Battery ventilation

[Devo]

I have taken a lift truck battery with 2 bad cells apart.

it was 48 volts , 500 amp hours

I am going to parallel 3 strings of 6 cells (12 volts) for now.

If these are stored inside should they be enclosed in some sort of container

with a vent to outside or are they ok to sit in the open indoors (this would be the same room as the furnace)

I can also store them outdoors under the silo where the wind genny is but I am worried about the winter temperature -should I be?

On another note My dual rotor 8 mag windmill hit 20 amps a few times today at 14 volts , this is only 16 feet up in the air- going 6 feet above the 30 foot silo this week.

 woohoo :-)

Devo

[MountainMan]

Just for reference, I have four 8-D truck batteries placed in the front most bays of my motorhome and connected to my solar panels and Xantrex inverter charger.  When I put the batteries in these bays, I put in a small fan that I thought would do a great job of circulating the air in there and keeping it safe; no dice.  Whenever the heater comes on in the MH, the negative pressure inside the MH pulls enough battery gas into the MH to set off the propane gas alarm and shut off my propane.  For this reason, I have to leave the bay door open most of the time.  I'm working on some better ventilation for it as time goes on, but the point is that they do make bad gasses when they charge.  Gasses that can explode.

I would strongly urge against placing them inside in a room with your heater unless you take adequate precautions to ventilate them to the outside.

jp

[Tom in NH]

It's maddening when you read, "use adequate ventilation," but they don't say what it is. The danger is two-fold. Gassing of the batteries produces hydrogen which is explosive in the right mixture with oxygen. Gassing also causes sulfuric acid to get into the nearby environment, and that can be very corrosive to cables, electronics, and other nearby metal objects.

I once knew a guy who nearly blew his face off because he had a cigarette in his hand while he was looking under the hood of his car.

Fortunately, hydrogen's buoyancy makes it dissipate very quickly as long as it has an escape route. I think you can reduce the amount of hydrogen your batteries make by reducing the float voltage somewhat so you don't hear the batteries bubbling and boiling away.

Since my batteries are now in my basement, I, too, want to minimize the risks. I got to thinking of a system of plastic tubing where the ends of the tubes are jammed down into the battery filler holes and the other end of the tubing going through the wall to the outside. Does anyone know if there is any such beast that is available commercially? --tom

[pwr]

Besides generating hydrogen and oxygen in the right ratio to explode,

lead acid batteries also output arsine and stabine in small quantities.

You probably won't die from them immediately, but maybe later from some

sort of cancer.  Given that you're using old and probably worn out

batteries, you can expect more gaseous emissions than with new

batteries.

OSHA does not allow vented batteries in the workplace, so take that as

a clue.

[Devo]

That's good enough for me , thanks fellas - I'll put them in the barn in an insulated box & see how they hold up through the winter

Devo

[TomW]

devo;

I use a hunk of 2" PVC with a computer power supply fan that sucks air from my battery box to the outside any time there is power coming from my panels. My box is simply plywood and the PVC goes through a wall with some screen to keep critters out. The fans leads are connected on the panel side of my charge controller so any time there is voltage on the panels the box has a negative pressure in it allowing gasses to vent. The box is loose enough that air gets into the box easily. Very low tech and very effective way to allow me to keep my batteries in a warm location safely.

Just how I do it.

Cheers.

TomW

[Devo]

Sounds like a good set up , does a computer fan have brushes or are they brushless?

just wondering if there is any issue with sparks if the fan is in the tube?

I would like to keep them indoors if I can do it safely

Thanks for the info Tom

Devo

[halfcrazy]

i do the same as tom basiclly except that i have the 2 inch vent fan made for solar batteries. it gets to cold here to keep them outside

[TomW]

Devo;

Brushless and no sparks.

T

[seanchan00]

Hi,

I too intend to do that but worry about the battery running the fan when the panels/wind-gen are not producing power. How do you wire them to prevent the fan from draining the battery?

SeanChan.

[Volvo farmer]

That's odd. I've had a few motorhome heaters and they all pull the combustion air for the furnace in from the outside, that's why there's that "tube-inside-a-tube" chrome thing stuck to the outside of the RV. The center tube is for exhaust, the outer one is for combustion air. There should be no negative pressure inside because of the heater coming on. When the blower fan kicks on, it's supposed to just recirculate the air inside the RV. I wonder if something is wrong with the way your heater is vented?

[TomW]

SeanChan;

From the comment:

The fans leads are connected on the panel side of my charge controller so any time there is voltage on the panels the box has a negative pressure in it allowing gasses to vent.

The charge controller isolates the battery from the fan /panels so fan only runs when there is voltage from the panels.

A properly place diode could do the same if you don't use a controller.

Cheers.

TomW

[Devo]

Ok I have a few more question on this , when a battery is "gasing" do the gases rise

naturally or fall settling on the ground?

The reason I ask this is I want have my intake vent & wire entry point at the other

end.This is probably answered on the board already but I thought I would through it out there.

Also if they are just sitting , not charging  are they safe to put in the basement until I have the box built?

1 more , is there some kind of detector I could buy incase of a leak that would alert me?

Thanks for all the input Tom

Devo

[TomW]

Devo;

Hydrogen is lighter than air so it will tend to rise. I am not sure of the oxygen. my vent is near the top of my battery box but I don't think it is that critical as long as gasses have a way out. Not sure on the volume my fan pulls but my battery box is about 4 feet square and maybe 16 inches deep.

Somehow I think that if you put a tall pipe up above the roof it would vent naturally since the hydrogen wants to go up anyway.

Good luck on the project and err on the side of safety since all the fun goes away if you hurt yourself or ruin your gear.

Cheers.

TomW

[maker of toys]

air, from a chemical sense, is impure nitrogen; as a gas it has an average moulecular weight of about 29AMU.

Nitrogen (N2) has a molecular weight of 28AMU

Oxygen (O2) has molecular weight of about 32AMU.

Hydrogen (H2)has a molecular wieght of about 2AMU

Water vapor (H2O) has a molecular wieght of about 18AMU

in light of the above, and in general terms, and assuming absolutely still, isothermal  air, two of the gasses out of a battery (H2,  H2O) will tend to rise.  the O2 will have a slight tendancy to sink; but the tendancy is so slight that any reasonable thermal or convective current will mix the air and draw the oxygen out too. As long as you can generate a reasonable temperature differential in the 'chimney', there should be no problem with convective venting. . . . though personally, I'd use a brushless fan in the chimney, maybe with a delay circuit to run it for a little bit after charging stops, just to be sure.  

(I've seen one small fuel-air explosion [propane-air] up close, and i've no interest in a repeat. . . . 'nuf said.)

[Argie]

TomW said:

>>>my vent is near the top of my battery box but I don't think it is that critical as long as gasses have a way out.<<<

Shouldn't there be another vent at the bottom of the battery box so that clean air comes into the box to replace the gases going up, or viceversa?

[TomW]

Argie;

Well the box was built intentionally with loose tolerances so the fresh air can enter. It is intentionally not sealed very well around the floor to sides joint. Anyway yes you would need air coming in. One of those "should be obvious" things that a guy tends to not waste energy explaining.

Cheers.

TomW

[Argie]

I know of a guy who made his own battery box inside an RV, perfectly sealed (as it should be) and with a single hose hanging down at the bottom because he was told that battery fumes where heavier than air and he thought that the fumes would just drop out of that hole by their own weight, like water, without the benefit of cross flow.

It pays to spell things out sometimes for the benefit of those who may not grasp things properly, as I do myself sometimes with some other more technical issues, and instead of confusing them with details about which gas is heavier than which we should just tell them they should put one hose at the bottom and one at the top so gases are free to depart from that battery box whichever way strikes their fancy.  

[RCpilot]

TomW can you elaborate a bit on the fan system you are using? I plan to do the same method but my fan is 12v and I too want to run it from the panels but mine are in series and the voltage going into the charge controller right now with only two panels is around 38 volts in bright sun. I will be adding two more panels in series with those soon and then the voltage will be approaching 75 volts or more. That would toast the fan. Is the input to your charge controller much less? Are you regulating what your fan runs from? In my case I could see wiring a small LMXX12 regulator to the panel side to supply the needed 120ma the fan needs but I don't want to interfere with the charge controller. I don't know what would happen with the regulator wired in, I guess I could experiment. Anyway any additional info on your setup would be appreciated.

Kelly

[TomW]

RC;

Wow, 2 year old post. My system has gone from 12 to 24 volts now and I have added a turbine. I use an isolation diode block that isolates wind from solar sources. The fan simply connects to negative buss on batteries and positive buss on the source. I got lucky and found a 24 VDC fan in my considerable scrap pile so voltage matching was not needed on the upgraded voltage system.

In my system, the only time I would get enough current into my approximately 1,000 AH bank to create much gassing is if all sources are pushing at full capacity. Since that can only happen when the solar is active, I use the + from the solar to the + on the vent fan. This way, it only runs when I have incoming solar [well any daylight drives the fan] and the fan never sees more than battery volts + a diode drop.

I have been pondering what I will do next because I intend to add 2 turbines by first snow. I hope, I hope. I am leaning towards a circuit using optoisolators on the source that any, either or all sources can drive the fan by driving the base of a small signal transistor. That should give source isolation. From there you could simply use a voltage divider matched to your fan to get the proper voltage. You could always use a regulator or simply multiple fans in series to get up to the voltage you have. I think most muffin fans are pretty tolerant of higher than rated voltage.

Good luck with it.

Cheers.

TomW

[RCpilot]

Thanks TomW, I was Google searching the board for "Battery Ventilation" looking for ideas on how to trigger the fan to only run when the battery gasses when I came across this thread. I wish there were more posts, diaries that show everyone's system schematic. I plan to make up one for mine, being a fairly simple system compared to others. Anyway, you have given me some ideas to think about. I will probably take all the ideas I come across and come up with something unique but similar to others. I was thinking something in the line of a small circuit that measures the battery voltage and only kicks on when the battery reaches a certain voltage. I have noticed during the charging of my forklift battery that it only gasses a lot when it's floating so maybe a trigger circuit that kicks the fan on around 13 volts or so. Today I am going to seal the battery top up and get a vent rigged up that will at least get it vented outside of the shed and work out the trigger stuff soon.  

Kelly