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Author Topic: battery gas saftey ?  (Read 3683 times)
dodgy rog
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« on: November 08, 2008, 07:48:14 PM »

hello i understand that lead acid batterys give of gas when being charged especialy when eqalized, my question is if i mount my forklift battery bank directly below all other controll gear including inv/charger and trip switches does this creat a risk of explosion? all hardware will be in a box say 1.2Metres wide .750 m deep and 2metres tall vented top and bottom situated outside but weather proof. any advice welcolme
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guydewdney
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« Reply #1 on: November 08, 2008, 07:53:11 PM »

from my horsebox / campervan knowledge - you need to vent to outside in a 'drop hole' - which I never quite understand, as hydrogen gas rises.

as long as its not in a nice sealed box, with decent airflow - it will be fine. Insulate the battery box - as cold kills batterys for some reason.
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Bob
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« Reply #2 on: November 10, 2008, 06:58:39 AM »

It is not just H2 that is given off by batteries when they are being charged.  I have a tin roof on my shed abd immediately above where I used to have the batteries is a large patch of gray corrosion on the zinc of the corrugated iron.  I have not analyzed it but it does look like zinc sulfate.

My guess is that there is a small but significant amount of S02 or So3 being given off as well.  Not good for the electrics!

Best practice is to connect the vent points together with plastic waste pipe and vent to the outside.

Not sure that I agree with Guy's (Hi Guy) drop hole.

Bob
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martin
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« Reply #3 on: November 10, 2008, 10:05:50 AM »

I've got a feeling that the "drop hole" is more to vent propane/butane from the gas bottles commonly used in vehicles of that sort. When I spent time around boats, it was common practice to bung the gas bottles in a compartment on deck positioned next to the scuppers with good "drainage" at the base as the gases are heavier than air, and were the cause of many explosions when hulls filled with the stuff, and then people lit a ciggy, or pressed the starter! Wink
I'd go with the "pipe them together and vent outside" advice
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Eleanor
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« Reply #4 on: November 10, 2008, 10:36:29 AM »

Bob, good to see you back Cheesy
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oliver90owner
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« Reply #5 on: November 14, 2008, 08:09:46 PM »

Hydrogen gas not only rises but is so energetic (well highest velocity for a given energy level (temperature) of any gas ) will go any which way.  It will soon disperse given any outlet.  I would always say a hole at the bottom and a short down-turned vent at the top, to allow free air movement without water ingress for maximum safety.  Less venting for thermal efficiency!!

An equalisation charge (or any gassing cells) are an explosion hazard - it is not only the hydrogen, but also the stoichemetric quantity of oxygen which is involved (electrolysis of water).  Until the hydrogen diffuses away there is the perfect ratio of oxygen to hydrogen (with little nitrogen to dilute it) for the maximum explosive effect for that small amount of gas, especially that which is still inside the cells.

The acidic corrosion is probably simply due to the 'fizzing' of the equalisation gassing causing an aerosol effect and a little of this mist rising with the warm air stream to the roof (the cells will heat quite quickly when they are gassing, as the electrolysis of water has its own 'efficiency of reaction').  But there again gassing cells do have a characteristic smell and neither hydrogen or oxygen smell...

Regards, RAB
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northern installer
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« Reply #6 on: November 14, 2008, 09:44:32 PM »

I think the 'acid smell' from gassing batteries comes from acid mist or vapour carried over by the released gasses;in any case ,it is quite destructive if allowed to linger,so I would always advocate a low level of forced ventilation in a battery room,being careful where you discharge it;after all,do we really know what health problems are caused by 'battery vapour'?
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