old guy). So the concepts of watts, current and voltage are well known to me - I spent many years hunkered over a lab bench designing analog (and digital) circuitry in my career in the high-tech sector. Even did some power supply design many, many years ago.

* That said, I am NOT an battery expert. But I do know enough about battery discharge theory to accurately be able to state that "watts are NOT watts". The VA relationship is ok at a high, simplistic level, but in actuality the discharge characteristics of a battery are not linear, nor are they identical between battery "A" and battery "B". We all know this intuitively, as we realize a battery of capacity "X" AHr will perform differently under different loads, temperature, not to mention age.

* There is an interesting relationship called the Peukert curve that describes the efficiently of a battery. In essence, the Peukert number reflects the internal resistance of the battery and is a factor of battery design and manufacturing. This, I believe, is one reason why two batteries with the came "capacity" can have substantially different discharge curves == performance. Charging also, btw. Lower internal resistance allows the [better] batteries to charge faster as well.

* So far, nothing I've said yet is different for battery "A" which could be a 12V battery, or battery "B" which might be 6V. Nominal charge and Peukert characteristics apply to both. I won't go far onto the thin ice on 6V vs. 12V I've just been speculating why a battery from vendor "A" might perform differently from a battery from vendor "B" with the same AHr rating. Basically the design and manufacture of the battery.

* At the simplistic level, (2) 6V RV/golf cart batteries commercially available seem to have a higher AHr rating than a combination of (2) 12V batteries. Makes sense, since they're heavier, as is obvious from the specs. But I think it's more than that - the submariner guy here had an interesting and thought-provoking post. I think he's onto something and I'll stay away from that discussion. I think the answer is some combination of what has been said, plus the relative quality of higher end batteries, which I suspect have a different Peukert curve than cheaper ones - they don't spec those curves, much to the dismay of analytics like me!

Ok. Enough. While I may only have (3) posts, I think I have more words than (10) posts - smile. Maybe I have a Peukert curve or something?

Thanks again for all the insight and experience on this forum! It continues to be incredibly helpful!
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Old 05-10-2010, 11:10 PM   #23
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Welcome to the forums.
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Old 05-10-2010, 11:16 PM   #24
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Welcome to the forums.
Yeah, what he said!

Skeg and all.
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Old 05-11-2010, 03:01 AM   #25
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Originally Posted by overlander63 View Post
I think with your trailer battery configuration, it may be more practical to mount a group 31 battery behind the LP tanks on the A frame, and tie it into the 12 volt system there. That could be your single 12 volt battery, and it would have a great deal more amp hours contained within than a single group 24 or 27 battery. It would also counter somewhat the weight of the two golf cart batteries you are installing rearward (if i understand your post correctly).
An excellent idea! My LP tanks are only a few inches from the front of the trailer... but I like the prospects! Care to elaborate on your idea?
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Old 05-11-2010, 06:42 AM   #26
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An excellent idea! My LP tanks are only a few inches from the front of the trailer... but I like the prospects! Care to elaborate on your idea?
Yes. A pair of angle iron channels running across the A frame the width of the battery, with the positive and negative terminals connected through the umbilical to the tow vehicle would hold the battery to the A frame, and connect it electrically. I remember your '69 having a manual tongue jack, with a horizontal crank. You could either go with an electric jack or a manual jack with a vertical crank to gain some inches, and move the LP tank mount slightly forward. This will give you room for the group 31 battery. There are two types of group 31, you would want the one with the threaded posts.

Now, I work on these things every day, so what may be a hour or two project for me may be an all day project for many people. "Measure twice, cut once".
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Old 05-11-2010, 09:37 AM   #27
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I've posted lots of info about this 6 vs 12 subject here on Airforums, most of which has been noted above...

But, one additional comment would seem appropriate:

For those considering adding one additional 12 battery in parallel to the existing battery bank - make sure it is of the same GROUP size - mixing battery group sizes will result in different individual cell sizes, causing the batteries to charge and discharge at different levels - usually the larger cell battery never gets fully charged...

The age of the batteries should also be taken in account, as cell capacity is diminished with age - if you install a new battery with the same group, but the existing batteries are say, three years old, you will have different cell capacities due to age - if adding a third battery, I'd say only if your existing batteries are less than a year old - otherwise replace all three at the same time..

Ray
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Old 05-11-2010, 10:01 AM   #28
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re: "6v batteries have more amperage and can handle more deep discharges than your standard 12v battery," -- this is the pernicious myth that gets promoted ad nauseum without any substantiation or measure to support it. Again, I recommend to anyone looking at batteries who wants to make good decisions to look at things that can be measured and are supported by the manufacturer or retailer.

The fact is that deep discharges severely reduce any lead acid battery's life expectancy. The graphs for this are readily available for inspection at various battery websites. There is no "true deep cycle" lead acid battery of any sort and your RV is not a golf cart. All batteries are designed with the primary trade-offs being between cost, capacity, and 'ruggedness' and the differences as far as RV use are really rather minor when examined objectively. (look at the NAWS FAQ for the most commonly referenced battery life description. You'll note that there is no difference between 6v or 12v).

As noted, if you want more available energy capacity, get a bigger battery, which you can do with either 6v or 12v (or even 2v or 8v). The thing to keep in mind, though, is that even increases by a factor of two won't generally make much of an impact. This is because of the inherent variabilities in capacity over time and conditions and the limitations in what you can take with you.

As for Peukert, this one is subtle. If you look at the common measure of battery capacity, the 20 hour rate, you'll find that it is at about a 60 watt power draw. That applies to either the 6v or the 12v batteries of the typical 60# RV size. This is related to why they use a time based rate for the measure and provides a referent for Peukert calculations that normalizes voltage. Peukert considerations really aren't an issue until you start to talk about inverters with average draws exceeding several hundred watts.

Interesting that VA comes up. This isn't an issue in DC circuits, and, as such, represents an unnecessary complication IMHO. I see very many errors in these discussions with folks using AH and not considering volts which is why I recommend using watt hours for energy considerations. Proper units are a good way to avoid mistakes but you don't need to get too picky.

While it is good advice to keep all batteries in a bank as similar as possible, there is no need to get overly picky here, IMHO. We all run the trailer 12v in parallel with the tow vehicle 12v while traveling. If you do the calculations, you'll see they tend to only accept or give in proportion to their capacity.
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