Relocate batteries to rear bumper

[AB_SP295BHS]

Hi,

Am new to the forums, the site is a great resource.

I'm doing my second RV Solar project on a newly acquired SP295BHS and I'm considering putting the batteries (4 golf cart) on the back bumper. The benefits in my mind are:

• Get some weight off the front, so as I use the front storage that I stay in a reasonable tongue weight range, Durango's tongue weight limit is 720 lbs which isn't a problem if managed well.
• Allows me to run the solar on the rear portion of the RV and avoid a long run to the battery bank
• The fridge vent seems to be a popular way to get the power down from the roof and this, again, pushes one to the back end of the RV for the batteries
• While using a rear storage compartment for the batteries is possible if sealed and vented possible I don't want to loose the space, and hydrogen in a worst case scenario under a kid's bed is a terrible scenario. The weight would be all on the one back corner which isn't great.

Several issues come up:

• Collision, has anybody heard any rules against batteries on the back bumper? Common sense implications are welcome as well.
• Weight, at 70 lbs or so far a golf cart battery I'll be adding 280 lbs plus the weight of a box on the rear bumper...thoughts?
• Need to figure out how to get the 12V lead from the front bumper pulled back and into the rear of the unit.

My expectation is that having 280 lbs on the rear bumper will afford the addition of ~140 lbs on the front to stay within the factory delivered 550-600lbs. This will allow for a reasonable amount of weight to be added ~110 lbs for loaded propane tanks plus a few smaller items. Anything thereafter will need to be balanced with 2/3 going behind the axles and 1/3 in front.

The factory ratio of tongue weight is only ~10% on the hitch, at the scale it was 705 lbs with a single 12v battery and some propane in the tanks, this was 12%.

[Flybob]

That is too much weight to put on the rear bumper.

[mikakuja]

Don't do it..... The problem with putting that much weight on the back and removing weight from the front is that you end up with trailer sway problems. There is a few good videos out there that show the adverse affects produced when weight is not distributed properly in a trailer...

[AB_SP295BHS]

Originally Posted by Flybob

That is too much weight to put on the rear bumper.

It may be, but how do we explain this? I don't have a built in extendable rear platform like some RV's do, and I presume they are reinforced. Or, maybe not.

[DreiHunde]

Originally Posted by Flybob

That is too much weight to put on the rear bumper.

X2
You would have to reinforce/rebuild the entire bumper and mounts. Not saying it can't be done but if done correctly you would add a lot of weight back there.

and then there is the collision factor you brought up.....Being in the front the batteries are fairly protected from minor accidents. If you move them to the back you would need to build some protection for them and that would also add weight.....just a thought.

But whatever you decide keep us informed.....we love mods!

[B and B]

just try this. Take your propane tanks off. Put 6 cinder or cement blocks in the back of the trailer. Fill the water tank too. Go for a ride and watch the back end of the trailer sway all over the place. That should make you mind up pretty quick.

[SidecarFlip]

Originally Posted by B and B

just try this. Take your propane tanks off. Put 6 cinder or cement blocks in the back of the trailer. Fill the water tank too. Go for a ride and watch the back end of the trailer sway all over the place. That should make you mind up pretty quick.

Maybe add... Do it on a lightly travelled road so as not to cause an accident...

[GreenImp]

I believe that this idea COULD be done very responsibly even when considering the shortcomings of the typical TT back "bumper", and the weight balance issues.

When adding weight to the rear, and then also the front (because "now you can"), pay close attention to the total CCC of your trailer (and TV).

I envision the batteries lined end to end across the back of the trailer, in order to keep the weight ABOVE the bumper, as opposed to hanging out beyond it. This would reduce or possibly eliminate the need for reinforcement. Century Plastics makes nice battery boxes that could be used like this (2 batteries per box) Century Plastics: White Heavy Duty Battery Box - (part#: GCE-G)

Blue Sea Systems makes a very nice terminal mounted battery fuse that could be utilized to increase safety in the event of a rear end collision. https://www.bluesea.com/products/519...k_-_30_to_300A

[SidecarFlip]

Not withstanding, I believe there might be a safety issue with batteries mounted on a back bumper. In a rear end crash, battery acid spewing all over could be a big issue.

It is after all a bumper, not a battery carrier.

[AB_SP295BHS]

Originally Posted by GreenImp

I believe that this idea COULD be done very responsibly even when considering the shortcomings of the typical TT back "bumper", and the weight balance issues.

When adding weight to the rear, and then also the front (because "now you can"), pay close attention to the total CCC of your trailer (and TV).

I envision the batteries lined end to end across the back of the trailer, in order to keep the weight ABOVE the bumper, as opposed to hanging out beyond it. This would reduce or possibly eliminate the need for reinforcement. Century Plastics makes nice battery boxes that could be used like this (2 batteries per box) Century Plastics: White Heavy Duty Battery Box - (part#: GCE-G)

Blue Sea Systems makes a very nice terminal mounted battery fuse that could be utilized to increase safety in the event of a rear end collision. https://www.bluesea.com/products/519...k_-_30_to_300A

Indeed, I planned on building a battery box something like this:
https://www.etrailer.com/Accessories...FQ6raQod9fYF_g Yes, it would be additional weight as well.

To me this is about weight distribution, which is what most of the posts are concerned about. But, I'm not sure they make sense. The wheels are roughly 1/3 of the length from the rear of the RV, thus having 280 lbs on the rear (+box) would require ~140 in the front storage to compensate. Probably 160 lbs if you account for the removal of the single twelve volt battery.

The alternative is that I put the batteries out front and pack everything else into the bunk room...I'd have to put 560 lbs back there to counteract the batteries....

Good call on the fuse to aid in the event of collision.

[AB_SP295BHS]

Originally Posted by mikakuja

Don't do it..... The problem with putting that much weight on the back and removing weight from the front is that you end up with trailer sway problems. There is a few good videos out there that show the adverse affects produced when weight is not distributed properly in a trailer...

Understood, one objective is to retain the usefulness of the front storage compartment. If I put the batteries out front, which I can't on tongue weight, I'd have absolutely no ability to use the storage compartment.

Thus, about half the weight of the batteries placed in the storage compartment (~140 lbs) would retain the same balance as from the factory. I expect I'll end up with more weight in there than that.

But, I do accept that the placement of weight out back will add to sway...looking for an alternative...over the wheels is obviously ideal...but it's pretty busy around there and interior/unventilated.

[rsdata]

I think there may be some, including me that might think that because all of that weight is concentrated at the ends of the frame might cause a problem, certainly sway, but maybe torque on the frame. Adding weight to the trailer in a more linear fashion, distributed equally along the entire length of the trailer I think would be better.

Maybe two batteries up front and two in the rear? Connected with a #10 or 8 gauge wire should suffice for equalizing currents, and that would give you 12 V connections both front and back.

[bikendan]

Plus the rear end will bounce way more than the Aframe, when towing.

[SailorSam20500]

I did a search on your trailer. Saw a 2014 unit for sale from a Florida Auction site that was equipped with a drop down tray over the back bumper that looks to be attached directly to the frame. That might be a viable support mechanism. Bolting to the bumper, maybe not - how strong is the square tube bumper tube and how well is it welded onto the frame? Lots of reports of bumpers falling off trailers when people bolt extra stuff to them (look at some of the threads about adding a bike rack).

You are doing the right engineering work - looking at what weight you are putting where. Replacing weight of the batteries with other stuff is reasonable. According to common knowledge, lower tongue weight, near or below 10% of total trailer weight raises risk of sway. Related question - what are you using for a hitch? How good is the anti-sway on it?

Additional to your checking weight balance, what is the total weight of the trailer at project completion? Are you still safely under the axle and tire weight ratings of the trailer and the trailer GVW? Are you still safely under your GCVW? Will you be balanced left/right - don't overload one side of the trailer.

Running the wiring is just something to work out, make sure you are using appropriate gauge wire, possibly one size larger to reduce loss. You might just run some conduit under the trailer to protect the wiring. I note the FR just ran the wires for my brakes across the axle with a few wire ties - totally exposed. Apparently this is common practice!

You might check with some of your state motor vehicle people about legal issues of putting the batteries back there. Personally, it is probably a relatively low risk. If you get hit, it may splash some battery acid, but they won't explode. I have seen Jeeps with jerrycans for gas on the back of the vehicle which I would argue has a high fire risk.

[Trawlerphil]

Don't know about your rig, but Forest River says don't put anything on the bumper--too flimsy.

[itat]

AB_SP295BHS, correct me if I'm wrong on these numbers that I found doing an internet search ...

Your Durango has a 5.7L engine, a wheelbase of 120 inches, a payload capacity of about 1340 pounds and a max. towing capacity of about 7400 pounds.

Your Surveyor SP295BHS is 33' long with a "dry weight" of around 6000 pounds.

[Delco Bobby]

Originally Posted by Trawlerphil

Don't know about your rig, but Forest River says don't put anything on the bumper--too flimsy.

I recall reading a few posts where people complained about poor construction of trailers when their bumpers fell off or bent. The complainers all added weight to those bumpers, disregarding manufacturers warnings.

[Oaklevel]

Originally Posted by itat

AB_SP295BHS, correct me if I'm wrong on these numbers that I found doing an internet search ...

Your Durango has a 5.7L engine, a wheelbase of 120 inches, a payload capacity of about 1340 pounds and a max. towing capacity of about 7400 pounds.

Your Surveyor SP295BHS is 33' long with a "dry weight" of around 6000 pounds.

If this is the case the trailer / vehicle combination is at or over max capacity before adding more batteries. Take it to the scales loaded for camping and weigh it.

Either way I would leave the batteries at the front for the safety of your family and others.

[dbledan]

Cannot speak to the bumper being able to support the weight but there are several Volvo and BMW SUVs that have batteries in the back. They are behind a bumper and not on it but in the back. There are also lots of hybrid cars with batteries in the trunk. I don't think there is a legal issue...maybe safety if there is nothing between them and air.

[HONDAMAN174]

But the difference with those vehicles with standard batteries and hybrid is that they are CRASH TESTED to provide safety to all involved.

I think that the rear sway you might pick up would make it the scariest decision ever. I had a professional weld in a hitch and proper supports then went and put 150 pounds on it. TW was 450 before I did that. Got on the freeway and almost lost it immediately. Don't know how kept it together. And I was alone for that trip. Do you want your family in the truck now?