FB - move batteries to rear of trailer

[Ohiobrits]

I'm currently considering a 2014 or 2015 25FB or 27FB and will need to lighten the tongue weight a little due to payload limitation with my TV and the potential to add a ProPride hitch at about 250lbs of additional tongue weight.

I understand the consequences of reducing tongue weight below 10% and won't be approaching that lower limit so I'm not looking for advice or cautionary notes on that topic.

I would however like some advice, photos etc on what is involved in relocating batteries to the rear of the TT in the storage under the dinette. I understand that I will need sealed batteries. I think the easiest method would be to run a positive wire from the battery box positive terminal/wire to the rear. I assume the Airstream is grounded to the frame like a vehicle? if so do I locate a ground point at the rear also or do I need to run a negative wire to the back to the battery box negative terminal/wire also?

As far as cable routing from front to back goes, I assume I rout this inside the cabin down the side via the bathroom then cross to the other side of the trailer using the raceway between the axles then along to the front? Any photo's or examples of anything similar, where to access the cabinets to complete the pull etc?

Are there any other easier options to complete the battery move and wiring ? I thought maybe running a protected conduit run under the bottom of the trailer and then up at the rear would be a way to go but would prefer the wiring inside to limit the potential for damage.

Thanks.

[68 Overlander]

What is your tow vehicle?

[slowmover]

Is there a weight change reduction with better batteries? That might do most of what you want.

[slowmover]

Originally Posted by 68 Overlander

What is your tow vehicle?

Read his other 1or 2 posts.

[idroba]

Although the negative side of the 12 volt system is bonded to the frame it is not the way the negative current is carried in an Airstream built since about 1970 or so. There is a dedicated wire which carries the negative side of the circuit (white in Airstreams). So, you will need to run two wires, one positive (red or black) and the other negative (white) to the new location.

[68 Overlander]

I agree.

[Rocinante]

If you're going for the gusto, you may find it attractive to swap out the two group 24 12-volt flooded batteries for a pair of 6 volt AGM batteries in series. They will be a little bigger and certainly heavier, but if you are putting them aft you might as well get more amp-hours in the bargain.

I'm assuming you'd run some heavy gauge wire to the batteries from the front battery box to your chosen storage location to reduce the chance of voltage loss. Someone here can probably guide your choice on that.

I'm actually considering the same thing, on a smaller scale, in my 27FB. When I get sick of my group 24 flooded batteries, I'm likely to replace them with a pair of 6V AGM batteries placed under the foot of the bed. That will move the batteries several feet aft of the battery box, though they'll still be forward of the axles. This move should reduce the weight impact on the tongue from the heavier batteries, I think, and may even result in an overall reduction on the tongue.

I'm sure we'll also stay well north of the requisite 10% weight on the tongue. I can always put more things in the front bedroom or the storage compartment under the bed if it comes up light.

[xrvr]

Think about eliminating one propane tank and getting a smaller other one. Or moving them to the rear. Or eliminate one battery also. One tank gone and one battery gone will really drop the weight. Everything us a compromise. Don't make unsafe mods in order to use a safer hitch, counterproductive. Don't know you tow vehicle, but can you carry propane or an extra battery in it! If it's not a truck, no.

[Msmoto]

Once we know your TV, better advice can be offered. Doing the modification on a new trailer, 2014, sounds rather expensive. And if not done with a great deal of care can be a disaster. And, I would imagine expensive, as the access for a huge cable (look at a 30 or 50 Amp power cord) would be difficult to find, unless routed underneath.

Is it possible to modify your TV, adding air springs, or something, to allow the tongue weight of a stock AS? If it cannot handle the tongue weight, can it actually tow the trailer?

[lewster]

Any cable run that will be almost the length of the trailer, plus bends and a cross-trailer path will approach 30'. That is a HUGE run for any battery system and would require (without doing the actual math and considering the size of the battery bank) a minimum of 2/0 and perhaps 4/0 cables. That would be 60 feet at $12/foot (4/0 class K welding cable)...........or $700 +/-.

A far better and easier alternative would be to purchase a pair of quality AGM batteries and place them under the bed, which will effectively lower the tongue weight significantly. I have many solar installations in the FB series and the Classic series trailers where the batteries have been relocated inside in this manner. No problems!

[Tincampers]

Have you ever done this in a RB configuration? Placing the batteries under the long side of the lounge seating? What about off gassing of the batteries? Would you need to vent these just in case they do off gas?

[xrvr]

AGM battery's don't gas. Jim

[Tincampers]

Originally Posted by zigzagguzzi

AGM battery's don't gas. Jim

Under normal conditions but will if severely overcharged.

[lewster]

Originally Posted by mrprez

Under normal conditions but will if severely overcharged.

While this is true, thermal runaway or severe overcharging (15.5 VDC @ 77ºF) is extremely rare. I have never seen this in several hundred Lifeline AGM battery installations which, BTW, are the ONLY batteries that I would place inside.

If the relatively minimal possibility of outgassing is your immediate concern, I would seriously consider the new generation of Lithium batteries, which do not gas under any conditions. AM Solar is in the final stages of preparing their own version of the new LiFeYPo-4 battery formula (with the addition of Yttrium) and they should be available by the end of Jan.

These batteries (while expensive) promise to be game changers in their electrical capacity, light weight and extreme longevity (10-15 years).

I will post an the characteristics, sizes and weights of these new batteries as soon as the details become available.

[Tincampers]

Those do sound promising...so, if I were to move the batteries inside, what happens to the wires that currently run to the battery box outside?

[KJRitchie]

Has anyone weighed their tongue with the batteries removed from the tongue battery box? Two grp 27 AGMs weigh 63lbs each (126lbs) in the front box. Since the battery box is not directly on the coupler what is the difference in weight?

Also with the same batteries moved to under the front bed next to the compartment where the store/use relay is located what is the difference in tongue weight?

If you only reduce the tongue weight 50lbs is it worth the effort and cost? One advantage is you could put large 6v AGMs under the bed and not have to worry about modifying the tongue battery box lid height.

What battery restraints are used for batteries located under the bed?

Can the existing cables be removed easily from the battery box?

I'd like to see a photo of an install under the front bed of a 25fb.

Kelvin

[lewster]

I'll look for one in my files. I custom built restraints for these installations.

With respect to the existing battery cables at the tongue box, these are either removed and replaced with slightly larger class K welding cables, usually 2AWG or simply pulled back thru their existing hole in the floor and re-routed to the new battery bank. Re-sealing of the floor penetration is required in either case.


Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
541-490-6357

[KJRitchie]

I have a Sherline scale. When I pull my AS out of storage in a few months I'll weigh my tongue weight again and remove the batteries and weigh. My Interstate grp 27 batteries are not quite as heavy as the AGMs of the same size. They are supposed to be 53lbs each. I'll also place them under the bed and weigh the tongue.

Kelvin

[boondockdad]

I'm surprised nobody has mentioned possible frame damage from the weight.

There's a boat load of threads discussing how a bike carrier on the rear of an A/S will cause all kinds of havoc... a couple of flooded group 27's placed in the rear would probably cause the trailer to spontaneously explode into a haze of aluminum confetti and floating pink batt

[lewster]

There's a huge difference between placing 150 lbs inside the confines of the frame/shell structure and cantilevering about 75-100 lbs FROM the rear of the frame and solely depending on it's integrity. The moment arm of a cantilevered load will greatly increase the actual weight seen by the frame while the load inside makes full use of the Airstream's monocoque frame/shell/floor structure.


Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
541-490-6357