Visit our Popular Forums

Inland RV Center, In · 03-07-2010, 09:12 AM

Quote:

Originally Posted by ROBERT CROSS

Yes...but don't you need two 6v to make one 12v?

it would suck for you to be me.

Batteries are made up of a series of 2 volt cells.

A 6 volt battery has 3 and a 12 volt has 6 cells. There is nothing that can be done to alter that.

However, when you put batteries or lights as an example, in series, when one fails, they all fail, just like the old Christmas tree lights.

As an example, take 2 100 amp 6 volt batteries, 600 watts each and put them in series. You will have 12 volts at 100 amps, or 1200 watts.

Then take 2, 50 amp 12 volt batteries and put them in parallel. You will now have 12 volts at 100 amps, or 1200 watts.

The big draw back with the two 6 volt batteries in series is when one quits, your done. When batteries are in parallel, when one quits, you remove it, and you still have a source of power.

"IF" 2 six volt batteries was a better deal than two 12 volt batteries, Airstream would have switched to that many years ago.

The odds of power failure with 2 six volt batteries in series, is "TWICE" that of 12 volt batteries in parallel.

Twelve volt batteries are easily found, not so any more with 6 volt batteries.

Go to Costco, and see how many of each they have on display.

Lastly, more than likely a battery will fail when on a trip. With the 6 volts, your done, no matter what you do. Now your trip has a problem, because you will have to search for 2 batteries.

With the 12 volts, remove the bad one, and replace it when you get around to it, perhaps not until you get back home.

The only test equipment needed for the 12 volt battery setup, is a cheap volt meter.

Andy

heslinhotel · 03-07-2010, 09:15 AM

I purchase my batteries from an Interstate wholesale supply house locally. I usually get "blems" that have a scare on outter case, but batteries are new with warranty. Cost on the 2 12v were $30 each, 6v were $40 each. Beats the retail prices and allows you to repalce as necessary without breaking the bank.

Ag&Au · 03-07-2010, 09:25 AM

Quote:

Originally Posted by overlander63

Pretty much. But if you only have one 12 volt battery, and a cell croaks, it also sucks to be you...

Why would you only have one 12 volt?
If you have room for two 6 volts. you've got room for two 12 volts.

heslinhotel · 03-07-2010, 09:29 AM

On my current 31, it had only a single battery. The external box hatch was intact but inner plastic box was missing. I bought 2 covers with plastic boxes from a wrecked 06 Classic. Had to modify the box to hatch connection due to angle of cover, but now have an enclosed battery box to contain battery gases from entering the cabin. The support wire on cover was too short to allow the hatch to open a full 90 degrees. this made fitting type 78 deep cycle from fitting. I had to lengthen it. The support wire was not really necessary because hatch will be stopped by frame a little over 90 degrees anyway. I am still contemplating wether I am going to put in the additional 2 pack of 6v batteries on this one.

Ag&Au · 03-07-2010, 09:34 AM

Quote:

Originally Posted by ROBERT CROSS

Do your batts have handles?

This is not the brand or style battery I use...(best picture though). I struggled with the same problem til I fastened a pull strap attached to the end of the battery where the handle is attached.
Lift up and slide out, it still ain't easy with a heavy AGM but it is doable..

...

Good idea. I am going to look into that. I use a strap horizontally around the battery, but your method looks like it would work better. I also have a thin piece of slick plastic to help the battery get up over the lip of the compartment.

Regards,
Ken

Ag&Au · 03-07-2010, 09:50 AM

First of all, let me establish my credentials - I am not a battery expert and make no claim to be.

The only reliable way, that I am aware of, to test a battery's condition (not just whether it is charged or not) is to fully charge it and hook it up to a known value load. Then plot the voltage over time as it discharges. Compare that to the specifications. I have a device that does that. It connects to a laptop computer and plots a chart of the battery's performance. I have only used it a few times. What I learned is, that by the time I think it is worth doing, I pretty much know the battery needs to be replaced anyway.

Regards,
Ken

ROBERT CROSS · 03-07-2010, 09:51 AM

Quote:

Originally Posted by w7ts

Good idea. I am going to look into that. I use a strap horizontally around the battery, but your method looks like it would work better. I also have a thin piece of slick plastic to help the battery get up over the lip of the compartment.

Regards,
Ken

Yeah...that little 1/4" lip is a real PITA...

...I'll find that piece of plastic and give it a try, that with the lift strap==piece of cake.

Thanks....Bob

kentuvman · 03-07-2010, 01:38 PM

Is the "Point" of a battery blade to disconnect it when connected to A/C?

ROBERT CROSS · 03-07-2010, 05:48 PM

Not really...just a quick way to isolate the batteries when stored for long periods.

Helps prevent deadness...

I just disconnect neg cables...

DreamStreamr · 03-10-2010, 06:12 AM

Quote:

Originally Posted by Inland RV Center, In

The big draw back with the two 6 volt batteries in series is when one quits, your done. When batteries are in parallel, when one quits, you remove it, and you still have a source of power.

"IF" 2 six volt batteries was a better deal than two 12 volt batteries, Airstream would have switched to that many years ago.

The odds of power failure with 2 six volt batteries in series, is "TWICE" that of 12 volt batteries in parallel.

Twelve volt batteries are easily found, not so any more with 6 volt batteries.

Go to Costco, and see how many of each they have on display.

Lastly, more than likely a battery will fail when on a trip. With the 6 volts, your done, no matter what you do. Now your trip has a problem, because you will have to search for 2 batteries.

With the 12 volts, remove the bad one, and replace it when you get around to it, perhaps not until you get back home.

The only test equipment needed for the 12 volt battery setup, is a cheap volt meter.

Andy

I'm not saying Airstream Co should do 6v batteries on new units. But I will stand up for 6v being the better choice for most everyone who can fit them in.

A pair of 6v batteries provide us an awesome improvement in available amp hours and resiliency -- we can draw them way down and they just come back to full strength just fine. First cost was little higher than a pair of 12v, weight is almost fifty percent higher than 12v, and size (for our 6v 225a/h batteries) is a little taller than 12v.

With all due respect, Airstream Co does what's a better deal for Airstream Co. Airstream Co works to a lowest common denominator for its market. They are obliged to, in a big way, to stay in business. We find examples of this scrimping in a lot of things, including the foam mattress, foam in cushions, bimetallic thermostat, single step in lieu of double step (on CCD 22 and many others).

Two 12v batteries are cheaper than two 6v and yes, 12v are available most everywhere. We might not find 6v in Tehachapi or Needles, Ca, or many other places. But we'll always have alternatives, if one of the 6v batteries happens to fail.

My family's 6v cars, a "few" decades ago, were 6v elec systems and used single 6v battery. Maintenance was higher than on nowadays 12v no/low maintenance batteries. But, failure was rare. We're not driving around waiting for 6v batteries to fail on our trailer, either. If it does we can deal with it easily.

If we lose a 6v battery we can go to any local store for a pair of 12 batteries, just like anyone else. It's not like the choice of 6v batteries commits us to some irrevocable path. Just pull the 6v batteries, slip in the 12v ones, and change the jumpers so we're in parallel instead of series.

Whether someone loses a 12v or a 6v battery from a pair, should they not seriously consider replacing the pair and not just the failed one? We've read many places, the new battery and the "good" used one will not work together seamlessly.

Regardless, in the unlikely event we lose one 6v battery or the pair of 6v batteries, we can be back in business as quickly as any RV with 12v batteries.

Just one man's opinion,

Jim

hshovic · 03-10-2010, 07:28 AM

Yes, voltage is only one parameter, but I use it with temperature and battery documentation to estimate remaining charge. See http://www.airforums.com/forums/f449...age-46718.html

Also, I installed two 6V batteries two years ago. See http://www.airforums.com/forums/f449...tml#post514373.

They have held up fine, and produce enough juice for the job. Last fall I had them load tested (careful of hernia when removing them) and they were up to speed. For another performance check, see http://www.airforums.com/forums/f37/performance-report-battery-upgrade-one-year-ago-47574.html

Inland RV Center, In · 03-10-2010, 02:17 PM

Jim

Parallel batteries are the same as light bulbs.

When a bulb fails in your home, you know ehich one it is. If they were in series, you would have to test every bulb to find the bad one.

That was the same for Christmas tree lights, years ago.

Contrary to opinion, if a 12 volt battery that's a part of a pair fails, it can easily be identified, and removed from the circuit, and life continues on. No need to stop what your doing, and go chase down another one.

With 6 volt batteries, when one fails, your out of business, period.

The myth of 6 volt batteries being better, is total hog wash.

The auto industry changed because 12 volt operation, costs less money to create.

The wire is smaller, and the alternator is half the size.

There is plenty of talk today, with all the 12 volt gadgets that have been added to cars, to change to 24 volts. That again, will reduce manufacturing costs.

When that day comes about, I don't think too many owners will want to put 12 volt batteries in series.

The six volt setup does not offer one single advantage over 12 volts, but does offer many disadvantages.

But, to each his own choices and inconveniences.

Andy

DreamStreamr · 03-10-2010, 08:30 PM

Quote:

Originally Posted by Inland RV Center, In

The myth of 6 volt batteries being better, is total hog wash.

The six volt setup does not offer one single advantage over 12 volts, but does offer many disadvantages.

But, to each his own choices and inconveniences.
Andy

Andy,
I don't have your breadth of knowledge and wealth of experience. I'm merely a young traveler who worked on cars and machines over the past 42 years. I know my work experience doesn't apply to trailers and doesn't compare with yours.

I've experienced failures on three 12v batteries on two Airstreams in the past five years, had a great time with a hugely expensive 8D AGM on one trailer, and have had two years on this pair of golf cart batteries.

I can happily report zero inconveniences with these two 6v batteries. Monthly I look at the water level, and have added at least a quart of water in the past year. I check and, as needed, tighten the terminals. These batteries produce gaseous discharge (and they're in an outdoor and vented battery box).

Let's see, I must be missing something . . . Nope, that's it. Well, they do weigh more.

Oh yeah, that's the other inconvenience, they weigh more. And you already know what that means -- they're plates are much heavier. But wait, that's a good thing, isn't it? Yeah, they're rated 225 amp/hours for a pair compared to the 12v grp 24's 170 amp/hours per pair.

And they're made for deeper discharge with full recovery. For the very same reason this works on golf carts, where the batteries are capable of running to under 11 volts and still recovering fully, it works for RVs.

Wire size is irrelevant in this argument because the primary line voltage is the same for our system whether from series-paired 6v batteries or a pair of paralleled 12v batteries. We're not running primary wire to the trailer on 6v, it's still a 12v primary run.

Maybe our experience is not the norm, I cannot say. I'll leave that discussion to others. This is our experience based upon one pair of 225 amp/hr 6v golf cart batteries on a well-utilized 25' Airstream trailer.

All this, Andy, is neither myth, nor hogwash. It is all completely true.

HiHoAgRV · 03-10-2010, 09:10 PM

Quote:

Originally Posted by Inland RV Center, In

...Batteries are made up of a series of 2 volt cells...A 6 volt battery has 3 and a 12 volt has 6 cells. There is nothing that can be done to alter that...The odds of power failure with 2 six volt batteries in series, is "TWICE" that of 12 volt batteries in parallel.
...
Andy

I beg to differ but your logic escapes me on the 2x chance of failure for 6V systems. Actually a double 12V system has 2x the number of cells so logic suggests it has 2x the chance of failure...plus a failed 12V will usually cause the charger to boil the remaining GOOD battery...

Quote:

Originally Posted by Inland RV Center, In

...."IF" 2 six volt batteries was a better deal than two 12 volt batteries, Airstream would have switched to that many years ago....

Andy

Once again, this is probably not a technical decision but an inventory driven decision since they would have to increase the battery holder size (height) for the 6v dual option PLUS stock 6v batteries for the rare time when an enlightened customer ordered double capacity.

Xbob2 · 03-10-2010, 09:29 PM

Quote:

Originally Posted by HiHoAgRV

I beg to differ but your logic escapes me on the 2x chance of failure for 6V systems. Actually a double 12V system has 2x the number of cells so logic suggests it has 2x the chance of failure...plus a failed 12V will usually cause the charger to boil the remaining GOOD battery...

Once again, this is probably not a technical decision but an inventory driven decision since they would have to increase the battery holder size (height) for the 6v dual option PLUS stock 6v batteries for the rare time when an enlightened customer ordered double capacity.

Excuse me ... but if you loose 1 12 volt battery your system is reduced ... if you loose 1 6 volt battery your system is kaput! Everything else is academic ...

overlander63 · 03-10-2010, 09:34 PM

Quote:

Originally Posted by Xbob2

Excuse me ... but if you loose 1 12 volt battery your system is reduced ... if you loose 1 6 volt battery your system is kaput! Everything else is academic ...

True, but the way of the world says you will figure out you have a bad 12 volt battery after the second one is also roasted.

Xbob2 · 03-10-2010, 09:42 PM

Quote:

Originally Posted by overlander63

True, but the way of the world says you will figure out you have a bad 12 volt battery after the second one is also roasted.

You are way more experienced than me and I bow to your expertise ... but how does your statement invalidate my statement? Just askin' ...

HiHoAgRV · 03-10-2010, 09:44 PM

Quote:

Originally Posted by Xbob2

Excuse me ... Everything else is academic ...

I guess this is where academia and experience diverge

...my point was I've never lost 1 of the 12V batteries in a 2 battery system. I have lost several sets of 12 volt batteries when 1 failed and the charging system jumps into the 'i dunno know what to do' mode and fried the other.

Just one guys experience...

Having said that...
I'm stuck with multiple 12V's since the 6's are too tall for my boxes. But I do fully expect for a full system failure when 1 battery decides to 'exit stage left'...I've never had the advantage of a reduced capacity mode failure

Xbob2 · 03-10-2010, 09:46 PM

Quote:

Originally Posted by HiHoAgRV

I guess this is where academia and experience diverge

...my point was I've never lost 1 of the 12V batteries in a 2 battery system. I have lost several sets of 12 volt batteries when 1 failed and the charging system jumps into the 'i dunno know what to do' mode and fried the other.

Just one guys experience...

So ... the point is? 6 volt is better, 12 volt is better ... please explain.
Are you trying to say that no matter what the system all batteries go down at the same time?

HiHoAgRV · 03-10-2010, 09:58 PM

Quote:

Originally Posted by Xbob2

So ... the point is? 6 volt is better, 12 volt is better ... please explain.

Ahhh, the root question...
My experiece suggests that the proper answer is 'the dual 12V is not better...' so don't let that be your decision maker

I have used both styles and when something has gone bad, my entire system has failed. Choosing a dual 12v so 1 of the 2 will let ya limp by hasn't worked for me.

There is nothing like the morning smell of sulfur around the battery box

$$$$$