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Old 08-04-2009, 09:46 AM   #1
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Two 12V vs. two six volt batteries

I have a 2003 LY (gas) 30' and coach batteries need replacing. Would I mess things up if I used two six volt golf cart batteries? Or should I stick with two deep cycle 12 Volt RV batteries. Also, has manyone mused the Energizer Brand SAM's Club sells? I don't do very much dry camping. Thanks.
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Old 08-04-2009, 10:12 AM   #2
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If you installed two six volt batteries, the first thing you would have to do is rewire the system because the two 12's are wired parrallel, and the two 6's would need to be wired series.

Then, if the two 12's are 50 amp hour batteries, to get the same capacity out of two 6's, they would have to be 100 amp hour batteries, and would probably be more expensive.
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Old 08-04-2009, 10:53 AM   #3
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Two 6 volt Golf Cart batteries will give you more available Amp Hours to run your stuff while boondocking...

10 inch 12 volt (group 24) has about 80 Amp hours x two batt's = 160 AH

12 inch 12 volt (group 27) has about 105 Amp hours x two batt's = 210 AH

(2) 10 inch long, 6 volt GC (group GC-2) have about 225 amp hours total when hooked in SERIES..

GC batteries are taller, so you'll need about 2 inches more space..

Wiring two 6 volt GC is no big deal, as you'll use one wire between the POS of one battery, and the NEG of the other which is SERIES wiring - to give you 12 volts you'll need...

You're two 12 volt batteries are wired in PARALLEL, which is POS to POS, and NEG to NEG on both batteries...

SERIES wiring will add the voltage of the batteries together, but the AH rating remains the same as one battery...

PARALLEL wiring will add the AMP HOUR ratings of the batteries together, but the VOLTAGE remains the same as one battery...

If you don't do much boondocking, and your existing type 12 volts have performed fine when you did, I really don't see much cause to change to the 6 volt GC batts...you probably won't see any more life in terms of 'years' of service with the GC's...

If you do intend to do more boondocking, then the GC's will allow you to run your 12 volt stuff a bit longer than the two 12 volts...

GC's are a great battery for RV use, but not all that important if you don't really need that extra capacity...as compared with the 12 volt deep cycle batteries, that is...
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Old 08-04-2009, 11:33 AM   #4
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Ah, the age old question: which battery is better? I've used both over the years and I have to say that Golf Cart batteries are superior to regular 12v, Size 27 batteries. They're beefier (each weighs 62 lbs), provide more amperage, and generally last longer than regular Size 27 batteries.

I used to use Trojan T105 Golf Cart batteries but they're $135 each. Saturday I bought two Golf Cart batteries from Costco for only $75 each. I'll give them a try but friends say they are just as good (and heavy) as the Trojan T105s.
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Old 08-04-2009, 11:43 AM   #5
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I don't want to muddle things up but there is a 3rd choice. A larger battery could be put in. I have a 4B AGM which gives 200 amp hours there is a bigger size I think it is 8B which I think is about 300 amp hours. The 4B was cheaper than buying 2 separate batteries although I did have to make room for it.
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Old 08-04-2009, 11:59 AM   #6
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I don't want to muddle things up but there is a 3rd choice. A larger battery could be put in. I have a 4B AGM which gives 200 amp hours there is a bigger size I think it is 8B which I think is about 300 amp hours. The 4B was cheaper than buying 2 separate batteries although I did have to make room for it.
How much are they and how much does each battery weigh? I've been told the AGM don't do well in the AZ heat. Don't know if that's true, but since I've been happy with the Golf Cart batteries, I'll continue to use them.
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Old 08-04-2009, 12:18 PM   #7
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They are called 8 D batteries used one for years great batteries just hard to handle because of size have went to the 4D battery easier to handle.have been happy with its performance.we have always called 8D could be wrong and they are 8B?
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Old 08-04-2009, 02:16 PM   #8
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Spat 61,

Since you said, "I don't do very much dry camping," there is no reason to increase your amp hour capacity, nor your draw down %. Go with the less expensive 12V batteries.
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Old 08-05-2009, 02:40 AM   #9
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Quote: "I've been told the AGM don't do well in the AZ Heat."

FYI, we replaced the two OEM batteries with Optima Blue Tops when the OEM batteries failed after only one year. The Optimas have worked well for the past three years. However, we installed a marine battery switch that allows the selection of Battery A only, Battery B only, A+B, and both off.

We only charge overnight, once a month; and the batteries are set to OFF the rest of the time, except when we are on the road. I think that not leaving the batteries to cook 24/7 has contributed to their longevity (so far).

Also, we only use one battery at a time, and save the other as a backup when we dry camp for several days. This works well if you overnight somewhere with hookups a couple of times a week, or if you are on the road every couple of days. And, so far, we haven't needed a generator.
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Old 08-25-2009, 01:39 AM   #10
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Something for everyone-

BCI Battery Group Size Chart

This is a list of the more common battery BCI sizes. These are DIMENSIONAL sizes ONLY and NOT capacity ratings.

Looking down low on the list you will see the 4-6-8D size batteries. The 8D is truly a bear of a battery and weighs in (depending on the amp hr rating) at 75-90 lbs.

As to WHICH battery is the "best" is like starting an argument about Fords and Chebys.

The key to the selection process is essentially like filling up at a gas station. With gas you are buying gallonage. With batteries you are buying electrons. The more of any item you buy, the more it will cost you.

There really is NO such thing as battery A being 'better' than batter B. At least not from a quality standpoint. Batteries are batteries. The REAL issue is CAPACITY. And here again there are many ways to measure. The STANDARD definition of battery capacity is the AMP/HR rating. There are other rating to be sure.

If you are buying a battery to crank your gas/diesel engine you would use the automotive standard of CA or CCA. CA stands for Cranking Amps and CCA stands for Cold Cranking Amps. The DIFFERENCE is the two ratings is significant. The CA rating is the amount of current (in amperage) that a battery will deliver at an ambient temperature of 32 degrees F and not have the terminal voltage drop below 9.7v The CCA rating is the amount of amperage that a battery will deliver at an ambient tempreture of 0 degree F and not have the terminal voltage drop below 9.7v.

Obviously, the CCA rating (IF BOTH ARE EQUAL IN NUMBER) is more desirable as it will provide MORE cranking power at a lower temperature. It is often the practice of the battery saleman to SUBSTITUTE a CA rating (higher in number) when the buyer specifically requests a CCA rating in order to compete on price. The SAME rules apply to batteries as to any other commodity-you get what you pay for, and if you are NOT careful, you will not get even that.

Automotive batteries are NOT suitable as "house batteries" as they are designed for EXTREME amperage draw in short bursts of time. House batteries are of a different design internally and are designed for slower discharge, longer discharge, and deeper discharge. An automotive battery subjected to a deep discharge (to 0 terminal voltage) will be irrevocalbly damaged and in many instances, distroyed, while a deep cycle battery will not be the worse for wear after many such discharges.

6v or 12 volts? What to do? Generally speaking a 6 volt battery (as many as you need to meet minimum demand) will work better that a 12 volt. This is so only because of the ability of the manufacturer to place MORE, and thicker, lead plates into the 6 volt battery case that they can in a 12v battery case OF THE SAME SIZE BCI class.

Newer battery technology has been hard at work recently putting old battery technology on the back burner. GEL batteries, waterless batteries (low/no maintenance) and closed system style batteries are all making a grab for the conventional flooded cell (the kind that has been on the market for some 80 years) type we are used to buying. The primary attempt at the new designs is to get away from the single problem of flooded cell technology, the water/electrolyte issue. With water as the starting eletrolyte of all flodded cell technology, it must be replenished as the battery goes through its normal cycle of discharge and charge. The charge cycle also is responsible for the production of free hydrogen in the cells. If the hydrogen disipates into the atmopsphere, all is well and good but there is still a chance that an overcharge or short will cause the hydrogen gas to ignite with often disastrous results. If you permit a batterys electrolyte to drop below the tops of the cell plates, damage and short life is the result. So, batteries must be maintained AND they are a safety hadzard.

To the rescue-the sealed battery. No water, no gas, NO problem. WRONG?
Even though the manufacture will tell you that the unit is sealed for life and needs no regular maintenence, it is JUST as possible for a new type battery to fail and for the SAME reasons. Overcharge and loss of electrolyte. Only NOW you can't as an owner, do anything about it except buy a new unit.

The GEL battery technology is essentially a hybrid of the no maintenance unit and and a totally SEALED unit. The electrolyte is actually a gel like material and is ROLLED up inside of a special lead grid like a jellyroll and stacked upright like a D cell battery into a plastic battery (BCI Class) case, 1 cell = 2v, 6 cells = 12Vs'. They had their problems early on as the gel would continue to separate under extreme loading and render the battery useless. The hotrod crowd likes them as they permit long term storage (but NOT long term life) without outgassing and causing battery corrosion and a cleaning problem. My opinion, if you have a classic car, get one. Motor home, NO.

The lastest technology is the AGM or Absorbtion Glass Mat battery. You can read about it here. AGM Absorption Glass Mat Batteries - DC Battery Specialists

These are expensive but COULD be the answer to the big question on the minds of consumers everywhere, Paper? or Plastic?

The Deuceman
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Old 08-25-2009, 09:35 AM   #11
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Two 6 volt Golf Cart batteries will give you more available Amp Hours to run your stuff while boondocking...

10 inch 12 volt (group 24) has about 80 Amp hours x two batt's = 160 AH

12 inch 12 volt (group 27) has about 105 Amp hours x two batt's = 210 AH

(2) 10 inch long, 6 volt GC (group GC-2) have about 225 amp hours total when hooked in SERIES..

GC batteries are taller, so you'll need about 2 inches more space..

Wiring two 6 volt GC is no big deal, as you'll use one wire between the POS of one battery, and the NEG of the other which is SERIES wiring - to give you 12 volts you'll need...

You're two 12 volt batteries are wired in PARALLEL, which is POS to POS, and NEG to NEG on both batteries...

SERIES wiring will add the voltage of the batteries together, but the AH rating remains the same as one battery...

PARALLEL wiring will add the AMP HOUR ratings of the batteries together, but the VOLTAGE remains the same as one battery...

If you don't do much boondocking, and your existing type 12 volts have performed fine when you did, I really don't see much cause to change to the 6 volt GC batts...you probably won't see any more life in terms of 'years' of service with the GC's...

If you do intend to do more boondocking, then the GC's will allow you to run your 12 volt stuff a bit longer than the two 12 volts...

GC's are a great battery for RV use, but not all that important if you don't really need that extra capacity...as compared with the 12 volt deep cycle batteries, that is...
I recharge our deep cycle with a Honda 2000 when boondocking. That usually will take an hour after an evenings use including DVD viewing. I like the idea of two 6 volts. What would the H-2000 charge time be?
Neil.
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Old 08-26-2009, 04:25 PM   #12
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Neil,

I assume you plug the trailer's shore power cable into the Honda genny, when you recharge your batteries...time to recharge your battery system then depends on the rating of your converter/charger, and of course, how far your battery is discharged...

I have a 3-stage charger in our AS, and it's rated at 45 Amps, and probably can 'pump out' about 35 amps in it's bulk charge rate, and so in ONE hour, replace about 35 amp/hours back into our battery bank...at about 80% of full charge, this charger will throttle back to about 'half' it's initial charging rate till the batteries are fully charged...

I guess what I'm trying to say is that it's difficult, at best, to predict the 'how long will it take?" question...the best way to check for a full charge is to take a hydrometer and dip a couple of battery cells to see how far along the recharge process is coming - but nobody wants to go to all that trouble in their RV...so, I, like many others, run the genny till I feel the 3-stage charger has gone into it's 'float mode' - or, as I try to do, check the actual voltage of the battery system, the day after charging (to allow the batteries time to stabilize) to see it the voltage is around 12.65 VDC...if not, I need more genny time....
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Old 08-26-2009, 07:23 PM   #13
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If you use 2 6V batteries and one goes bad you have NO 12V system.
If you use 2 12V batteries and on goes bad you still have one to power your 12V system.
I had to help some folks in the boondocks when one of their 6V died on them.
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Old 09-30-2009, 11:26 PM   #14
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Ah, the age old question: which battery is better? ....snip....
Ayeeee! I'm building a 3600w inverter system in the 26' LY that is completely stand-alone (until I plug in the shore power plug) from the engine bay and house battery system.

Since I have too much time on my hands while I wait for The Boss to retire at the end of October, I researched the "which is better" and which is "value/cost" efficient...and as many other variables as I could calculate.

Bottom Line #1: (for me), I am using two 170Ah sealed 12v, in parallel, which are made attaching a 10A three stage charger that will only be operable when shore power is "humming". They weigh 131 lbs each but are only 11 in tall, ~6" wide and ~ 20" long. Not good for a engine compartment. But there are only two of us and I think we all take too much stuff, anyway. So I was willing to give up the storage space. Right now, I have to wait for the solar. $$$$$

Northstar Battery Company

Bottom Line #2: There's no substitute for experience. I have none. So for anybody who says, "I tried this for (X) years", I respect and appreciate the info.

Bottom Line #2a: Find a battery distributor in your area. A place that does nothing but batteries. Make a friend. They are better to talk to than what you get back by staring at the battery rack at Costco. I've done it all.

Bottom Line #3: There's no right or wrong way...I mean in *choice*....Better wire it correctly. You could *definitely* be wrong on that one.

Bottom Line #4: Waaaaay too many choices for set-up combined with hundreds (or thousands) of different owner use patterns. If a person does not know how many Ah he or she needs, or does not know peak watt surge or continuous watts needed, he or she will soon find out if the system was built "too thin". You'll probably never know if you've overbuilt.

For me, it's onward to test the new batteries and our actual Ah use in real life...Then it's off to concoct the solar charging...(and, also, maybe to figure out how to get a charge from the alt while driving). Then it's off to install an auto-switch to connect the separate system I'm building to existing stock MH set-up. I think unplugging the shore power cord from my new set-up every boondock morning may get old. We'll see. But, right now, it's set up that way to keep everything separate under the "Do No Harm" clause.
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