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Old 16-08-2009, 17:52   #1
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Equalization: How Dangerous?

I am wondering if any one has had any really dicey situations with equalizing their batteries ? The warning on my inverter charger sounds pretty scary. Exactly how well Ventilated does the area need to be when I Start the process? They say it takes eight hours, am I going to need to not cook down below while I do this?
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Old 16-08-2009, 18:09   #2
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Sometimes these warnings manufacturers come out with sound more frightening than reality.

Equalization produces hydrogen which of course is explosive. As you know though hydrogen rises. The goal is to equalize in a space where the hydrogen can rise upwards to the outside atmosphere. Remove your battery box covers if they are not well ventilated and remove any deck hatches or other covers over the space where the batteries are stowed. Do not have any ignition sources in the area.
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Old 16-08-2009, 18:39   #3
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Not with 12v batteries, but I've quite literally blown up NiCad packs by overcharging them. Boil up a 12v battery during equalization, and you get the same thing in a much much larger version, accompanied by a spray of hot acid electrolyte if you manage to generate a gas explosion. A number of folks do that every year while simply jump starting cars, too.

So...the manufacturers want you to have a little fear. And eye protection, just in case.

As long as you follow directions and don't forget you're cooking something, you shouldn't have any problems.
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Old 16-08-2009, 20:39   #4
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I heard you are meant to leave the lids off of the batteries so that the gas can't build up in there. They say to just throw some paper towel over the top.
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Old 16-08-2009, 21:16   #5
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It's no use trying to prevent ignition sources; you are charging a battery, that's electricity & amps flowing and none of it "ignition protected". Not cooking isn't helping when the environment would be that explosive and just a static spark could set it off.

IMO, the best way to deal with it is to make sure the concentration of hydrogen is close to zero. We do this with forced ventilation in addition to natural convection. We set up a couple of big fans and take the fill-caps off the batteries so nothing builds up much inside the batteries either. I think the most trouble happens when the batteries themselves explode, either by hydrogen igniting or a short of the plates.

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Old 17-08-2009, 05:30   #6
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The goal of any hydrogen ventilation system is to keep the concentration below the Lower Explosive Limits of 4% - usually specified at < 1 or 2% b.v. (depending upon the authority).
During normal battery charging, between 10 - 20 cubic centimeters per hour, per battery, may be released. To achieve a 1% hydrogen concentration, this must be mixed with 99 times its volume of air, or 1,980 cc/hour/battery. To maintain a concentration below 4%, over 480 cc/hour/battery of air must be mixed with the hydrogen.

During thermal runaway, the need for ventilation depends on how many Watts the battery charger can pass into the batteries. Each Watt can produce up to 3.4 cc/min or 204 cc/hour, requiring about 20,200 cc/hour per watt of air to maintain a 1% mixture, or 5,000 cc/hour per watt of air to stay below a 4% concentration.

Batteries are designed to emit gas (which is our problem), when internal pressures build up, and probably don't require "caps off" to prevent dangerous internal pressures.

See the BCI Recommendations:
http://bci.dev.web.sba.com/private/W...ionUPDATED.pdf
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Old 17-08-2009, 06:35   #7
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When I equalize my 1200Ah battery bank the sulfur smell ruins my appetite so cooking isn't a problem.
Open hatches and fans help to move the noxious gas.

Ronbo
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Old 17-08-2009, 07:29   #8
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What Ronbo is smelling is Hydrogen Sulphide (H2S).
The odour of H2S is commonly mis-attributed to elemental sulfur, which is in fact odourless.
Hydrogen Sulphide (H2S) is the gas most commonly associated with the smell of sewage and rotten eggs; whereas Hydrogen gas is colourless and odourless.
The rotten egg odour is only detectable at very low concentrations. About half of the population can smell it at concentrations as low as 8 parts per billion (ppb) in air, and more than 90% can smell it at levels of 50 ppb. At higher concentrations, hydrogen sulfide rapidly deadens the sense of smell. For most people, this occurs at approximately 150 ppm (0.015% b.v.)

Further to my earlier post, here’s an excellent tutorial, explaining how to calculate battery ventilation requirements:
Calculate Industrial Battery Hydrogen Gas Emission - GB Industrial Battery
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Old 17-08-2009, 10:06   #9
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Sounds like a good reason to have an ignition-protected bilge blower even on a diesel boat, so it can help vent compartments while the batteries are being equalized.
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Old 17-08-2009, 10:33   #10
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Quote:
Originally Posted by hellosailor View Post
Sounds like a good reason to have an ignition-protected bilge blower even on a diesel boat...
Indeed!

As far as I know, American made fans, labelled as “Bilge Blowers”, are all ignition protected as required by USCG & UL specifications.

A Rough Guide to Sizing Bilge Blowers:
For engine spaces up to 70 cu. ft = 100 CFM blower
71 to 100 cu. ft. = 150 CFM blower
101 to 300 cu. ft. = 250 CFM blower

Note: Fans are rated on performance curves, with capacity (in CFM) declining from their highest (theoretical) capacity at “Open Flow”, down to lower capacities with increasing Static Pressures. Don’t use the open flow rating, which is unrealistically high in nearly all applications.

http://www.bronek.org/sailing/zamind...ttwood3000.pdf
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Old 17-08-2009, 19:43   #11
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Honestly Gord how do you know this stuff? Where do you come up with this info? I do have a bilge blower but as stated before, H rises so that won't help much. I do have some fans in the cabin and we usually live with all of the hatches open all the way 24/7. Do you guys think this will suffice?
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Old 17-08-2009, 20:46   #12
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Okay, let me throw some math at it. As I'm a metric guy, I'll uses inches and feet for fun, knowing I have some great backup here when I mess it up ;-)

One battery for one hour is 10-20 cubic centimeters. That's normally written as cm3 by the way, with the "3" as superscript which this editor doesn't allow me... Anyway, that's about the same as 1 cubic inch (1 cu.inch is 16.39cm3).

Now, let's say I have 6 batteries and equalize for 4 hours. That's 4 x 6 x 1 cu.inch = 24 cu.inch of hydrogen. A cubic foot has 1,728 cu.inches so it's 24/1728 = 1/72 cubic foot of hydrogen. This stuff explodes unless it's concentration is less than 4%. When we mix it with the other 71/72 of a cubic foot, it's concentration is... wel, 1/72 * 100% = 1.39%.

This would mean that it would be very hard to create an explosion by equalizing your batteries. So, who's gonna explain me where my math went way wrong because I can't really believe it myself. ;-)

cheers,
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Old 17-08-2009, 21:08   #13
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OK ...first off do not just set a timer and turn your charger on equalize for the specified time it lists or tells you to...that method can seriously dammage your batteries or indeed Cook them as has been worded here.

What you are trying to achieve is the maximum achievable specific gravity a battery can possibly get too...measured in each cell of each battery of IIRC of 14.2 specific gravity using a hydrometer...you know thoes squeeze bulbs with beads or a rotating pointer in them like an antifreeze tester. ( Gordy check me on that figure please will you...Thanks)

In other words this is a baby sitting job if done corectly and not an automatic one. You may indeed have to add some distilled water to a couple cells during the process as you check on them periodically , like every hour hence the need to have the caps off to monitor them.

Your charger is putting out roughly 15v during this process so they will get quite warm and boil off quite a bit of water.

Bottom line it could take 3 hours or the 8 your charger says it will but your not doing your batteries any good by forcing that charge into them any longer then absolutely necessary....besides with out the hydrometer you really dont know if the job got done at all.

And if they are all up but one cell well you know what that means...it aint going to come up and the battery is on its way down hill now fairly quickly.

Hope that helps.

OH I forgot the main question...Explosion.

I have exploded 2 batteries in my life so far..One went off like a cannon blast and through battrie acid all over the excavator the other one sounded more like a firecracker..both times we were jumping the batteries.

Its not the cabin filling full of gas but the concentrated gas in the battrie that will do the exploding..so its the spark hooking up or turning on a hooked up charger that in my cases created the source of ignition for the explosion.
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Old 17-08-2009, 22:12   #14
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Or use a Pulse-Tech battery conditioner (Whoo-boy! I can hear the screams already).
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Old 17-08-2009, 23:26   #15
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HA! Boy... I was so far off it is hilarious....but the rest is sound advice...Its 1.265 specific Gravity for 100 percent charge of a flooded battrie.


Hey its been a long time since High School...what can I say.....
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