# Dual Batteries



## jasonrebecca (Oct 30, 2007)

I am thinking of getting a second 12v for extended dry camping, which is what we prefer to do anyways.
But I have read about 2-6v as well.

What are the pros and cons of having one setup over the other?


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## GarethsDad (Apr 4, 2007)

I would say cost is the biggest con, weight would be second. 2-(6)volt batterys will give you the same power (reserve) than 4-(12) volt batterys and 6volt batterys are designed to be discharged further than a 12volt battery. 1 exide gc2 batterys have a 525 minutes at 25 amps rating where 1 marine/rv deep cycle battery has a 140 minute at 25 amp rating for a group 24. http://www.exide.com/pdf/exide_specs_april_2003.pdf. James


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## GoVols (Oct 7, 2005)

Oh boy, might as well ask which truck brand is better.









6V batts are built for heavy, deep discharge and thousands of cycles . . .

Larger 12V batts can give you nearly the same or equal amp hours . . .

Some will argue if one 6V goes bad, you are hosed; if one 12V goes bad, you are still OK with 12V power . . .

I went the 6V route since I had to replace my Group 24 12V anyway, and I liked the idea of being able to really drawn down and otherwise abuse the 6V set. They have more than proved themselves on extended dry camping trips.

If you have a good Group 27, 29 or 31 12V battery already and don't need to replace it, it would be cheaper to simply add another as a reserve.


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## Sayonara (Jul 23, 2007)

Great question here, i was thinking the exact same thing !! Whats up with these group numbers?


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## BoaterDan (Jul 1, 2005)

The group number is basically the physical size of the battery, which also generally equates to the capacity of it. A group 27 is bigger physically and has more capacity than a group 24.

The standard battery box on our trailers is for a group 24. It generally takes some modding to get a bigger box mounted.

It is mostly personal preference, but the real differences boil down to a few things:

2x6v will likely provide more capacity and life expectency for a given amount of money. IMO, this argument is somewhat overrated, as recent true deep cycle 12v batteries are closing that gap and people tend to make this point from the perspective of what was available 10 years ago - IN MY OPINION. But it's still the case that batteries like the Trojan 6v are tried and proven thousands of times over, and affordable.

2x12v provides two independently useful batteries. That argument is also probably overrated, IMO, as you're really buying a system in which the probability of one of the two batteries failing is pretty low. Keep in mind that you ideally want to have two identical batteries, so just adding a second one to what you have isn't an argument for not going the 2x6v route.


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## Sayonara (Jul 23, 2007)

BoaterDan said:


> Keep in mind that you ideally want to have two identical batteries, so just adding a second one to what you have isn't an argument for not going the 2x6v route.


are you saying adding a second battery to my existing 12v is not as efficient. Sound i be deciding between 2 new 12v or 2 new 6v?


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## PDX_Doug (Nov 16, 2004)

Sayonara said:


> Keep in mind that you ideally want to have two identical batteries, so just adding a second one to what you have isn't an argument for not going the 2x6v route.


are you saying adding a second battery to my existing 12v is not as efficient. Sound i be deciding between 2 new 12v or 2 new 6v?
[/quote]
DT,

I think the concern is that both batteries in the system are close to equal in performance. If you add a new - well performing - battery to a system with an older - lesser performing - battery, the old battery will draw down a lot of what the new battery has to give as the system tries to equalize itself. In any case, whether you go 6V or 12V, you need both batteries to be as equal as possible going in.

Happy Trails,
Doug


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## Oregon_Camper (Sep 13, 2004)

When we had our Coleman pop-up, I had 2x12v batteries and they did a "good" job.

When I bought Y-Guys Outback, he had 2x6v batteries installed and they last much longer then our 212v batteries did, and the Outback has a LOT more lights and I'm sure we are using more power.

Could it be the 2x12v's I had on Coleman were poor quality ---- sure

Am I a happy camper with the 2x6v's ----- You bet









Would I go back to 2x12v if I needed to replace them ---- No Way.

... but YMMV


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## Sayonara (Jul 23, 2007)

I see. i think ill go the 2 6v route.


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## Oregon_Camper (Sep 13, 2004)

Sayonara said:


> I see. i think ill go the 2 6v route.


how often do you dry camp?

How long do you dry camp (in days?)


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## Sayonara (Jul 23, 2007)

Oregon_Camper said:


> I see. i think ill go the 2 6v route.


how often do you dry camp? Couple times a year.
How long do you dry camp (in days?) 5 days each
[/quote]
I would really like to get a Honda 2000i next year as well. 
I could be talked in to the 2 12 volts batteries if it makes more sense. im really not sure, i need to look at the cost differences. if there are any. Im assuming it would be ranked like this.....
1. buy an additional 12v battery for the one I have (least expensive option)
2. buy 2 new 12v (more expensive)
3. buy 2 new 6v (most expensive)


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## Oregon_Camper (Sep 13, 2004)

Sayonara said:


> I see. i think ill go the 2 6v route.


how often do you dry camp? Couple times a year.
How long do you dry camp (in days?) 5 days each
[/quote]
I would really like to get a Honda 2000i next year as well. 
I could be talked in to the 2 12 volts batteries if it makes more sense. im really not sure, i need to look at the cost differences. if there are any. Im assuming it would be ranked like this.....
1. buy an additional 12v battery for the one I have (least expensive option)
2. buy 2 new 12v (more expensive)
3. buy 2 new 6v (most expensive)
[/quote]

Assuming these "dry camping days" are in mild weather, (so heater doesn't run often) then for only 5 days, I'm guessing you'd be fine with the 2x12v's. Once they both fail and you have to replace them, then you could go with 2x6v's.

Are these dry camping sites in an area with direct sunlight? I have a solar panel that I can plug into my systems with a quick connect and it seems to do a good job providing a bit more power to my 2x6v's.


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## Nathan (Jan 2, 2007)

Sayonara said:


> I see. i think ill go the 2 6v route.


how often do you dry camp? Couple times a year.
How long do you dry camp (in days?) 5 days each
[/quote]
I would really like to get a Honda 2000i next year as well. 
I could be talked in to the 2 12 volts batteries if it makes more sense. im really not sure, i need to look at the cost differences. if there are any. Im assuming it would be ranked like this.....
1. buy an additional 12v battery for the one I have (least expensive option)
2. buy 2 new 12v (more expensive)
3. buy 2 new 6v (most expensive)
[/quote]
Costco sells group 27 12V batts and 6V batts. I think the 6V is ~$10 more if I remember correctly. I think the 6V's ran about $70 each.


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## jasonrebecca (Oct 30, 2007)

Oregon_Camper said:


> Are these dry camping sites in an area with direct sunlight? I have a solar panel that I can plug into my systems with a quick connect and it seems to do a good job providing a bit more power to my 2x6v's.


What solar panel did you get? I am also interested in this. I am thinking that between the solar panel and dual batteries I will never have to worry about the lack of power.


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## PDX_Doug (Nov 16, 2004)

Sayonara said:


> I would really like to get a Honda 2000i next year as well.


And this brings up another angle to consider...

If you are going to be toting - and investing $$$ in - a generator, does the battery setup you use really matter that much?
The big value in the 6V systems is the number of days you can go before draining the batteries. Five instead of two (or whatever it is). But if you have a generator, what's wrong with two days capacity?

One might also make the argument that having spent a grand (or two) on a generator (or two), the more use you make of it (them), the better the return on investment. Sure there are other considerations that come with this argument, such as noise disturbance, convenience, etc., but it's something to consider.

Happy Trails,
Doug


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## Oregon_Camper (Sep 13, 2004)

jasonrebecca said:


> Are these dry camping sites in an area with direct sunlight? I have a solar panel that I can plug into my systems with a quick connect and it seems to do a good job providing a bit more power to my 2x6v's.


What solar panel did you get? I am also interested in this. I am thinking that between the solar panel and dual batteries I will never have to worry about the lack of power.
[/quote]

Here is a link to the one I have...

http://www.earthtechproducts.com/p192.html


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## Sayonara (Jul 23, 2007)

All very good points!!! Thanks!!


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## Oregon_Camper (Sep 13, 2004)

Sayonara said:


> All very good points!!! Thanks!!


Glad to help.....


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## kjdj (Sep 14, 2004)

PDXDoug nailed it.

Add a 12 volt battery your system is only as good as the worst battery (your existing battery).

The rule is when 2 batteries are charged together (paralleled or series) they should measure within 2/10ths of a volt of each other to get the best performance from the 2.

So if you have an old battery and add a new one you won't get the capacity that 2 new ones would have.
This is why everyone says 2-6 volt batteries are better than 2-12 volt. The 6volt conversion requires 2 new batteries. When you add a 12 volt battery your adding it to an existing "old" battery.

There is really no difference in capacity between the same size 2-12's or 2-6's if the batteries are new and matched within .2 volts at full charge.

A 6 volt battery has 3 high amperage cells and a 12 volt has 6 cells half the amperage of the 6 volts battery.

The 6 volt batteries tend to be heavier and physically more robust because of the thicker high amperage plates.


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## Sayonara (Jul 23, 2007)

interesting. mabye the ~$150 for a 2 new battery setup would be better saved and used for the generator.


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## Oregon_Camper (Sep 13, 2004)

Sayonara said:


> interesting. mabye the ~$150 for a 2 new battery setup would be better saved and used for the generator.


Batteries...Solar Panels...Generator --- It comes down to how and where you camp. Some like the power of 2xbatteries...some like using Solar...other have issues with Generator noise.

For me...I have all three and it depends on where I'm going, as to how I plan my power usage for the trip. My generator is used about 95% of the time to charge my 12v boat battery. I do plug the Outback in when it is running, but I don't really "need" to...it more of a "why not" thought process.

Dem's my thoughts....YMMV


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## BoaterDan (Jul 1, 2005)

One of the options I'm considering if I get into dry camping is just getting a $100 el cheapo generator for charging the batteries. A Honda 2000 won't run the air conditioning, and is way overkill for just charging the batteries.

As somebody mentioned, you probably don't even need a second battery at all if you go that route.

Remember this truth that helps me sometimes:
To the extent two options are equally attractive, it can't possibly matter which one you choose.

Some people are just more "comfortable" with 12v batteries, some people like that 6v are more tried and tested for true deep-cycle applications. Bottom line is they'll almost certainly both work perfectly fine.


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## Sayonara (Jul 23, 2007)

BoaterDan said:


> One of the options I'm considering if I get into dry camping is just getting a $100 el cheapo generator for charging the batteries. A Honda 2000 won't run the air conditioning, and is way overkill for just charging the batteries.
> 
> As somebody mentioned, you probably don't even need a second battery at all if you go that route.
> 
> ...


ill use the 2000 for more than just charging the batteries. We'll enjoy the 110v as well. if its hot enough for the AC, we will go to a CG with hookups I suppose, or use a fan.


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## BoaterDan (Jul 1, 2005)

Sayonara said:


> ill use the 2000 for more than just charging the batteries. We'll enjoy the 110v as well. if its hot enough for the AC, we will go to a CG with hookups I suppose, or use a fan.


All right, then I'll just go boondocking with you and I don't have to buy _anything_!


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## Sayonara (Jul 23, 2007)

Sounds good!! dont forget your glow-in-the-dark necklaces !!


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## raynardo (Jun 8, 2007)

I started with one 12-volt battery (Interstate). I was disappointed with the performance of that OEM battery, so I bought a second matching Interstate. Still disappointed - the things didn't last a whole day. After 10 months the first Interstate didn't hold a charge so I got a free replacement under their warranty terms. Still disappointed. After 16 months the first AND the second Interstate failed. Dealer said no more warranty, dude. So I told him to keep his pieces of junk.

I went out and purchased two Trojan 6-volt golf cart batteries. I love 'em!!!

The beginning of November I did two nights in the desert, and I never had to use the generator to recharge those batteries. I did however use a $100 15-watt solar photovoltaic panel to keep the batteries up to snuff. This three by one foot lightweight panel isn't mounted anywhere, I just rest it against the OB and point it at the sun.

Sadly, when I still had those 12-volt batteries and disconnected them, after a month in storage they were dead. These 6-volt batteries hold their charge much, much better.

Once you go the 6-volt route, you'll never look back.

For those folks that give you that song & dance about "what if one of them fails". Well, you can always carry a spare 12-volt battery or one of those 12-volt jump-start devices. I have both. I carry the spare 12-volt battery (gas mat) under the queen bed to power my CPAP device when I'm dry camping - it'll power it for three nights. I keep it charged with a trickle charger when I'm at a campground with shore power. Otherwise I charge it with a charger when I have the OB at home packing it up - usually the night or day before I plan to head out.

I've also found that when I have my OB connected to my truck's electrical trailer outlet (and the truck is running) the electrical system works fine. And I also travel with a Honda generator. So I ever have to worry about a dead battery.

Overkill? Maybe. Or maybe "never die!"


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## Sayonara (Jul 23, 2007)

OK, Dan....you and I need to hang out with Raynardo! he has EVERYTHING!!


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## PDX_Doug (Nov 16, 2004)

I'm thinking maybe I'll go with eight 1.5V's
They don't really have the longevity, but they are cheap and easy to replace, and a packet of 'D' cells hardly weighs anything at all!
Besides...

They keep going... and going... and...

Happy Trails,
Doug


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## Sayonara (Jul 23, 2007)

going...and going....


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## PDX_Doug (Nov 16, 2004)

and going...and going....


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## BoaterDan (Jul 1, 2005)

raynardo said:


> I started with one 12-volt battery (Interstate). I was disappointed with the performance of that OEM battery, so I bought a second matching Interstate. Still disappointed - the things didn't last a whole day. After 10 months the first Interstate didn't hold a charge so I got a free replacement under their warranty terms. Still disappointed. After 16 months the first AND the second Interstate failed. Dealer said no more warranty, dude. So I told him to keep his pieces of junk.


Well, this is a good example of what I meant about being careful how you analyze the anecdotal experiences of others.

Raynardo, I hade the exact same experience with the Interstate junk. What a waste!! I've since replaced them with two 12v deep cycle batteries from WalMart that have worked beautifully. I have no doubt that if I shelled out the money and bought a couple of AGM 12v batteries I'd be tickled pink for the next 10 years.

A bad experience with a particular 12v setup isn't really evidence that 12v is inferior.

However, this does point out something I've been saying all along, that you simply can't go wrong going with a proven 6v solutioin like the Trojans. BTW, you could still jump your truck kfrom a 6v setup if you were careful to hook up correctly, right?


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## Oregon_Camper (Sep 13, 2004)

BoaterDan said:


> ill use the 2000 for more than just charging the batteries. We'll enjoy the 110v as well. if its hot enough for the AC, we will go to a CG with hookups I suppose, or use a fan.


All right, then I'll just go boondocking with you and I don't have to buy _anything_!








[/quote]

Come on out to Oregon....I'll take you boondocking to places not on any maps!


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## Nathan (Jan 2, 2007)

BoaterDan said:


> However, this does point out something I've been saying all along, that you simply can't go wrong going with a proven 6v solutioin like the Trojans. BTW, you could still jump your truck kfrom a 6v setup if you were careful to hook up correctly, right?


For anyone who drains their truck battery while it is within reach of you trailer. Just plug in (if you're on a switched line, you might need to key on). The TV batt will have enough juice within an hour to start. A single 12V deep cell can transfer enough to get you on the road.... (Don't ask me how I know....)


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## Sayonara (Jul 23, 2007)

Thats good to know! 1 hour eh? id a never thought.


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## BoaterDan (Jul 1, 2005)

Nathan said:


> However, this does point out something I've been saying all along, that you simply can't go wrong going with a proven 6v solutioin like the Trojans. BTW, you could still jump your truck kfrom a 6v setup if you were careful to hook up correctly, right?


For anyone who drains their truck battery while it is within reach of you trailer. Just plug in (if you're on a switched line, you might need to key on). The TV batt will have enough juice within an hour to start. A single 12V deep cell can transfer enough to get you on the road.... (Don't ask me how I know....)








[/quote]

Now, that's a tip I hope to never need AGAIN.


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## Nathan (Jan 2, 2007)

Sayonara said:


> Thats good to know! 1 hour eh? id a never thought.


Ok, for people like Sayonara, I should specify that I did this with my pop up and minivan combo. That 3.8L engine probably put out the same torque as the starter motor on the 6.4L. A Diesel truck could take a little more time!!!


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## Sayonara (Jul 23, 2007)

Nathan said:


> Thats good to know! 1 hour eh? id a never thought.


Ok, for people like Sayonara, I should specify that I did this with my pop up and minivan combo. That 3.8L engine probably put out the same torque as the starter motor on the 6.4L. A Diesel truck could take a little more time!!!








[/quote]
thats what i thought. i might need to bring along one of those minivans in case i need the added starting power.


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## Oregon_Camper (Sep 13, 2004)

Sayonara said:


> thats what i thought. i might need to bring along one of those minivans in case i need the added starting power.


LOL....


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