<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">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.<div>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, </div><div>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.</div><div>Hydrogen is tough to contain, it can permeate right through many plastics, metals, sheetrock, etc.</div><div>Again despite article 480, the issue of venting is the H2S danger, and accelerated corrosion, not explosion.</div><div>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)</div><div>Article 480.9A should be revised from "explosive" mixture to "dangerous" mixture. H2S above 10ppm?</div><div>I copied some toxicity info if anyone wants to see. </div><div><br><div>
<span class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: auto; -khtml-text-decorations-in-effect: none; text-indent: 0px; -apple-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><div>R. Walters</div><div><a href="mailto:ray@solarray.com">ray@solarray.com</a></div><div>Solar Engineer</div><div><br class="khtml-block-placeholder"></div><div><p>Long-term, low-level exposure may result in <a href="http://en.wikipedia.org/wiki/Fatigue_%28physical%29" title="Fatigue (physical)" class="mw-redirect">fatigue</a>, loss of appetite, <a href="http://en.wikipedia.org/wiki/Headach" title="Headach" class="mw-redirect">headaches</a>, irritability, poor memory, and <a href="http://en.wikipedia.org/wiki/Dizziness" title="Dizziness">dizziness</a>. Chronic exposure to low level H<sub>2</sub>S (around 2 <a href="http://en.wikipedia.org/wiki/Parts_per_million" title="Parts per million" class="mw-redirect">ppm</a>) has been implicated in increased miscarriage and reproductive health issues among Russian and Finnish wood pulp workers,<sup id="cite_ref-10" class="reference"><a href="http://en.wikipedia.org/wiki/Hydrogen_sulfide#cite_note-10"><span>[</span>11<span>]</span></a></sup> but the reports have not (as of circa 1995) been replicated.</p>
<ul>
<li>0.00047 <a href="http://en.wikipedia.org/wiki/Parts_per_million" title="Parts per million" class="mw-redirect">ppm</a> is the recognition threshold, the concentration at which 50% of humans can detect the characteristic odor of hydrogen sulfide,<sup id="cite_ref-11" class="reference"><a href="http://en.wikipedia.org/wiki/Hydrogen_sulfide#cite_note-11"><span>[</span>12<span>]</span></a></sup> normally described as resembling "a rotten egg".</li>
<li>Less than 10 ppm has an exposure limit of 8 hours per day.</li>
<li>10–20 ppm is the borderline concentration for eye irritation.</li>
<li>50–100 ppm leads to eye damage.</li>
<li>At 100–150 ppm the <a href="http://en.wikipedia.org/wiki/Olfactory_nerve" title="Olfactory nerve">olfactory nerve</a> is paralyzed after a few inhalations, and the sense of smell disappears, often together with awareness of danger.<sup id="cite_ref-12" class="reference"><a href="http://en.wikipedia.org/wiki/Hydrogen_sulfide#cite_note-12"><span>[</span>13<span>]</span></a></sup><sup id="cite_ref-13" class="reference"><a href="http://en.wikipedia.org/wiki/Hydrogen_sulfide#cite_note-13"><span>[</span>14<span>]</span></a></sup></li>
<li>320–530 ppm leads to <a href="http://en.wikipedia.org/wiki/Pulmonary_edema" title="Pulmonary edema">pulmonary edema</a> with the possibility of death.</li>
<li>530–1000 ppm causes strong stimulation of the <a href="http://en.wikipedia.org/wiki/Central_nervous_system" title="Central nervous system">central nervous system</a> and rapid breathing, leading to loss of breathing.</li>
<li>800 ppm is the lethal concentration for 50% of humans for 5 minutes exposure (<a href="http://en.wikipedia.org/wiki/LC50" title="LC50" class="mw-redirect">LC50</a>).</li>
<li>Concentrations over 1000 ppm cause immediate collapse with loss of breathing, even after inhalation of a single breath.</li>
</ul><div><br></div></div><br class="Apple-interchange-newline"></span>
</div>
<br><div><div>On Dec 15, 2010, at 10:21 AM, Kent Osterberg wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">
<div bgcolor="#ffffff" text="#000000">
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.<br>
<br>
Kent Osterberg<br>
Blue Mountain Solar<br>
<br>
<br>
<br>
Dana wrote:
<blockquote cite="mid:003601cb9c72$8db6bfc0$a9243f40$@com" type="cite">
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<div class="WordSection1"><p class="MsoNormal"><span style="font-size: 14pt; font-family: "Century Gothic","sans-serif"; color: windowtext;">Ken
– <o:p></o:p></span></p><p class="MsoNormal"><span style="font-size: 14pt; font-family: "Century Gothic","sans-serif"; color: windowtext;"><o:p> </o:p></span></p><p class="MsoNormal"><span style="font-size: 14pt; font-family: "Century Gothic","sans-serif"; color: windowtext;">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.<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size: 14pt; font-family: "Century Gothic","sans-serif"; color: windowtext;"><o:p> </o:p></span></p><p class="MsoNormal"><span style="font-size: 14pt; font-family: "Century Gothic","sans-serif"; color: windowtext;"><o:p> </o:p></span></p><p class="MsoNormal"><span style="font-size: 14pt; font-family: "Century Gothic","sans-serif"; color: windowtext;">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.<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size: 14pt; font-family: "Century Gothic","sans-serif"; color: windowtext;"><o:p> </o:p></span></p><p class="MsoNormal"><span style="font-size: 14pt; font-family: "Century Gothic","sans-serif"; color: windowtext;">Q
- How many battery based hydrogen incidents have happened in our
collective experience?<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size: 14pt; font-family: "Century Gothic","sans-serif"; color: windowtext;"><o:p> </o:p></span></p><p class="MsoNormal"><span style="font-size: 14pt; font-family: "Century Gothic","sans-serif"; color: windowtext;"><o:p> </o:p></span></p><p class="MsoNormal"><span style="font-size: 14pt; font-family: "Century Gothic","sans-serif"; color: windowtext;"><o:p> </o:p></span></p>
<div><p class="MsoNormal"><span style="font-family: "Century Gothic","sans-serif"; color: windowtext;">Dana
Orzel<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family: "Century Gothic","sans-serif"; color: windowtext;">Great
Solar Works, Inc<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family: "Century Gothic","sans-serif"; color: windowtext;">E
- <a class="moz-txt-link-abbreviated" href="mailto:dana@solarwork.com">dana@solarwork.com</a><o:p></o:p></span></p><p class="MsoNormal"><span style="font-family: "Century Gothic","sans-serif"; color: windowtext;">V
- 970.626.5253<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family: "Century Gothic","sans-serif"; color: windowtext;">F
- 970.626.4140<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family: "Century Gothic","sans-serif"; color: windowtext;">C
- 970.209.4076<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family: "Century Gothic","sans-serif"; color: windowtext;">web
- <a class="moz-txt-link-abbreviated" href="http://www.solarwork.com/">www.solarwork.com</a><o:p></o:p></span></p><p class="MsoNormal"><span style="font-family: "Century Gothic","sans-serif"; color: windowtext;"><o:p> </o:p></span></p><p class="MsoNormal"><span style="font-family: "Century Gothic","sans-serif"; color: windowtext;">"Responsible
Technologies for Responsible People since 1988"</span><span style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: windowtext;"><o:p></o:p></span></p><p class="MsoNormal"><span style="font-family: "Century Gothic","sans-serif"; color: windowtext;">Do
not ever belive anything, but seriously trust through action.<o:p></o:p></span></p>
</div><p class="MsoNormal"><span style="font-size: 14pt; font-family: "Century Gothic","sans-serif"; color: windowtext;"><o:p> </o:p></span></p>
<div>
<div style="border-style: solid none none; border-color: rgb(181, 196, 223) -moz-use-text-color -moz-use-text-color; border-width: 1pt medium medium; padding: 3pt 0in 0in;"><p class="MsoNormal" style="margin-left: 0.5in;"><b><span style="font-size: 10pt; font-family: "Tahoma","sans-serif"; color: windowtext;">From:</span></b><span style="font-size: 10pt; font-family: "Tahoma","sans-serif"; color: windowtext;">
<a class="moz-txt-link-abbreviated" href="mailto:re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a>
[<a class="moz-txt-link-freetext" href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>] <b>On Behalf Of </b>Kent
Osterberg<br>
<b>Sent:</b> Tuesday, December 14, 2010 12:07 PM<br>
<b>To:</b> Wrenches<br>
<b>Subject:</b> [RE-wrenches] Battery Venting<o:p></o:p></span></p>
</div>
</div><p class="MsoNormal" style="margin-left: 0.5in;"><o:p> </o:p></p><p class="MsoNormal" style="margin-left: 0.5in;">Fellow Wrenches,<br>
<br>
The discussion about battery venting reminds me of a useful and
inexpensive program, <a moz-do-not-send="true" href="http://pocketengineer.design.officelive.com/battery_ventilation.aspx">BattMV</a>,
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.<br>
<br>
Kent Osterberg<br>
Blue Mountain Solar<o:p></o:p></p>
</div>
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