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John,<br>
<br>
Thanks for the follow-up on this subject. I'd like to change the
example to show the ventilation required rather than the hydrogen
liberated. <br>
<br>
Consider a 48-volt bank of L16RE-B batteries: that's 24 cells of 370
amphours. Using the 14 cc/hr/Ah/cell H2 rate for equalizing gives a
total hydrogen of 124320 cc/hr or 124.32 liter/hr. To keep the
hydrogen concentration down to 1% would require that the total
ventilation is is 12432 liter/hr or 12.432 cubic meters per hour or
7.3 CFM. A 12-volt Zephyr battery vent will move about 6 CFM, that
enough to keep the H2 concentration down to 1.2%. Zephyr Industries
claims the vent is suitable for 2200-amphour (12-volt) battery banks
which is six 370-amphour batteries. I've seen too many battery boxes
with no ventilation or with a single Zephyr vent for 16 or 24
batteries.<br>
<br>
There is a DIN standard (EN 50272) for ventilating battery rooms.
The calculations for it are based on an assumed (electrolyzing)
current for various charging voltages. The main reason it is
interesting is that the ventilation requirements come out about to
be twice as much as when using the H2 rates you provided. I suspect
that is partly because it is intended to to cover all batteries and
it is intentionally conservative.<br>
<pre class="moz-signature" cols="72">Kent Osterberg
Blue Mountain Solar, Inc.
<a class="moz-txt-link-abbreviated" href="http://www.bluemountainsolar.com">www.bluemountainsolar.com</a>
t: 541-568-4882</pre>
<br>
On 1/6/2012 5:53 PM, John DeBoever wrote:
<blockquote
cite="mid:CC4E5D1C542D8C4C9CBEE800875F05354776A7B8@Trojmail1.trojanbattery.com"
type="cite">
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<div class="WordSection1">
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Wrenches,<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Thank
you for your patience (as I was busy all day). I appreciate
the valid issues raised and good perspectives provided so
far by the Wrenches. I will try my best to clarify the
hydrogen production issues as follow. <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoListParagraph"
style="margin-left:.25in;text-indent:-.25in;mso-list:l1 level1
lfo3">
<!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:Symbol;color:#1F497D"><span
style="mso-list:Ignore">·<span style="font:7.0pt
"Times New Roman"">
</span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">All
lead acid batteries, flooded and VRLA require ventilation.
Flooded lead acid generate much more hydrogen by design and
require watering maintenance. VRLA AGM, per design, have up
to 99% hydrogen recombination, so production of hydrogen is
much smaller, yet still release hydrogen and require
ventilation to keep the hydrogen content between 1% to 2%.
Sealed enclosure is no go in term of safety, as 4% hydrogen
content is highly explosive.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p></o:p></span></p>
<p class="MsoListParagraph"
style="margin-left:.25in;text-indent:-.25in;mso-list:l3 level1
lfo2">
<!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:Symbol;color:#1F497D"><span
style="mso-list:Ignore">·<span style="font:7.0pt
"Times New Roman"">
</span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Here
are the (approximation) ranges for Hydrogen gassing rates of
Trojan deep-cycle flooded batteries for:
<o:p></o:p></span></p>
<p class="MsoNormal"
style="margin-left:.5in;text-indent:-.25in;mso-list:l2 level1
lfo1">
<!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:Wingdings;color:#1F497D"><span
style="mso-list:Ignore">ü<span style="font:7.0pt
"Times New Roman"">
</span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Float
Charging (2.20 VPC @ 25<sup>o</sup>C)
1.0 to
<b>2.5 </b>cc/hr/Ah/cell<o:p></o:p></span></p>
<p class="MsoNormal"
style="margin-left:.5in;text-indent:-.25in;mso-list:l2 level1
lfo1">
<!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:Wingdings;color:#1F497D"><span
style="mso-list:Ignore">ü<span style="font:7.0pt
"Times New Roman"">
</span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Absorption
Charging (2,47VPC @ 25<sup>o</sup>C) 2.5 to
<b>4.5</b> cc/hr/Ah/cell<o:p></o:p></span></p>
<p class="MsoNormal"
style="margin-left:.5in;text-indent:-.25in;mso-list:l2 level1
lfo1">
<!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:Wingdings;color:#1F497D"><span
style="mso-list:Ignore">ü<span style="font:7.0pt
"Times New Roman"">
</span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Equalize
Charging (2.58VPC @ 25<sup>o</sup>C) 4.5 to
<b>14.0</b> cc/hr/Ah/cell <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Please
be advised that a range is given since Hydrogen production
vary with the battery voltage during the said charge mode
duration, quality of charge algorithm to tapper the current
vs. voltage and total duration, and, vary over the life of
the battery, ageing of the battery and application
specifics. To be on safe side, I recommend to consider the
<b>higher</b> approximate figure for conservative Hydrogen
production value. Please note these are given at 77F (25C).
Higher temperature will generate higher current levels and
hopefully a temperature compensation feature of the voltage
settings will take place to mitigate the impact. <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Example:
Trojan Signature T-105: 225 Ah @ 6V @ C/20: 225 Ah x 3 cells
x 4.5 cc/hr/Ah/cell = 3,040 cc/hr during the absorption
charge, @ 25C. During equalization @ 25C, production of
hydrogen is intense: 225 x 3 x 14 = 9,450 cc/hr. Use these
values as inputs for further calculations for ventilation
requirements per applicable standards.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoListParagraph"
style="margin-left:.25in;text-indent:-.25in;mso-list:l3 level1
lfo2">
<!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:Symbol;color:#1F497D"><span
style="mso-list:Ignore">·<span style="font:7.0pt
"Times New Roman"">
</span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The
“float charging” mentioned above is kind of confusing to
many. Indeed, there should be no mention of gassing during
“float” charge mode, since we are below gassing voltage. It
is mentioned for info here although not typical for
deep-cycle products: the Hydrogen production is only a
concern for UPS type of applications, where the battery
stays at float charge for several days /months. Float charge
mode is actually meant in “float” applications to mitigate
the self-discharge of the battery due to its natural
self-discharge. Indeed, even the very small float charge
current build up hydrogen over time. Note: VRLA technology
will generate less Hydrogen than flooded since the required
float current will be less for VRLA technology (0.2 to 0.5%
of C/20). Sorry for the confusion to cyclic applications
minded Wrenches.<o:p></o:p></span></p>
<p class="MsoListParagraph" style="margin-left:.25in"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoListParagraph"
style="margin-left:.25in;text-indent:-.25in;mso-list:l3 level1
lfo2">
<!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:Symbol;color:#1F497D"><span
style="mso-list:Ignore">·<span style="font:7.0pt
"Times New Roman"">
</span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Here
are the (approximation) range for Hydrogen gassing rates of
Trojan VRLA AGM batteries for:<o:p></o:p></span></p>
<p class="MsoListParagraph"
style="text-indent:-.25in;mso-list:l0 level1 lfo4"><!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:Wingdings;color:#1F497D"><span
style="mso-list:Ignore">ü<span style="font:7.0pt
"Times New Roman"">
</span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Float
Charging (2.25 VPC @25<sup>o</sup>C)
0.01 to 0.019 cc/hr/Ah/cell<o:p></o:p></span></p>
<p class="MsoListParagraph"
style="text-indent:-.25in;mso-list:l0 level1 lfo4"><!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:Wingdings;color:#1F497D"><span
style="mso-list:Ignore">ü<span style="font:7.0pt
"Times New Roman"">
</span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Absorption
Charging (2.45VPC@ 25<sup>o</sup>C) 0.019 to
0.025 cc/hr/Ah/cell<o:p></o:p></span></p>
<p class="MsoListParagraph"
style="text-indent:-.25in;mso-list:l0 level1 lfo4"><!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:Wingdings;color:#1F497D"><span
style="mso-list:Ignore">ü<span style="font:7.0pt
"Times New Roman"">
</span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Boost
Charging (2.39 VPC @25<sup>o</sup>C)
0.013 to 0.015 cc/hr/Ah/cell
<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Please
be advised the “boost” charging is only acceptable on VRLA
AGM, not VRLA GEL. It has the same role as the regular
equalization event: to equalize the cells, although for a
much lower voltage and very limited time. The “boost”
charging is often not activated as a safety precaution on
poor charge algorithms.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Please
keep in mind that the above are approximations, as, when
lead acid batteries issues are involved, “it depends” is the
first words you hear from battery OEM’s. Hope this is
helps.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Good
evening,<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">John<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<br>
</div>
</blockquote>
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