Do I need a battery box??

Our fifth came with 2 group 24's in separate vented boxes.
I wanted more battery capacity so I built a custom vented plywood box to hold 4 group 24's.
Vented out the top through the front wall of the trailer and through the metal deck of the compartment.

I went from single 12 volt to 2 12 volts. Took out the original box. Measured and got a regular plastic storage box. Cut off the vent from the original single box, and added it to the storage box top. Added some foam tape I had laying around, to the top lip of the storage box, to provide a better seal. Cut holes in the bottom to the outside for air flow (same spot as the original single box).
Secured, put both batteries in, and hooked up.
Two boxes would have taken too much room. Double box was too big and expensive.

Thanks to C Schomer and westend! Good feedback, and I'll investigate the other brand of battery box. It just might fit!

I'm more familiar with Coast Guard rules than DOT, but in any event, the main purpose for ventilation is to get rid of any hydrogen gas generated during charging. Explosions due to stray sparks (even very little ones) are a possibility. The problem that I can see is that there is little in the way of definition of what adequate ventilation means. So it seems to be an "anything is better than nothing" situation. If there ARE specifics someone knows about, I would appreciate being directed to it.
The other issue, of course, is battery acid. Most of this would come from splash outs around the caps, or dripping while checking levels. My boat has carpet burns from trolling batteries, where the acid splashed out every time we hit a wave. Mfg. only installed a tray. Those are AGMs now, which resolves the problem. But, in the rear, the starting battery is still in a tray, and as the ride is much smoother back there, acid splash has never been an issue.
Presumably RV's are like cars - the ride for the battery is orders of magnitude smoother than a boat, hence splash outs are not a concern. But I don't have much experience here, hence the questions.
As far as "fumes" - I was referring to the hydrogen. There may be a bit of additional HCL (acid) that gets in the air, leading to a mildly corrosive environment in an enclosed area. If this IS something to pay attention to, I would appreciate it being noted.
But to assume there are clouds of really bad stuff that must be kept away from occupants seems to be unsubstantiated and is not the reason ventilated boxes are used. Explosions, yes - disease from "chemicals" - no.
I have also found some cheap plastic bins at Ikea that just might do, so I'm out to the garage to see what can be lashed together using those.

This dual 6V battery box is 22 3/8" x 8 1/2" with the lid on. Hook a hose up to the top and lead it to an outside vent and you should be golden.

C Schomer wrote:
On our previous 5er I had two 6v in the front storage w/o a box for 8 years. There were no leaks to the living area and the vent hole up high was still open. The floor of that area was steel and it had lots of gaps for circulation. I strapped them down with heavy nylon belts. I NEVER saw a speck of corrosion on anything in the compartment. Our current 5er has the batteries in a small wooden compartment with a louvered door and no special battery box. There is no room to use anything to secure so I cut styro blocks to fill the gaps so they can't move much. Again, no problems or corrosion on anything. Just like auto batteries, corrosion and gassing isn't a problem when they are in good shape and charging properly. Craig

/\ This. When your batteries start out gassing alot, consuming lots of water or stinking of sulfur, they are on their way to the recycle plant. Assuming you are charging them at the correct voltage, and your car voltage regulator isn't fried and boiling the electrolyte off.

On our previous 5er I had two 6v in the front storage w/o a box for 8 years. There were no leaks to the living area and the vent hole up high was still open. The floor of that area was steel and it had lots of gaps for circulation. I strapped them down with heavy nylon belts. I NEVER saw a speck of corrosion on anything in the compartment. Even when the batteries got old and wouldn't hold enough charge to be useful and they started corroding the posts, the rest of the compartment and stored items were unaffected. Our current 5er has the batteries in a small wooden compartment with a louvered door and no special battery box. There is no room to use anything to secure them, so I cut styro blocks to fill the gaps so they can't move much. Again, no problems or corrosion on anything. Just like auto batteries, corrosion and gassing isn't a problem when they are in good shape and charging properly. I would try it w/o a box and keep an eye on things. Make sure there is high and low vent paths. Craig

How fume proof should it be? Totally sealed so it is impossible for any transfer of fumes from the batteries to the living area. NONE!

Install a small 120 vac brushless fan that pulls air from the compartment pushes it to outside. A plastic tray to contain acid drips. Open the doors when you are top charging or equalizing. Remember, hydrogen rises, lead drops.

Mine has a separate propane area in the front, with the battery only compartment on the side. Behind that is a separate basement. So I'm really asking if the compartment that only holds batteries really needs to have them in a box, or if the whole compartment can be regarded as "the box". The box would still have a vent to the outside, just not ducted from a closely enclosing box. And then there is the question about how acid/fume proof it should all be....

My batteries are installed in my Fifth Wheel Trailer just behind this front storage door to the right in an slightly recessed area. The flooring under the battery box area has open slits to allow fluids to drain to the ground under the trailer if necessary. This area is open to the whole storage area with 30LB propane tanks in a small sealed off compartments on each side of the trailer.

Having a vented battery box for each battery would be a must have for me. If this area was closed off to the batteries only then it might be a different story.

I also have an INVERTER mounted on the inside wall just a few feet away from the battery box.

If it were me I would locate a GC2 battery box that has a vent hose and houses two each GC2 6VDC batteries in the one sealed box. The vent for my battery box is to the right of the front storage bay door shown here. You can see a vent for the propane tank just above the left of the Propane Tank outside access door.



Everyone probably has different circumstances
Roy Ken