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Old 11-30-2007, 02:50 PM   #1
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Adding two batteries to the tongue to increase boondocking capacity

Greetings,
In my Saf SE FB 2007 I would like to double my boondocking capacity. Right
now in shoulder season it is one night. I want two. My OEM Interstate batteries were tested and are ok.

I have gone round and round with:

* replacing with higher capacity AGM (only a 10-20% increase)
* another solar panel (I have 120 w now, but little sun)
* going with 6 V (only a 20% increase)
* generator (noise)
* Batteries in the truck box (connections?)
* Why camp in the cold anyway? (That's from the wife).


My Airstream dealer suggested I just put another battery case on top of
the one on the tongue, and add two more batteries. Airstream says it
won't disturb balance or tongue weight (I have plenty of capacity on the truck).

Seems simple...

This seems like a reasonable solution, given it fits behind the propane.

I thought it should be removable to allow access to the lower batteries.

I understand you should always have the same make and general age of
batteries. (I have two new Interstate 24's now).

I can have my RV place fabricate it, and will probably make it somewhat
taller to accomodate later AGM and other kinds of batteries. I also might
insulate them to keep temperatures up, as well as vent them. There might
be issues with leakage, so I would need to place drainage holes carefully.

What does the membership think? As always I appreciate all feedback, opinions, and suggestions .
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Old 11-30-2007, 03:11 PM   #2
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A simple, quiet eu2000i Honda generator will solve your boondocking questions, battery recharging and make you a hero when your wife hears she'll be able to use the microwave back in the boonies (with the genset running that is).
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Old 11-30-2007, 03:29 PM   #3
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Hank,

If you look at the Lifeline web site under RV batteries and go to the comparison chart for battery capacities, you will find some interesting information.

They list their group 24 AGM battery at 80 amp/hours capacity and 149 minutes of discharge at the 25 amp rate. Two of these in parallel will give you 160 amp/hours and 298 minutes of discharge. Your wet cell Interstates are probably similar in their specifications, even though they won't hold a candle to any AGM.

Now look at th GPL-4CT 6 volt golf cart battery. It has a 220 amp/hour rating but a whopping 492 minutes of discharge time at the 25 amp rate. These numbers stay the same when 2 are connected in series to give you 12 VDC.

Basically, you are geting 194 minutes, or over 3 hours of extra capacity with a pair of 6VDC golf cart batteries over Lifeline group 24s and probably even more over your Interstates. The GPL-4CT will fit in your existing battery box if you raise the lid 1-1/2". I did this on my 19CCD.

The other benefits of AGMs are far longer service life (warranteed for 5 years and usually far exceed that) charge much quicker due to their much lower internal resistance when compared to wet cells or gel cells, and the ability to draw them down much deeper without any battery damage.

BTW, I am a dealer/installer for AM Solar and we use Lifelines exclusively in our new solar system installs. You will find that they work far better in your solar system than any wet cell.
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Old 11-30-2007, 06:27 PM   #4
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Hi Lew, will the golf cart batts fit in my compartments?

Would I have to change the wiring configuration to the charger-parallel/series?

Hope all is well,
Bill
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Old 11-30-2007, 07:14 PM   #5
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Quote:
Originally Posted by hshovic
What does the membership think?....
hi hank

given you've considered all of the other issues, and accounted for the power reserve differences...

i think the idea of adding 2 more identical batteries in parallel is a reasonable/cost effective approach.

as you've posted, switching to agms at a later time is still an option and will provide more juice (also they can be taken lower) with the solar set up.

sure a gen set is nice (i use one 2) but richL is full timing with solar and 4 12v (agms) batteries and doesn't carry one.

by only adding 2 more in parallel you aren't swapping out to the 6v mantra but always could some day.

take some photos of the box/arrangement the dealer fabricates and show us the results.

cheers
2air'
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Old 11-30-2007, 07:46 PM   #6
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You can increase the cycle life of ANY battery by warming it up. I've suggested this on many threads but no one pays any attention. Use gell-cell or AGM batteries, put them inside the trailer where it's warm and you'll get lots more use out of them. But then, what do I know. Only that it has worked for me since 1988. Darol
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Old 11-30-2007, 10:26 PM   #7
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I think you might have one problem stacking another battery box behind the propane tanks, that being how are you going to hinge the lid and get enough room to remove or install the batteries. The trailer shell on my Safari angles out towards the tanks as it goes up. I raised the height of my box to accomodate AGM's and had to trim the rear of the lid to clear the shell. Also, I don't understand how you can add 120-150 lbs there and NOT affect your tongue weight dramatically. It sure did on mine.
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Old 11-30-2007, 10:37 PM   #8
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Your battery capacity is best correlated with weight. Dsimiss the myths about the "true deep cycle 6v golf cart" fantasy. Even Trojan refers to their T105 as an RV/Marine battery and as a deep cycle depending upon the market target.

If you want more battery that means more weight which usually means bigger batteries. There are some trade-offs between capacity, longevity, and cost in a battery line (e.g. T105 vs T145 or SCS200 vs SCS220) but that usually isn't as much to worry about as are other factors.

When you add batteries in parallel, you will gain a 15% to 25% (2nd up to 4th battery) capacity benefit over simple addition because of the reduced current draw from each battery. (e.g. if one battery lasts 10 hours for you, two of them in parallel will last 22 hours or so)

Wiring and connections can also create significant losses.

When you put the batteries out on the tongue, you can loose 10% available capacity if they are 30 degrees colder. (right on Darol, but do keep in mind that code requires vented compartments even for AGM's)

Even from one cycle to the next, lead acid batteries can change in available capacity by 10% - 20%

A full charge will take 10 hours or more, which means that on-site recharging is usually only to 90% or so at best. Solar often suffers because the charge rate is not very vigorous and that results in premature aging via sulfation as well as more care to keep the charge up fully.

Keep in mind that continuous loads are harder on battery capacity than intermittant ones. That is one reason why watching a movie or two with a few lights on can be such a big hit on battery life. How you use the battery can make a big difference in what you can expect from it.

So if you are looking at differences less than 20%, forget about it. Your precision is exceeding the accuracy of what you are trying to measure.

At about 22 watt hours per pound or a kilowatt hour per typical group 27 type battery, you are looking at 100 lb or more to make a difference and that can be rather heavy on the tongue.

Trailers aren't really suitable for high energy boondocking - get a class A if you need that. The big class A guys talk about 8d's and L6's and a forklift to move them. They may also have 10 kw gensets with auto starting on low battery detection and such things.

Do keep in mind that you should keep each discharge cycle to a 15% to 50% state of charge level for best battery life. Be sure to recharge promptly, properly, and vigorously, too, as batteries don't do well sitting around at other than a full charge. Most batteries die from mismanagement and abuse.
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Old 12-01-2007, 07:09 AM   #9
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...The Answer is Blowing in the Wind....

The answer my friend is blowing in the wind... The answer is blowing in the wind...

One of my 100 or so "unfinished projects" involves adding a marine style 12v wind generator for boon-docking. I am sure there are threads in here somewhere for this, but my suggestion is to consider a small wind generator in addition to your solar. Wind generators are very popular on sailboats etc.

I am just sort of guessing that there aren't a lot of sailboats in Bozeman, Montana but I bet you do have wind... If I go down to the harbor here in Annapolis MD 50% or more of the boats all have wind generators on them.

You get a huge return compared to solar, and in tandem they make a great solution. Again, I have not yet done this, but I have seen it on many boats (a solar/wind combo).

Advantages are if you already have solar you already have all the circuitry and controller that you need (as long as you are within the rated watt capacity). Plus, wind gives you 24-hr production compared to 8 hrs or so for solar so you roughly get 3 watts to 1 watt for same rated units (ie, you would need a 300 watt solar panel to equal the weekly output of a 100 watt wind generator).

They are nice and fairly small, with the 42 inch diameter blades being very common. A very popular marine unit is the D-400 which costs around $1,000 and gives outputs as follows:

wind speed ~ 10 mph = output 40 watts

wind speed ~ 20 mph = output 190 watts

wind speed ~ 30 mph = output 400 watts (max wind speed rating)

My "plan" (also referred to as a "hair-brained" plan if wife is commenting) is to mount an 8 foot hinged pole on the jack pipe so that the wind generator can swing down and be secured over the battery box (bungied or something) while on the road and then when stopped swing the hinged pole back up so the bottom of the 42" rotor is 8 feet or more above the ground (don't want to give anyone a haircut).

Anyway, it would be right at the front of the trailer which is what you want to keep voltage drop low between the generator and the batteries.

Couple of photos attached.

regards Dave.
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Old 12-01-2007, 08:13 AM   #10
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I hear windmills can be rather noisy but they are an attractive option. For the 'build it yourself' type, the chispito might be worth looking at. Please keep us posted on your experience with it, Dave
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Old 12-01-2007, 11:09 AM   #11
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Try a Sun extender AGM battery and put it under the sofa. I use one that is 310 AH weights 165 pounds and got rid of the old lead acid batteries. Service life of the battery is about 10 years if you don't abuse them. So far ours is four years old and I and very pleased with it's operation over long periods of time boondocking. With a solar panel you should be able to BD for a long time.
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Old 12-31-2007, 11:20 AM   #12
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Where can one get a good deal on AGM's?

Having read numerous threads on the forum about batteries, I am leaning towards pair of AGM batteries. Anyone have any reccomendations as to where I can get good prices on the Lifeline batteries? (So. California)

Also, I noticed that Trojan has an AGM line now which I think is new... anyone have any experience with these yet?

-Torii
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Old 12-31-2007, 11:36 AM   #13
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Quote:
Originally Posted by T Man
Having read numerous threads on the forum about batteries, I am leaning towards pair of AGM batteries. Anyone have any reccomendations as to where I can get good prices on the Lifeline batteries? (So. California)

Also, I noticed that Trojan has an AGM line now which I think is new... anyone have any experience with these yet?

-Torii
Torii,

There is a wholesale battery supplier in South Santa Ana, on Warner I think, look them up in the phone book.

Bill
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Old 12-31-2007, 11:59 AM   #14
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Thanks Bill. I'll check that out.
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