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Old 10-16-2012, 01:04 PM   #15
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But hydrogen is lighter than air and will not vent down properly so floor venting is not going to work right.
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Old 10-16-2012, 01:09 PM   #16
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But hydrogen is lighter than air and will not vent down properly so floor venting is not going to work right.
I wonder if anyone told Airstream that? If I'm not mistaken Wayne's installation was by Airstream.

That raises other questions then. Maybe the solution is to have an upper and lower vent to allow for better breathing.
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Old 10-16-2012, 01:19 PM   #17
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All vintage AS trailers I have had used a vent tube which sloped upwards from the battery cap vent tube system located inside, as delivered from the factory, or they used a sealed from the inside battery box directly vented to the outside. My 310 motorhome had it's batteries in one of the exterior compartments, on the curved side, under the rig, and outside the living compartment. The box shown in the photos is one I have never seen, so can't comment on how it works.
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Old 10-16-2012, 01:28 PM   #18
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So what it boils down to is I need to make sure I have a vent that travels upwards to vent the hydrogen gases.

Do you recall what diameter the vent pipe is?
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Old 10-16-2012, 01:48 PM   #19
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Yes, the vent must be higher then the battery.
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Old 10-16-2012, 02:02 PM   #20
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Ok, I think my plan will be as follows:

1) build or buy a sealed battery box that will fit the area next to the genset compartment
2) if one battery it will be 12v (duh!), if two batteries I'll use 6v
3) vent the box from the top or top edge into the genset compartment
4) live happily ever after

Thanks all!

Brad
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Old 10-16-2012, 02:04 PM   #21
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Remember that the original batteries in wayneskid's Interstate were AGMs. Airstream may have chosen those because it was challenging to seal/vent the battery box well enough for cheaper flooded-cell batteries.
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Old 10-16-2012, 02:12 PM   #22
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Originally Posted by bkahler View Post
Ok, I think my plan will be as follows:

1) build or buy a sealed battery box that will fit the area next to the genset compartment
2) if one battery it will be 12v (duh!), if two batteries I'll use 6v
3) vent the box from the top or top edge into the genset compartment
4) live happily ever after

Thanks all!

Brad
3.5) some vent holes at the bottom of the new battery box so air can get in.

Otherwise, excellent plan.
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Old 10-16-2012, 07:17 PM   #23
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"There is enough room I might be able to get two batteries back there. The Argosy 20' mh only came with one coach battery and two would be so much nicer."

Brad, when you're shopping for a battery box, you might think about going to 6v batteries, some of which are a little taller than a similar 12v. For my van I replaced the original 2 84Ah 12v AGMs (parallel wired) with 2 120Ah 6v FLAs (series wired). This increased my capacity from 164 Ah to 240 Ah. See this post:http://www.airforums.com/forums/f240...ies-91911.html
This is stated wrong, I checked the specs for the batteries you used and they are each 6V 240AH in series for 12V 240AH.
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Old 10-16-2012, 07:19 PM   #24
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3.5) some vent holes at the bottom of the new battery box so air can get in.

Otherwise, excellent plan.
That I can do
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Old 10-16-2012, 07:54 PM   #25
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This is stated wrong, I checked the specs for the batteries you used and they are each 6V 240AH in series for 12V 240AH.
Nice catch You are correct; the new 6v batts are 240Ah each (20 hour rating); wired in series gives 12v/240Ah. My bad

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Old 10-16-2012, 10:54 PM   #26
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You asked about the size of the vent - it does not need to be very large. 1/4" or 3/8" inside diameter tubing should be plenty big enough. You are not talking a high volume of gas being generated at one time.
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Old 10-26-2012, 05:07 PM   #27
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In all honesty if you have batteries in the living quarters, Gell is the only way to go. However the charging system must match the Gell battery charge rates.

All other types will need venting not only from the battery vent but the compartment as well, hence why most battery locations are outside.

I made up a battery tray to the chassis, so it is open, but at the same time has some insulation around them for freezing conditions.
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Old 10-26-2012, 05:45 PM   #28
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So, inherently a problem, but..... how much will never be able to be determined. I am sure lots and lots of batteries are placed like yours is now, and have worked without exploding..

So, although never a great situation, the actual danger is hard to tell. What risk are you willing to take? No one can decide that for you, nor should they.
To help you manage the risk… Lower explosive limit for hydrogen gas is 4%; upper explosive limit is 75%, according to Material Safety Data Sheets (MSDS) for hydrogen, as published by AirGas, Air Liquide, and other companies that produce hydrogen commercially.

So, if the concentration of hydrogen in the air is less than 4% of the total volume of air, it won't ignite. In more practical terms, for every 100 cubic feet of interior volume in your Airstream, you would need 4 cubic feet of hydrogen gas for it to ignite. Most batteries, even traditional wet-cells, won't offgas that much hydrogen.

There is a bigger risk in a sealed but unvented battery box, because it's a much smaller volume, and you only need 4% hydrogen in the box to make it ignite if there's a spark or it gets too hot. So, if the battery box is not vented properly, you could turn the battery box into a bomb; but you wouldn't turn your whole Airstream into a bomb.

Still better to go with AGM batteries, though. Even if your Airstream won't explode, hydrogen gas is still classed as an asphyxiant; it will not do your lungs any favors if you breathe the stuff, even in small concentrations.

With regard to venting, the vent hole in the top need not be large, but needs to be at the very top of the box, and the vent hose should not dip or level out at all; it should go up all the way from the box end to the open end. You don't want the vent hose to trap hydrogen, either. The vent holes at the bottom should be larger than the vent holes at the top, or there should be more of them. In addition to allowing air in to replace the off-gassed hydrogen, they serve as drains for condensation.
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