Author Topic: Venting sealed battery box, run fans continuous or?  (Read 12787 times)

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Mary B

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Venting sealed battery box, run fans continuous or?
« on: December 14, 2014, 05:24:03 PM »
Getting ready to seal up my battery box and vent outside. Plans are to pressurize it with a pair of tiny 24cfm 24vdc fans that draw .08 amps each. Would you set it up to only run during daylight charge hours or run continuous? Be a 4watt draw so not huge but not tiny either... I was thinking of getting a cheap 24 volt panel to stick on the porch roof to power the fans during the day when the main panels are charging, or else run a separate dc supply off mains is another option, switch it over to off battery only during power outages.

offgrid1

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Re: Venting sealed battery box, run fans continuous or?
« Reply #1 on: December 14, 2014, 08:46:36 PM »
Seal up battery box? Outside? Why?

How much gassing? Fire danger? Inhalation?

None of my NiFe, Ni Hydride, or lead acid batteries are sealed and forced air vented. Hybrid cars and aircraft are the only place I've seen venting used.

Mary B

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Re: Venting sealed battery box, run fans continuous or?
« Reply #2 on: December 15, 2014, 01:38:51 AM »
My battery box sits about 6 feet behind me in the living room in what will double as a bench. And it is a sealed box so it needs venting.

Mary B

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Re: Venting sealed battery box, run fans continuous or?
« Reply #3 on: December 15, 2014, 01:50:08 AM »
In this pic the charge controllers and inverters are sitting 3 feet above the batteries on the wall, lead acid off gas a LOT when charging and especially when equalizing. So the box has covers to contain fumes.


bart

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Re: Venting sealed battery box, run fans continuous or?
« Reply #4 on: December 15, 2014, 06:55:39 AM »
   Since it is inside, my vote is to run fans all the time.

Bruce S

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Re: Venting sealed battery box, run fans continuous or?
« Reply #5 on: December 15, 2014, 11:28:05 AM »
FWIW: I wold setup a small separate panel to run the fan(s) during the day during the charge cycle.
OF course it would be nice to have a small NiCd/NiMh battery to let them run throughout the night, but since LA batteries out-gas during charge modes then venting it needed during those time plus a little afterwards.
Nice looking setup too!

 
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mab

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Re: Venting sealed battery box, run fans continuous or?
« Reply #6 on: December 15, 2014, 12:20:01 PM »
The good thing about lead-acid battery gassing is that it's hydrogen (and oxygen); unlike propane and butane that tend to hang around and pool in closed spaces, hydrogen diffuses very quickly (very small molecules), and you'd have to seal the box very well indeed to keep hydrogen in it for any length of time.

So if it were me, I'd want to run a vent fan when equalising - but it's probably easier just to run the fan when charging so I'd just do that.

The main thing it to be sure there are no sources of ignition (bad connections or fuse links that may 'blow' for e.g.) inside the sealed box as the hydrogen/oxygen mix is rather explosive if concentrations do get high enough.

madlabs

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Re: Venting sealed battery box, run fans continuous or?
« Reply #7 on: December 15, 2014, 01:08:12 PM »
I don't think you need fans at all, just proper venting. I have worked a bunch with hydrogen building a fuel cell robot. The problem isn't preventing build up, the problem is holding onto the hydrogen in the first place. Very slippery stuff, it just disappears in spite of your best efforts.

So a vent at the highest point and a vent at the lowest point and you are good to go, hydrogen wise. I think that heat build up is a greater issue in some cases anyway. Mt batts are in a shipping container and I put large (1.5") holes through the floor in-between each battery. Then a large vent out the top. On a warm day you can feel the air flow.

Jonathan

Mary B

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Re: Venting sealed battery box, run fans continuous or?
« Reply #8 on: December 15, 2014, 06:42:44 PM »
Another issue is acid fumes, hence the vent outside. I do not want that rising up into my charge controllers/inverters. Still adding things so junction panel is open, need to move the cables from the battery charger for cloudy days inside there. And I am running new conduit to the inverters so they are wired direct to the batteries and not the junction box. Second charge controller needs to be wired in along with the relay controller. Those are my winter indoor projects before I add the next 8 solar panels.


thirteen

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Re: Venting sealed battery box, run fans continuous or?
« Reply #9 on: December 16, 2014, 01:51:14 AM »
Timer for the fans might be an option rather than run them 24\7.  Also as option for manual turn on for fans if charging with a genset during off regular hours. Looks nicely done. 13
MntMnROY 13

Mary B

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Re: Venting sealed battery box, run fans continuous or?
« Reply #10 on: December 16, 2014, 02:04:39 AM »
Be easy enough to add a relay off the power feeding the charger to drop the fans to the batteries instead of a separate smaller panel. Want a panel for outdoor lighting at night anyway so something in the 50 watt range and a small deep cycle boat battery is going into the front porch to feed a motion sensing LED spotlight. Slowly taking more and more of the house off grid, second inverter is going to feed a freezer converted to a fridge, other is going to feed the deep freeze. Corn stove I use for heat is 12 volt so it is running off the 35 amp 24:12 volt converter that feeds my ham radio gear. Then add more 24 volt lighting around the house for power outages like tonight. Was on battery 100% for 3 hours.

madlabs

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Re: Venting sealed battery box, run fans continuous or?
« Reply #11 on: December 16, 2014, 12:25:28 PM »
Ain't it sweet to be on your backup?!

Just wondering: Are you going to put your fan on the input or output of your box? Seems like if you are concerned about acid fumes that if you put the fan on the input it won't be exposed. Relay off the charger sounds good.

Still, with just passive venting I don't seem to have a problem, 16 golf cart batteries. I do have lots of passive venting though.

Jonathan

bart

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Re: Venting sealed battery box, run fans continuous or?
« Reply #12 on: December 16, 2014, 03:37:25 PM »
   Something to be aware of is if you have any exhaust fans and creating a negative pressure in side the house. I.E. bathroom or kitchen exhaust fans. Do you have have combustion air provided for your corn stove?

Mary B

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Re: Venting sealed battery box, run fans continuous or?
« Reply #13 on: December 16, 2014, 05:42:52 PM »
Corn stove uses outside air, only way to install them and it is not recommended to use inside air because it can cause burn problems. As leaky as this old house is I am not to worried about negative pressure either. If it seems to be an issue I can run intake vents to the fans from the front porch.

I am going to pressurize the box not draw from it. No way would I put a fan in a possible explosive air stream from the batteries. Explosion proof blowers were way to expensive, to small 24 volt fans were $10 shipped.

bart

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Re: Venting sealed battery box, run fans continuous or?
« Reply #14 on: December 16, 2014, 06:23:10 PM »
   All I was trying to point out is anytime the battery exhaust fan is off and another house exhaust fan is on, air could be drawn from the battery box and into your living space.
  Know all about them drafty houses. Don't need any combustion air for the wood stove.

Mary B

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Re: Venting sealed battery box, run fans continuous or?
« Reply #15 on: December 17, 2014, 04:39:29 PM »
Parts of my house were built in 1880, the floor beams are logs... I have spray foamed everything and I still have air leaks. Plus the house shifts from freeze/thaw and doors never fit right. With fans on I would not worry to much but I can also add a valve that operates via air pressure to prevent reverse airflow.

hiker

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Re: Venting sealed battery box, run fans continuous or?
« Reply #16 on: December 17, 2014, 09:09:16 PM »
Parts of my house were built in 1880..

cool  ..any picts.
WILD in ALASKA

Mary B

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Re: Venting sealed battery box, run fans continuous or?
« Reply #17 on: December 18, 2014, 12:07:48 AM »
No pics, interior has been gutted and remodeled, all new windows/doors, inch of foil faced foam board then new siding over that... plus it has been added onto 5 times so none of it looks original.

offgrid1

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correction for Mary B Re: Venting sealed battery box, run fans continuous or?
« Reply #18 on: December 18, 2014, 12:49:58 AM »
For some reason the details of your battery box were not seen by me on Fieldlines. I apologize....and considering the size of your battery box and the potential for gassing it is obvious that outside ventilation is needed. As there are times when gassing peaks during charging, the rate of box purging should be at it's peak then as well. Probably, several 4" computer fans to run on demand and maybe a smaller one to run continuously is a good idea. Hydrogen out gasses and can explode so do not allow any possibility of it's ignition by arc, spark, or fire either inside or near the outside vent. A very interesting project so I'll look it over and maybe comment further.         

offgrid1

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Re: Venting sealed battery box, run fans continuous or?
« Reply #19 on: December 18, 2014, 12:55:26 AM »
Must be ventilated to outside the living space.......show details if you can.

Mary B

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Re: Venting sealed battery box, run fans continuous or?
« Reply #20 on: December 18, 2014, 05:13:00 PM »
I have a 2 inch vent entering the box at the center rear. The 2 center ribs are drilled along the top for ventilation into the center area also.

The 2 white ribs that run front to back to reinforce things are drilled along the top with 24 1/4 inch holes for venting to the center



The large grey conduit is outside venting. I will have s small 24cu feet per minute fans blowing during the day running off their own solar panels. The box is only 27cu feet so it is more than enough air turnover and enough to prevent a back draw I hope. If not I get a little larger fan.  I ran a calculation and the 2 inch vent tube is more than adequate in size to handle that airflow. Lids are just resting in place, box is still venting to the room and I have not been using the batteries very heavy to keep charge needs down. Picking up last of gasket material and some hinges tomorrow to  get the lids attached and box sealed up tight. For now fans are running off a 24 volt wall wart power supply. I need to get a smaller 24 volt panel for the fans and my outdoor lighting needs that will have their own battery and charge controller. Fans will run during day for now. I have not decided if I will put a valve on the vent to prevent reverse air flows or if I will just run the fans 24/7

The center section is hinged to allow conduit access plus I have take off taps on the bus bars in the center for easy access.


Bruce S

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Re: Venting sealed battery box, run fans continuous or?
« Reply #21 on: December 19, 2014, 09:33:06 AM »
NICE looking setup !!
Not sure how the vent look outside, but I think I'd be worried about the varmits getting into the vent.
I had to put a metal wire mesh on my vent to keep the squirrels and field mice away from the pass-through wires.
Not sure why they are so attracted to the wires or if it's the warmer air.

 
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Mary B

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Re: Venting sealed battery box, run fans continuous or?
« Reply #22 on: December 19, 2014, 03:24:06 PM »
Piece of 1/2 " hardware cloth inside the end. I figure it will rot from acid fumes every couple of years but it is a cheap replacement. Outside vent, gave it some rise to try and create a chimney effect


bart

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Re: Venting sealed battery box, run fans continuous or?
« Reply #23 on: December 19, 2014, 06:30:16 PM »
    Code requires nearly all venting to be above the roof line and 2' higher than anything 10' close to it. And if you get strong wind on that side of the house, I pray you have a very strong exhaust fan. I really don't like this.

offgrid1

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Re: Venting sealed battery box, run fans continuous or?
« Reply #24 on: December 20, 2014, 12:00:15 AM »
I like it! Initially thought 2" was too small and the circulation might leave some hydrogen pockets but you're making sure no arcing can be inside. Minimizing the hydrogen buildup with a 1" continuous fan outside normally and one or two 4" fans when things are spittin' and poppin' should do it. Outside vent looks fine. Even in the unlikely event a hydrogen pocket might ignite in the box it will likely not injure anyone. (I accept no responsibility for my FREE advice :-)

Mary B

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Re: Venting sealed battery box, run fans continuous or?
« Reply #25 on: December 20, 2014, 05:24:59 PM »
No direct wind into that side of the house, as far as code goes there is not code for venting a battery box. This is not a sewer line, I am dumping battery fumes. with 48cfm of air pressure on a 21 cubic foot box air turnover will be pretty high so a buildup is very unlikely. If I need bigger fans I can go to them but the object was to use the minimum needed to keep power draw down.

offgrid1

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Re: Venting sealed battery box, run fans continuous or?
« Reply #26 on: December 22, 2014, 01:12:20 AM »
For awhile.....watch, sniff,  and look for any hot terminals or any other weirdness. Coat terminals with axle grease as the acid will eventually crawl up the terminals and corrode the terminals without vaseline  or something on them. A plastic sheet hanging down to keep splashing of acid off wiring, terminals will be needed.   

Mary B

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Re: Venting sealed battery box, run fans continuous or?
« Reply #27 on: December 22, 2014, 12:28:11 PM »
plastic sheet hanging down?