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Venting Battery Bank

HARG Hunter

Thirsty for Off-Grid Knowledge
Joined
Jul 10, 2020
Messages
210
Location
Iola, Wisconsin
Our cabin is almost completed.
I do have my solar panel hooked up and it's charging my SLA battery bank.

We haven't finished the interior of the cabin, so I've been able to get away with charging the battery bank without a final vent system.
Right now it can vent through the roof vents, but when I get the drywall and insulation in, I'll need to find a way to vent it.

I'll be storing the battery bank in a oak box with a hinge that I'm building to hide them.

What are your thoughts on this plan:
I'm thinking of putting a PVC conduit hidden in the wall.
I would put a hole in the box and the conduit would carry the gas through the wall into the attic and lead to the roof vent.

Would the gas find it's way through that vent, or do I need to propel it with an exhaust fan of some sort?

Thanks in advance.
 
Can you directly vent through wall with PVC (oak box to exterior)?
No fan. Short distance.
SLA should not require venting, but be sure your float charging voltage is not excessive.
 
Would the gas find it's way through that vent, or do I need to propel it with an exhaust fan of some sort?
Yes, any gasses would escape this way (remember, Hydrogen is lighter than air) and No, you wouldn't need a fan.

Just for clarity, SLA batteries do not, under normal operation, expel any gasses ... they only vent when there's a problem i.e. pressure build up beyond a threshold. Flooded lead-acid are different.

Also, to be safe, your battery box should be both acid resistant and leak-proof ... not sure an oak box would do this for you. Maybe line in with PVC or polyurethane sheeting?
 
This cabin will go weeks at a time without us being there, so I thought to be safe I'd vent it in case there was an issue with charging.
We do have a Renogy Rover Elite MPPT charge controller with a temp sensor, so I would hope that if there were issues the controller would shut things down.

The main reason I thought of venting up through the roof through an extended PVC conduit instead of directly venting outside, is that we're in Northern Wisconsin, so temps will start getting pretty cold in October/November when we'll be there a lot. I figured the batteries would not be subject to the cold temperatures as much with the longer vent instead of a direct vent through the wall.
I know physics will still bring the cold air down the vent, but the intensity of cold air and wind would be mitigated somewhat through this method. It would also reduce heat loss, as the cabin will have propane heat, but the attic will be vented with gable vents.

tictag - I do plan on lining the oak box for sure. I'm just hoping to make it look like it's part of our entertainment center, as our power center will be in the corner of the living room where the TV will be. I just to figure the long term size of the battery bank so I can plan for expansion. Suggestions on materials I should use for a liner?
 
You can find inexpensive battery boxes at Walmart and auto stores. One for each just to hold the acid in case of catastrophic failure. You might find one Sterilite box that would fit both batteries. Don't need a lid. Let's see some DC fuses.
 
A proper battery box might well be your better option (and likely cheaper), I mean, it can inside the oak box for improved aesthetics.

In terms of lining, anything PVC, polyurethane, polyethylene or synthetic rubbers like neoprene sheeting should be fine - just has to be acid-resistant. A quick amazon search returned lots of options.
 
You can find inexpensive battery boxes at Walmart and auto stores. One for each just to hold the acid in case of catastrophic failure. You might find one Sterilite box that would fit both batteries. Don't need a lid. Let's see some DC fuses.

good point on the individual boxes. No need for anything special and it'll be cheap.
I do have several fuses planned.
The inverter already has a fuse and I plan to add another as well.
 
If you're looking for a powered vent, there are three on this page: https://www.solarpanelstore.com/collections/battery-accessories

Here's a description from one of them:
The Power Vent provides positive venting of a battery box. The battery box fan's built in back draft damper stops cold outside air from entering the battery box. The Power Vent can be easily installed in a battery box vent system using 2 inch PVC pipe. Many inverters and charge controllers have a 12 volt powered relay that can power the Power Vent. Power consumption is 3 watts. Air volume movement is 4 to 6 cfm. 24 and 48-volt fans are also available. The solar battery box venting fan is replaceable.

*The POWER VENT is designed around typical home power systems with battery banks under 2,200 amp hours and charge rates under 150 dc amperes. Systems larger than this can produce more hydrogen gas than the expel rate of the POWER VENT which operates in the 5 to 8 cubic foot per minute range. Two battery box fans may be used for higher volume.
 
Fuse need to start at the battery positive terminal. The fuses in the inverter protect the small stuff internal to the inverter. Our fuses protect the cables from short circuits.
 
This cabin will go weeks at a time without us being there, so I thought to be safe I'd vent it in case there was an issue with charging.
We do have a Renogy Rover Elite MPPT charge controller with a temp sensor, so I would hope that if there were issues the controller would shut things down.

The main reason I thought of venting up through the roof through an extended PVC conduit instead of directly venting outside, is that we're in Northern Wisconsin, so temps will start getting pretty cold in October/November when we'll be there a lot. I figured the batteries would not be subject to the cold temperatures as much with the longer vent instead of a direct vent through the wall.
I know physics will still bring the cold air down the vent, but the intensity of cold air and wind would be mitigated somewhat through this method. It would also reduce heat loss, as the cabin will have propane heat, but the attic will be vented with gable vents.

tictag - I do plan on lining the oak box for sure. I'm just hoping to make it look like it's part of our entertainment center, as our power center will be in the corner of the living room where the TV will be. I just to figure the long term size of the battery bank so I can plan for expansion. Suggestions on materials I should use for a liner?
I used plaino, on sale from cabelas for $15.
 
You could put the battery box under the cabin just below the spot where they are now. Access hatch through the floor, with the box partly buried to help provide insulation. Drill a few holes, put some screen over them, and you get some cool points at the camp.

Second Look at the Pic,, maybe on a slab.
 
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You could put the battery box under the cabin just below the spot where they are now. Access hatch through the floor, with the box partly buried to help provide insulation. Drill a few holes, put some screen over them, and you get some cool points at the camp.

Second Look at the Pic,, maybe on a slab.

Correct - Concrete Slab.
 
Fuse need to start at the battery positive terminal. The fuses in the inverter protect the small stuff internal to the inverter. Our fuses protect the cables from short circuits.

So basically put a fuse between the Battery Positive and the inverter?
You have a link to the right type of fuse?
Otherwise you can PM me as well.
 
So basically put a fuse between the Battery Positive and the inverter?
You have a link to the right type of fuse?
Otherwise you can PM me as well.

I use a Bussman 185 type breaker between my inverter and battery. Blue Sea calls it a 187 I believe. There is also a 285 model that is marine rated.

My inverter documentation was clear enough on the fuse/breaker required that I went with what it said. Then length of the wire run and the inverter max draw will dictate the size of the breaker. My weenie inverter is only 1000 watts and the cable run is short, so 150 amp breaker was what I used.
 
Flooded lead acid produce hydrogen gas. It's not really toxic and you need massive amounts to blow anything up.
Nothing two batteries should be able to emit into the room.

Just drill a whole through the wall - straight piece of PVC at the top of the box and done.
Don't forget the bug screen. Those creatures for some reason like batteries.

If the battery box is well sealed there should be not much air exchange. So your concerns with cold batteries are not critical, no matter how long the PVC pipe is.

If the battery box is leaky then don't even bother venting outside.
 
you need massive amounts to blow anything up.
Nothing two batteries should be able to emit into the room.

Please check the explosivity % range of hydrogen, it's wide... Also hydrogen tend to detonate when ignited, even when not under pressure.

Be very careful with hydrogen, please.
 
Please check the explosivity % range of hydrogen, it's wide... Also hydrogen tend to detonate when ignited, even when not under pressure.

Be very careful with hydrogen, please.

It absolutely is dangerous in small enclosed spaces I agree. Yet it diffuses through everything. It's really hard to contain that stuff. I worked with Hydrogen Cars and I've got literary hundreds of UPS with SLA batteries in my Computer labs and Server rooms.

If this would be flooded Lead Acid, maybe a different story. But the amount an SLA produces, it is possibility ? yes Is it probable? you decide.
 
Please check the explosivity % range of hydrogen, it's wide... Also hydrogen tend to detonate when ignited, even when not under pressure.

Be very careful with hydrogen, please.

Definitely why I am going to vent, despite the low emission from SLA's.

I have built this cabin myself from the ground up, and it's easy for me to put things like this vent in now while the walls are open, so I figure why not? FLA's may end up being something that works it's way back into the picture. Doubt it, but who knows. I might as well prepare for everything right now. I'm going to stick with my original plan.
 
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