Show Me Your Battery Boxes

[SouthTX]

Search on "hydrogen" in the search tool in the upper right corner. One example https://www.mygrandrv.com/fo...light=hydrogen
Follow the various links to what can happen . . . there is a valid reason that the OE batteries are vented outside the trailer.

Rob

Rob - perhaps this item deserves more discussion than it has received (if that is possible ). My apologies that I haven't had time to write up everything that I've learned in the last day, but it appears there are some serious shortcomings in the OEM venting system that make me question if it is better than nothing.

I haven't seen anyone who seemed impressed by any RVIA standard so I looked at the FAA standards for light aircraft. Light aircraft generally have a battery powered DC power system not unlike what is found in RV's and these standards have been adopted through a formal process including all stakeholders. Generally, these standards are very conservative.

In short, 14 CFR 23 requires venting, but doesn't address how it should be done other than to require that it prevent the buildup of explosive gasses. For the how to do it, the FAA publishes Advisory Circular 43.13-2B. Basically, it allows two means of compliance. 1. a compartment with sufficient air exchange that no buildup of explosive gasses is possible; or, 2. a "sealed" battery box with "flow through" venting. Presumably, this type of system would include an air scoop to pressureize the vent system and flush the gases out an exhaust vent.

With this as background, consider the typical RV battery vent system. A single tube to allow lighter than air gasses to flow up and out of the compartment. There are a couple of problems, though. How much airflow will you get with only an exhaust port (no intake port) from a (semi-?) sealeld battery box? Often the tubing used in these vent systems (and I use the term loosley) have low spots that would block the flow of lighter than air gasses. And, perhaps most shockingly, this (forward facing) exhaust port is actually pressurised when the vehicle is underway and there is no route to exhaust gases from the battery box.

Again, my apologies for not having time to provide excerpts and links to some of these documents, but I think you can understand the problems here. I agree with you that battery boxes need to be ventilated, but OTOH, some of the OEM vent systems I've seen - including on my 337 - appear to not only be pretty ineffective. But under certain circumstances may actually contribute to the buildup of an explosive mixture.

This is not a simple issue. Just running a pipe to daylight is not an answer.

Best,

John

[CoChris]

Interesting. In my 2018 Solitude there is both a vent in the lid leading to the vent opening higher up the front wall (pretty standard from what I have seen) AND a vent in the bottom of the battery box through the floor to daylight under the trailer. Is this not standard? Something new for 2018? Only in the Solitudes? I do wounder how effective the bottom vent is as it is close to the center of the box and the battery covers it (but it is not sealed).

Chris

[Cate&Rob]

John - I would agree with your assessment of RVIA. My experience is automotive, marine and residential . . . and trailers built to "RVIA standards" would not come close to the expectations and requirements in any of these industries. It does not surprise me that comparison to the aviation industry points out even more RVIA shortcomings.

I am definitely NOT trying to endorse or explain what RVIA requires, but as Chris points out the battery ventilation system has an opening below the battery so that there can be inflow of air to allow the upward flow of hydrogen. At least, that is how I understand the theory. I have never been able to find a RVIA document that explains this . . . and I have looked. I have even asked GDRV and have been told that these requirements are available only to the RV manufacturers. The "fox guarding the henhouse" analogy comes to mind.

I have also questioned (in previous discussions on this forum) . . . why is the outlet facing forward? Some have speculated that when underway, this becomes the air inlet and flushes the battery box in a downward direction and out the vent below the battery. As Chris notes, the opening in the bottom of the box could easily be blocked by the bottom of the battery. I suspect that we are seeing the typical RVIA attempt at something. The upper front vent location is the easiest one available and the battery box bottom half is exactly the same part as the upper half, so cheapest manufacturing cost.

I think we all agree that capturing a potentially explosive mixture in a compartment with many sources of ignition is something to be avoided. In a comparable marine example, all electrical devices have to be "ignition proof" and there are forced ventilation requirements when operating. Having noted this, there are also many many boats out there with batteries under sleeping berths just like there are trailers with batteries in unvented compartments. I have never seen actual reports of explosions proven to be from hydrogen gas buildup . . . but, RVIA standards are so minimal in all areas . . . they must have some reason for requiring RV manufacturers to put in these rudimentary venting systems.

Good discussion . . .

Rob

[Darlin]

Check these out.http://www.centuryplastics.ca/index....&id=8&Itemid=7

[Paul & Deb]

Check these out.http://www.centuryplastics.ca/index....&id=8&Itemid=7

Thanks Darwin, they have a box I've been looking at that holds 2 6 v batteries end to end. I would just need to get 2 which is actually fine. I'm just trying to figure out how I would vent them.

[SouthTX]

Thanks Darwin, they have a box I've been looking at that holds 2 6 v batteries end to end. I would just need to get 2 which is actually fine. I'm just trying to figure out how I would vent them.

Those are good looking boxes. Nice find, Darwin.

Rob has just about shamed me in to venting the two black plastic boxes I've installed. The vent tubing is there, I just have the same problem finding a way to attach them. I'm thinking of a threaded to slip PVC connector the same size as my existing vent tubing. A hole saw will give me a good tight hole that I can thread the fitting in to and a little PVC cement should soften the fitting enough that its not coming out.

Something else for my roundtuit list.

[TheLexx]

I'm reading this thread with great interest. My 2 lead acid batteries have so-called vents on them but I just don't see how the outgassing will completely clear the vent tube unless there's an incoming flow of air to flush it out. OTOH fortunately we haven't seen reports of gas explosions.

I'm interested in seeing what solution you knowledgeable folks come up with.

[Darlin]

I use electrical conduit for venting.t

[Darlin]

Sorry there upside down the box hold 4 6volt Trojan t125

[Cate&Rob]

The vent tubing is there, I just have the same problem finding a way to attach them.

Hi John - If you have access to a marine supply place, they will have "thru hull" flanged fittings of exactly the hose diameter that you need. BTW . . . we obviously approach these things in a similar manner . . . good discussion!

Rob