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Old 10-26-2013, 09:55 AM   #1
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Default Moving and Adding Batteries To Rear Bumper

I have a 230DS which is a bit tongue heavy. It has a front bath and kitchen. I have two Trojan batteries and two 20 pound LP tanks sitting on the front.

I recently installed a 230W solar panel and would like to add more batteries. How would it work if I put eliminated the batteries from the tongue, and placed four on the rear (obviously building a box lengthwise for all four batteries and adding rear support). I would then just keep one LP tank on the front.

Would there be an issue with trailer weight balance shifting 280 pounds to the rear?

How would I find this out?

Thanks in advance.
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Old 10-26-2013, 09:57 AM   #2
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Not sure what happened to my post but many words are missing. My concern is balance and trailer sway.
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Old 10-26-2013, 10:32 AM   #3
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Default Weighing the tongue

Chris --

First, I did not see any missing words -- your post made perfect sense.

Second, are you sure that your rear bumper can support the weight of the batteries?? Some folks have reported metal fatigue at the point that the bumper attaches to the frame. But most of those folks have added bike racks, which exert a lot of leverage. A battery rack may be less stressful -- not sure.

Third, assuming that you want to go ahead with this, here is a way to mock up the rear battery rack and then test the tongue weight -- using metal C clamps, clamp a plywood platform to the rear bumper. The platform would have to be stout enough to support the batteries, temporarily. The C clamps would go over the forward frame member of the platform, holding it to the bumper.

Next, use a bathroom scale to weigh your tongue. Sounds crazy, but it is not. The trick is to create a lever arm, with a properly positioned fulcrum, so that you don't break the scale. You can easily google this technique -- it really works. It requires some simple math -- for that part, I enlisted my wife's help!

Good luck, and let us know how it goes.
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Old 10-26-2013, 10:45 AM   #4
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One other caution... Bear in mind that you are not only adding 280 to the rear, but, removing that weight from the front. That leaves a delta of 560 lbs... You mention that you are "tongue heavy". How heavy? Your trailer should carry 12-16% of its gross weight on the tongue and even 20% would be better than 6%. A towable, of any sort, should never be "balanced". The heavier the trailer, the more weight should be carried on the front end. Tractor trailer rigs carry, basically, all of the weight of their freight on the kingpin. My 5er, at ~11,000 lbs, is a 5er so that it can carry a bit over a ton on the king pin... Until you know your actual weights, tongue and GVW as towed, I would be leery of moving a lot of weight to the rear.

Also, I'll repeat the warning about that weight on the bumper. It won't hold it. You'll need to fab a stout steel platform that is welded and reinforced to the frame on each side. That's going to add additional weight to the whole project on the wrong end of your trailer.

Can be done, but, IMHO, you are going to have to add weight to the front to keep your tongue weight in the 12-16% of your gross towing weight for safety and stability purposes. There's a reason manufacturers put the heavy stuff on the tongue and not in the rear...



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Old 10-26-2013, 12:40 PM   #5
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Thanks guys for replying so fast. Yep, I do need to make some reinforcement changes to the rear if I am going to do it.

The other thing is to get to the scales and get it weighed. I saw the diagrams on the internet for using a bathroom scale. I might give it a try next week.

The spec sheet I found says the dry weight is 3883 and the tongue is 497. So add two 20 lb tanks filled, and two Trojans at 68 lbs a piece, it looks like it is getting heavy. The black, grey and fresh water tanks are also up front. It says on the specs sheet that LP and water are not included.

Also, wouldn't I want to keep the batteries together? Instead of being 4.5 feet from the converter they would be 16ft from the converter and I have heard distance can be an issue too.

Sorry I'm not a whiz at this so some of this may sound crazy.
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Old 10-26-2013, 02:45 PM   #6
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Even with two batteries and and two 20 lb tanks filled, your tongue weight isn't "heavy". Your dry weight and no liquid propane or batteries, your calculated tongue weight (based on your 497 lb figure) is only a tad over 12%...bare minimum. That was how it was built; to have the bare bones amount of tongue weight to get it to the dealer. Adding batteries and the liquid portion of the propane would only add maybe 200 lbs. That would bring your tongue weight up to 697 if that full weight was on the tongue as it hangs off your tow vehicle. It isn't though, not really. I'd have to get heavy into physics to prove it mathematically, but, trust me, some of that weight is also on the trailer's axles and not all of it is transferred to the tongue. Has to do with fulcrums; just like being able to use a bathroom scale to measure the actual tongue weight. Maybe, and that's a big maybe, 80% of that 200 lbs is on the tongue, meaning the actual downward force of the tongue would be 677 lbs. Add the full 200 lbs to the trailer's gross and you've got 4083. That 4083 isn't going to be right either, because you have to add all the "options" on your rig to that weight; microwave, television, awning, etc. Your true dry weight is apt to be closer to 4700 lbs., but, we'll stay with 4083 for this calculation. If your tongue weight is 677 lbs (and that is a heavy guess) and your new dry weight is 4083, you are still at only a tad over 16% tongue weight. That is perfect. Add all those "options" onto your trailer though and that percentage starts to plummet. If your weight is actually 4583, then your tongue weight is only a tad over 14%... If your actual towing weight is closer to 5000 lbs (loaded with the options and your camping gear) your tongue weight of 677 (again, a heavy guess) is only is only 13%; a tad low, but, still at the minimum mark.

That's why you can't just assume that you are "tongue heavy" without getting some weights to actually use in the computations. "Dry weights" are a fictitious number...good for a rough guess when going out shopping, but, actually meaningless when you start talking about tongue weights or if the trailer is too heavy to tow because no trailer is actually ever delivered at the "dry weight" as advertised. As a further example, my '08 210WDS, IIRC, had a dry weight listed at just a tad under 4000 lbs. My actual towing weight for our trips was a tad under 6000 lbs. loaded with my "options" and all of my equipment. I towed right under the max GVWR of the trailer. Dry weight? Lets call the listed for my 210WDS at 3900 lbs. My trailer weighed 4700 lbs. when I left the dealer's lot (I stopped and had it weighed on the way home)...and that was before I added my "stuff" to it; another 1200 lbs.

Get some real numbers before you worry too much. Your trailer was designed to be perfectly safe and towable with full propane tanks, dual batteries (even though most folks get by with one; the rack will hold two and that is taken into consideration) without being concerned about "excessive" tongue weights. You'll also find that unless you load lead into your pass through storage compartment that your tongue weight is engineered to be able to handle the normal load in that compartment and your full tanks and still be well within the engineered strength of your tongue and the best handling of that load. Remember when I mentioned the fact that even though all that weight is in front of the axles, only a portion of that weight is on the tongue...a large portion of that rests on the trailer's axles. Which is important...anything that is added behind the axles comes off the tongue at a much higher percentage rate because there is only the single fulcrum (the axles) to mitigate load transfer. That's why the trailers are designed so that most of the storage and tanks are between the tow vehicle and the axles and not behind them it spreads the load between the tongue and the axles; also the reason that toy haulers can be so easily skewed with regards to adequate tongue weight as their storage largest loading is behind the axles and is easily overloaded.

Sorry to get so "long" in explanation, but, weight calculations and "balancing" is much more complex than "I'll just plop the weight here and I'll be fine..."



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Old 10-26-2013, 03:21 PM   #7
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Thanks Webslave,

"I'll just plop the weight here and I'll be fine..." that's why I thought I should ask. I know that the design takes all those things into consideration and to mess with that might cause trouble.

My rv is in the Rio Grande Valley for the next month and I am going there every week for work. Hopefully when I finish I can run by the scales and also to the bathroom scale test on the tongue.
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Old 10-26-2013, 05:05 PM   #8
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Good show...get some numbers so that you'll know exactly what you are working with, that's the safest way to go.

Forgot to answer your electrical question though...if you go with the batteries mounted in the rear, make sure that your wire gauge is sufficient to handle the current. Longer runs = heavier wire, to allow for the inherent resistance of the wire. There are calculators on the web that can help you determine the proper gauge for the length of run.



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