[RE-wrenches] Battery based hydrogen incidents

R Ray Walters ray at solarray.com
Wed Dec 15 12:04:58 PST 2010


H2S is slightly heavier than air, but I vent with the inlets on line with the tops of the battery, and the outlet at the highest point.
If there is a lot of space around the bottom of the batteries, I might lower the inlets some, but not enough for the airflow to contribute to much cooling effect. (I'm in the Rockies)

All these stories make even more of a stickler about having my crews wear safety glasses.

R. Walters
ray at solarray.com
Solar Engineer




On Dec 15, 2010, at 12:08 PM, Jonathan Hill wrote:

> Ray-
> Is H2S lighter or heavier than air? Should it be vented from the top or bottom of the enclosure? Thanks.
> 
> Jonathan Hill, solar applications engineer
> Sierra Solar Systems
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> Grass Valley, CA 95945
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> On Dec 15, 2010, at 10:48 AM, R Ray Walters wrote:
> 
>> I really think the real venting issue is H2S (hydrogen sulfide) gas, which is deadly at high enough concentrations, causes head aches at lower concentrations, and is just awful to smell at any concentration.
>> I think you would have to literally design a battery box to explode to ever get to the 4% concentration necessary. It would consist of a large battery bank, ridiculously oversized charge source, 
>> the enclosure lid would be barely above the terminals, and the enclosure would be a refrigerator, or ice chest with excellent seals and gaskets all the way around.
>> Hydrogen is tough to contain, it can permeate right through many plastics, metals, sheetrock, etc.
>> Again despite article 480, the issue of venting is the H2S danger, and accelerated corrosion, not explosion.
>> I too, have had a hydrogen explosion, ( and cool colorless fire after!) but it wasn't due to the enclosure venting at all. (short circuited battery, lead terminal melted through battery case, ignition of hydrogen inside of battery, boom, then jet whistle sound of fire burning through the hole)
>> Article 480.9A should be revised from "explosive" mixture to "dangerous" mixture.  H2S above 10ppm?
>> I copied some toxicity info if anyone wants to see. 
>> 
>> R. Walters
>> ray at solarray.com
>> Solar Engineer
>> 
>> Long-term, low-level exposure may result in fatigue, loss of appetite, headaches, irritability, poor memory, and dizziness. Chronic exposure to low level H2S (around 2 ppm) has been implicated in increased miscarriage and reproductive health issues among Russian and Finnish wood pulp workers,[11] but the reports have not (as of circa 1995) been replicated.
>> 
>> 0.00047 ppm is the recognition threshold, the concentration at which 50% of humans can detect the characteristic odor of hydrogen sulfide,[12] normally described as resembling "a rotten egg".
>> Less than 10 ppm has an exposure limit of 8 hours per day.
>> 10–20 ppm is the borderline concentration for eye irritation.
>> 50–100 ppm leads to eye damage.
>> At 100–150 ppm the olfactory nerve is paralyzed after a few inhalations, and the sense of smell disappears, often together with awareness of danger.[13][14]
>> 320–530 ppm leads to pulmonary edema with the possibility of death.
>> 530–1000 ppm causes strong stimulation of the central nervous system and rapid breathing, leading to loss of breathing.
>> 800 ppm is the lethal concentration for 50% of humans for 5 minutes exposure (LC50).
>> Concentrations over 1000 ppm cause immediate collapse with loss of breathing, even after inhalation of a single breath.
>> 
>> 
>> 
>> On Dec 15, 2010, at 10:21 AM, Kent Osterberg wrote:
>> 
>>> Sounds like, in general, that the off-grid industry has been fortunate to not have hydrogen explosions.  That's good.  No explosions here either.  But one shouldn't take that as evidence that it couldn't happen.  I don't believe this is a circumstance where it is better to be lucky than good.  That's why I recommend doing the calculations.
>>> 
>>> Kent Osterberg
>>> Blue Mountain Solar
>>> 
>>> 
>>> 
>>> Dana wrote:
>>>> 
>>>> Ken –
>>>>  
>>>> To meet the flow have run 2 and 3 fans to meet the flow. 2” output from the fan into a 4” header with a matching 2.5” inlet as far away on the lowest portion of the battery box.
>>>>  
>>>>  
>>>> In 22+ years in off grid installations I have yet to see or even hear of one hydrogen explosion. I get repeatedly asked why we have to go to the efforts we go to for box and venting. I am not able to provide even one incident that I have heard rumor of.
>>>>  
>>>> Q - How many battery based hydrogen incidents have happened in our collective experience?
>>>>  
>>>>  
>>>>  
>>>> Dana Orzel
>>>> Great Solar Works, Inc
>>>> E - dana at solarwork.com
>>>> V - 970.626.5253
>>>> F - 970.626.4140
>>>> C - 970.209.4076
>>>> web - www.solarwork.com
>>>>  
>>>> "Responsible Technologies for Responsible People since 1988"
>>>> Do not ever belive anything, but seriously trust through action.
>>>>  
>>>> From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Kent Osterberg
>>>> Sent: Tuesday, December 14, 2010 12:07 PM
>>>> To: Wrenches
>>>> Subject: [RE-wrenches] Battery Venting
>>>>  
>>>> Fellow Wrenches,
>>>> 
>>>> The discussion about battery venting reminds me of a useful and inexpensive program, BattMV, for determining ventilation requirements per EN-50272.  EN-50272 is a European standard used to determine how much air flow is needed for a room, I don't know of a equivalent standard used in the U.S.  It takes a surprising amount of ventilation.  For a 400-AH 48-volt L16 bank charged at 57.6 volts and 24 amps, it's about 7 CFM just to keep the %H2 down to 4%.  A 12-volt Zephyr vent is good for about 5 CFM!   If you think you are venting enough, take some time and study this issue.
>>>> 
>>>> Kent Osterberg
>>>> Blue Mountain Solar
>>>> 
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