Battery venting questions...

[Martinjmpr]

I'm about to gear up for my next big project regarding our little T@B Clamshell trailer. What I want to do is put a "platform" on the tongue, onto which the LP tank, battery box and a tongue box will be attached.
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My question is: If I put the batteries inside the tongue box, do I need to make sure the box is ventilated? The batteries might be SLA or they might be AGM. Right now the trailer has a 75ah AGM 12v battery but I'm thinking of upgrading to 2 x 6v golf cart batteries (hooked up in series) which should give me over 200ah. I don't know if the 6v batteries are AGM, although I think I'd prefer that they were.
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Venting for the propane tank isn't an issue: I'm going to mount the tank outside. I see RVs with outside propane tanks all the time so IMO there's no reason to stick the tank inside the box.
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Assuming the tongue box does need to be ventilated, should I put vent holes in the top or bottom? I know with propane they have to be on the bottom as propane is heavier than air but I don't know about any gases that a battery might produce.
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Thanks in advance!

 

[dwh]

Technically, AGM is also Sealed Lead Acid (SLA).

They won't vent unless overheated enough to push the popoff valve open. That only happens during charging, and only if something goes wrong.

They vent oxygen and hydrogen, so vent up high.

 

[rayra]

negligible concern. SLA. Battery venting is a massively overblown issue. No pun intended.

 

[KevinsMap]

negligible concern. SLA. Battery venting is a massively overblown issue. No pun intended.

Ah. This subject again. Well, give such advice as you wish. And indeed, with AGM batteries safety is greatly enhanced.

But for regular lead-acid batteries? Or nonAGM SLA? Heck, even AGM's if the circumstances are right? I will simply add my own personal experience from my years as an engineer designing toys for our U.S.Navy, and from my fellow boaters and my time among the live aboards. A few off-the-web examples, and a very few words:

TAKE THIS SUBJECT SERIOUSLY

 

[KevinsMap]

Another point of view...

http://www.yachtingmonthly.com/archive/how-batteries-can-explode-and-how-to-avoid-it-3930

 

[DaveInDenver]

All the more reason to keep batteries enclosed.

But not sealed air tight (as you know). Enclosures need to be able to exchange the air if the battery does vent. Enclosure in this case is mechanically containing the event so nothing else is damaged, acid doesn't leak, etc.

negligible concern. SLA. Battery venting is a massively overblown issue. No pun intended.

Sealed is a misnomer, all lead acid can vent hydrogen and oxygen. AGM is valve regulated so under /normal/ conditions the gases recombine at the end of charging under slight pressure instead of venting to the atmosphere as can happen in a wet cell. But if they overheat, to prevent a case breech from over pressure they pop a valve.

 

[verdesardog]

The agm batteries in the tongue box on my trailer are both inside battery boxes and the tongue box is vented, why take a chance on something so easy to mitigate?