battery box for a 2nd battery

[ubergeek]

i am thinking about adding a 2nd battery to my SMB which currently has G27, and have the following questions.
1. where can i buy a battery box with a vent?
2. how do i route the new vent ?
Thx.

[daveb]

So you're installing it inside the van?

[BrianW]

Plenty of places online have the battery boxes. Just search on "RV battery box" or something similar. Also some good tutorials out there about venting. Generally, since gas rises, you'll need to vent from the top of the box to outside, via a cutout in the van wall. Make sure the box is tightly sealed so it doesn't leak out the seams.

As daveb mentioned, though: if you aren't installing inside the van, you don't really have to worry about vented battery boxes. There's also a school of thought that if you use AGM batteries you don't have to be as concerned about venting, either, as they supposedly don't outgas.

[dig255]

What is the chemical compositionof the gas that comes out of batterys? What does it smell like?What are it's effects? how bad is it for people?
Thanks DIG

[daveb]

Originally Posted by dig255

What is the chemical compositionof the gas that comes out of batterys? What does it smell like?What are it's effects? how bad is it for people?
Thanks DIG

Basically hydrogen gas. There is practically no smell if only slightly off gassing but the gas is highly explosive with an explosive limit of about 4-72%. Its specific gravity is .070 which is much lighter than air so there is no hazard of pooling. Some batteries can produce a few toxins such as arsenic hydride and antimony hydride (while charging), but usually in such low rates its not a real problem. A failing battery is another thing and produces the standard "rotten egg smell". As a rule, that is when a battery is most dangerous.
[edit] remember that they are filled with acid, probably worse than the hydrogen and as posted AGM's don't off gas nearly as much as wet cell types. AGM's also usually won't spill acid like wet cell types can.

[dig255]

Thank you for confirming what I basically knew. Admittedly I have run a standard marine type battery inside my E150 home brew for many years and have never smelled anything or blown myself up. or burned myself it is well secured in a battery box
Thanks DIG

[daveb]

I regularly charge my batteries in my garage on my bass boat and have never incountered a problem. Not saying it can't happen.

[BrianW]

The problem is more when the battery is being charged in a small, enclosed, non-vented area like under a gaucho or dinette seat, especially if there are sources of ignition also present (inverter, etc.).

[ubergeek]

Originally Posted by daveb

So you're installing it inside the van?

Hi Dave
yes, i am adding a 2nd unit next to an existing battery inside the van.
There is a sealed battery box with a vent already connected to the wall of the van.
So my question was, given there is an existing vent that is connected to the battery box,how do I plumb the new vent out of the new box?
I know for sure I dont need two separate pipes coming out of two boxes... do i make a T pipe or ?
Thx..

[BrianW]

The way SMB set it up in my van was two separate, sealed boxes. One was vented to the outside, the second was vented to the first via a hose and a hole cut in the side top of the first box. Both boxes had big holes (like 2"+) cut through the floor, presumably for drains? Both boxes also had a ground wire for each battery running through the drain holes. It was kind of a weird setup, very messy, and took up a LOT of room under the dinette.

I added a third battery and created my own battery enclosure, getting rid of the sealed battery boxes. You can read about it here: viewtopic.php?f=14&t=9376

My home-built box is vented and fairly well sealed, but I didn't worry about the drains or anything to protect the floor, as I'm using AGM batteries and so don't have to worry too much about overflow, spills or the like (fingers crossed).