New Batteries Don't Fit

[Ed C]

Just purchased replacement batteries for my 2019 3700LK. OEM batteries would not hold a charge, even with OEM solar system. Unfortunately, the new batteries do not fit in the plastic box, as they are just a tad too large. I plan to fabricate a plywood box, and affix it so that it does not move around in transit. Has anyone else experienced this? If so, what was your "fix?"

[AZ Traveler]

There are many different size battery boxes you can buy and install.

[DQDick]

If you can't find the right size battery box from an RV or auto parts dealer look at a marine dealer they have all kinds of sizes.

[brooks340]

When I upgraded to 4 6v batteries I just bought a tote from home depot, screwed it to the floor of the battery compartment, cut a hole in the lid and attached the vent hose. It works great, for less than $30.

[432bartman]

Smart idea.

[ranch560]

Here's a company that specializes in RV battery boxes:

https://allbatterysalesandservice.co.../battery-boxes

[masterdrago]

If I change the battery box to accommodate the two 6v true deep cycle cart batteries, does the vent drain down or up? And is there any real need to be anal about sealing the cover of the box where the wiring exits? I noticed on the original box, the sealing looks really tight.

[RMcNeal]

Lead Acid batteries can give off gases and require venting to be safe. AGM do not. I don't think Lithium do not either, but I've never owned them, so not sure. It really depends upon your batteries themselves with this. Our vent is attached to the top of the battery box. Here's a link to more info.
https://www.concordia.ca/content/dam...dBatteries.pdf

[DebNJim B]

You didn't mention what type batteries you bought. As was stated, AGM batteries don't need to be vented. I replaced mine with a large 200ah AGM that didn't fit and just eliminated the box. If you are still with wet cells I think the tote from Lowe's is a good option. they have some nice heavy boxes in various sizes.

[RickyRobert]

Another battery myth - that AGM batteries do not require venting. WRONG! Not only does code (ABYC and RVIA) require that AGM batteries be vented, there is a solid reason behind it. Even AGM batteries can give off harmful gasses, albeit most likely caused by over charging. AGM batteries are built with emergency vent valves. I strongly encourage the naysayers to research this topic - it could one day save your life!

[rohrmann]

Just cutting a vent hole at the top of a box will not provide proper venting. You must provide an additional vent out the bottom to not only allow air to flow but to also drain battery fluid if a battery case fails, so the bottom hole should have a short length of pipe that clears the bottom of the compartment.

[432bartman]

I learned something new today about venting AGM batteries. I haven't reinstalled my new AGM batteries yet, and am glad I read what RickyRobert posted. Previous to reading his post, I was going to remove the vent tubes, thinking they weren't needed anymore.

[DebNJim B]

And so once again this forum demonstrates there is still more to learn.
Fortunately, my air intake in the front wall and outlet in the floor are still in tact and I can make this safe again.

[Loadone]

Ricky,
AGM Batteries do not require venting.

[432bartman]

Originally Posted by Loadone

Ricky,
AGM Batteries do not require venting.

I pulled up the two codes Ricky mentioned and it states they do need venting.

[Loadone]

432 bartman,
A Google search shows they do not. However, probably not a bad idea to be on the safer side.

[RickyRobert]

All I can say is please refine your search criteria - stay away from the "opinions" and "never had an issue" posters - go with the science of battery technology. A good starting point is https://rvnerds.com/2017/11/01/elect...-need-venting/ . There was also a post on this thread a few lines back that pointed to a University paper - good science, not myth.

[RickyRobert]

In the study paper, scroll down to the VLRA section. This covers AGM batteries amongst others. https://www.concordia.ca/content/dam...dBatteries.pdf

[RMcNeal]

As RickyRobert stated, the Concordia University paper covers AGM batteries starting on page 13. They are much less likely to vent hydrogen gas during charging, but a catastrophic failure "could" still occur in which gases will be vented through the valve. In this unlikely case, an ignition source "could" cause an explosion. More specifically, it states the following:

In VRLA batteries, any hydrogen and oxygen produced during charging does not escape but is converted
back into water. Gas can only escape when internal pressure exceeds the rating of the pressure valve.
Therefore, VRLA batteries are much less likely to release hydrogen than vented batteries. A vented
battery can give off sixty times more gas than a VRLA battery in normal use.
Water cannot be added to these batteries as they do not need topping up. However, it is still important
to take care when charging them. Gas pressure may build up inside the battery if it is charged too
quickly or for too long. If this happens, the pressure relief valves in the battery may open and let the
gases escape. An explosion is likely if this happens close to an ignition source.

These types of batteries are used in numerous applications. I am currently sitting very close to 2 in a UPS battery backup enclosed in a metal box beneath my desk. It is not vented, but is also not sealed. This is addressed in the storage section 3.3.2 on page 15, specifically:

VLRA batteries are also subject to the same NFPA 1 and IFC storage requirements, however they release
little or no gas until the battery is recharged to approximately 80% of its capacity. They create no offgassing unless stored in extreme heat. They are vulnerable to overheating if voltage and/or ambient
temperature exceed recommended levels, so normal charging regimen of any UPS is to reduce the charging rate during the last 20% of its charging.
VRLA batteries are typically used in occupied environments; the ventilation requirements for human occupancy and electronic equipment operation (e.g. in a data center or network room) well exceed the requirements for the batteries meaning that usually, no additional engineering is necessary for VRLA
battery ventilation.

That last sentence gives rise to the inference that venting is not necessary.

[jeffba]

meaning that usually, no additional engineering is necessary for VRLA
battery ventilation.

I love that line.

Kinda like saying that I am usually right. Then when I am not, the DW.. well you get the picture.