Outdoor battery box venting

[mvr]

The box contains two Trojan Golf Cart batteries. It is poured in place concrete (below ground to maintain battery temp) with room for two more batteries of the larger L16s if I ever need to upgrade.  I have one Kyocera 130 watt panel with a Xantrex charge controller to charge them. The panel can max out at about 7 amps. The box has a drain hole in the bottom exiting through 1 1/4 inch PVC underground to an opening about ten feet downhill from the box.  Above the box is my cabin on concrete piers about a foot up from the top. You can see photos at www.mvr1.com if you look on the side menu for my timberframe cabin page, on the fourth most recent installment. I'll have some more photos of my panel later this week, but the box is already well-represented.

My plan was to stick a 1 inch vent pipe up out of the box and let the relative weight of the Hydrogen direct it out the vent. Input conduit is inserted well into the box so that it is hopefully below the level hydrogen wants to go, and in any case I will use foam or something to seal these now that the wires are in place. I've gotten differing advice on how to vent it. One person suggests I go with 3 inch pipe all the way up above the roofline.  This will be ugly and will cause a few problems with the snow taking out the pipe.  Cumulative snow load is over ten feet per winter.

I don't really want to use a fan as I'm not sure I can spare the power in my pretty well treed location.  My thought was that in an underground box not attached to the cabin I could get away with a 2 inch pipe that vents above the base of the cabin, but below the roof.

I've read the prior posts on venting. Any thoughts?

Thanks in advance for any help.

Mark

[mungewell]

Hi,

Nice looking cabin.

Not directly related to your specific question, but this is as good as place as any to add to the discussion of underground battery boxes.

I remember reading a Mother Earth News article on underground green houses, that is ones which were dug into a hill to get temperature sheltering. One major feature of these was the walking in bit, next to the 'bed' was quite a bit deeper and acted as a cold sink. Any cold air entering the green house was heavier and fell to the bottom of the pit where is was out of the way of the plants.

Perhaps a similar idea could be used to auto-circulate the air from the bottom of a hole, without having to place the batteries at the bottom.

Simon.

[luckeydog]

I believe 1 1/4 inch pvc will do you just fine.

4" is a bit large and may let in so much cold air that it would defeat

the purpose of having the geothermal heat.

their is not a lot of hydrogen gas released by 2 batteries and the

hydrogen gas being lighter than air will travel up out of your

battery box with out any problem. it would take weeks and even months

to accumulate even 1 liter of hydrogen depending on your charging

practices.

just my 2 cents

Luckeydog

.

[mvr]

Thanks Simon for the kind comment and the info!

My thought was that the heat from the ground would keep the batteries warm enough to keep working even in winter.  I'm at around 9200 feet elevation, but the frost line tends to be very shallow because of the snow insulating the soil.  My though was to insulate the top of the box and thereby to keep the batteries at around the freezing point of water and well above the freezing point of the electrolite in the batteries.  So I'm thinking that in the winter the ambient soil temp will warm the batteries so being closer to ground is better.  In the summer I think we'd get the opposite effect but at that time keeping the batteries warm enough won't be a big concern.

Mark

[mvr]

Thanks for the twoi cents!

Mark

[nothing to lose]

Ya, hydrogen is lighter than air, so it wants to rise. You aren't making that much either.

 My thought for such small battery space is the guy saying 3" to the roof is plain nuts.

First, hydrogen wants to rise. Second during winter the gases from the batteries in storage like that should be warmer than ambient air, warm/hot air wants to rise.

Any ambient air in winter is probably colder than the battery space, so it wants to drop.

Depending on the discharge and rate of charging you may not be making enough hydrogen to even worry about really, any venting should be fine.

There should not be any sparks, flames, etc in the battery area.

If it were me I would run maybe 3/4" pipe in and 1/2" out, keep it away from windows near a fire source like the wood burner, and run it about 2' above the box/ground.

In summer you lose ambient cold air warm air flow, but for just a couple batteries it should not matter, hydrogen still is lighter than air and wants to rise.

Do you run a 3" pipe 20' in the air to vent your car battery?? Of course not, and it probably produces far more hydrogen than your storage batteries! And with a faulty wire it's right next to igniting sparks also! On this point I shall say today was a rough day for me. My truck has a starter flywheel problem, worse when hot and engine stiff. So I got stuck for 2 hours today, crank, sit, crank sit, ran battery low and was jumping from a booster pack. So it finally started with maybe an 11V battery, I found a bad wire sparking, 100 amp alternator charging high, never blew it up! I did of course replace the wire when I got home. Point is, that battery was probably making more hydrogen at heavy charge for an hour than 4 of my L16P trojans in normal use, and it had a spark close by.

BE SAFE. Don't be paranoid though.

[TomW]

dog;



their is not a lot of hydrogen gas released by 2 batteries and the

hydrogen gas being lighter than air will travel up out of your

battery box with out any problem.



Not only that, but I doubt you could even contain the hydrogen for any length of time if you wanted to.

I also agree on the pipe size comment. I use 2" with a double 90 degree elbow on the top to exclude rain. [looks like an upside down J].

Cheers.

TomW

[WindChopper]

You might want to take a look at railroad signal battery boxes.

As I recall every railroad line signal, road crossing signal, etc. has a battery box attached to it, usually underground as I believe that the signals / gates are battery operated.

As an example a quick Google of "Railroad signal battery boxes" found:

http://prr.railfan.net/signalstandards/standards.cgi

Scroll down to the S5xx drawings for some samples of old version drawings.

You might also want to search out some more recent versions or make friends with your local railroad signal shop for more current information.

I figure that these people have been hiding batteries underground for a hundred years or so and may have a few time proven ideas.

Just a thought ....

Russ

[toothy]

Hello

I have no real knowledge about this but I never let that stop me!

It seems to me that your low high venting would cause a chimney effect.

In the winter you may get more flow than you really want and it may be a detriment to the geothermal effect. One out the top and let molecular weight take it's course.

Later

wade

[mvr]

Thanks Russ, I did take a look.  Looks like the put a vent near the top with no assitance from a fan.  Pretty simple.

[mvr]

Thanks for the input.  I'm kind of on this wavelength myself.  best, MArk

[mvr]

Thanks for the response.  It seems to fit what a lot of people think and is useful to hear.

[mvr]

Thanks Wade!  I appreciate the response.

Mark

[Ungrounded Lightning Rod]

You can fix that by putting (ONE!) drain-style trap in the drain pipe.  That will let water out but block airflow.  (That's what they're for in drains, too.  B-)  Keeps the sewer gas in the sewer.)

Pour a couple cups of water into it to establish the seal and do it again every few months to replace water lost to evaporation if you don't have a leak into the box or enough condensation to keep it filled.  

Of course you'll want your trap to be below the frost line so it doesn't freeze and break.

[mvr]

That's a clever idea, though I don't think I can impliment it any longer without a lot of digging.  The drain line is long enough that I expect the soil to warm the air in it a bit before it hits the box interior, and it is only a 1 inch tube so it won't let in huge amounts, especially in winter when it will be snow covered at the open end.  But still the idea is a good one that I might work with if I were starting over from scratch.  Thanks for the suggestion!

[RogerAS]

Signal Box, eh?

Like this?

C y'all,

<|:-o