<html><body><div style="color:#000; background-color:#fff; font-family:arial, helvetica, sans-serif;font-size:12pt"><div id="yiv81996976"><div style="color:#000;background-color:#fff;font-family:arial, helvetica, sans-serif;font-size:12pt;"><div id="yiv81996976yui_3_2_0_3_130688310795348"><span id="yiv81996976yui_3_2_0_3_130688310795399">If one cell gets a higher internal loss than the others is hogs the charging current and will over charge its string partners. It is a problem of the temperature of all cells in all parallel strings having the same thermal environment, so they all have the same voltage. (the case of one of 4 parallel strings in battery house, big system, the string near the outside south wall caught fire) In particular this is a problem of AGMs, a recent east cost problem where batteries had been in business for 2 yrs and for some reason the battery room erupted with one of 5 strings in thermal runaway. this is
the same as trying to put bipolar transistors in parallel. <br><br>I reciently had 8 parallel strings not of my choice, advised customer of potential hazard, used Midnight combiner with 30 amp breakers on each string, so far it is OK but this is playing with fire. Hopfully if one string goes bad in thermal runaway it will trip the breaker feeding that string. . <br></span><span></span></div><div id="yiv81996976yui_3_2_0_3_1306883107953120"><br id="yiv81996976yui_3_2_0_3_130688310795351"></div><div class="yiv81996976yui_3_2_0_3_130688310795352" id="yiv81996976yui_3_2_0_3_130688310795354" style="font-family:arial, helvetica, sans-serif;font-size:12pt;"><div class="yiv81996976yui_3_2_0_3_130688310795357" style="font-family:times new roman, new york, times, serif;font-size:12pt;"><font face="Arial" size="2"><hr size="1"><b><span style="font-weight:bold;">From:</span></b> boB Gudgel <boB@midnitesolar.com><br><b><span
style="font-weight:bold;">To:</span></b> RE-wrenches <re-wrenches@lists.re-wrenches.org><br><b><span style="font-weight:bold;">Sent:</span></b> Wednesday, June 1, 2011 1:16 AM<br><b><span style="font-weight:bold;">Subject:</span></b> Re: [RE-wrenches] 24 volt Battery Bank comparison<br></font><br>
<div id="yiv81996976">
<br>
<br>
OK, I've been hearing for years now that one battery string is best
and maybe two but no more should be used.<br>
<br>
What is the reason for this fear ??? What is the experience with
multiple strings in parallel ??<br>
<br>
If it is because of current sharing of the strings, that shouldn't
be an insurmountable problem if the wiring is done right.<br>
<br>
If it has to do with the possibility of fire, which Darryl
mentioned, seems that series string fuses could mitigate the
possibility of that issue, if because of shorted cells, just like PV
combiners.<br>
<br>
Or maybe it has to do with the trouble of getting into the middle of
a pile of batteries ? Use battery boxes ?<br>
<br>
The strings are in parallel and so they all get the same voltage,
theoretically anyway if the connections are good.<br>
<br>
I would think that the more strings, the LESS stress on individual
batteries, not more. The current in each battery should be less
than it would be I would think.<br>
<br>
So what is the real experience ?? <br>
<br>
Is a battery balancer the answer ??<br>
<br>
Thanks,<br>
boB<br>
<br>
<br>
<br>
<br>
<br>
<blockquote type="cite">
<div><br>
On May 31, 2011, at 8:23 PM, "Wayne Irwin" <<a rel="nofollow" ymailto="mailto:wayne@pureenergysolar.com" target="_blank" href="mailto:wayne@pureenergysolar.com">wayne@pureenergysolar.com</a>>
wrote:<br>
<br>
</div>
<blockquote type="cite">
<div>
I think the verdict is<b> 12</b> - Rolls 2-YS-31 2430 AH @ 20
HR (one string) and one dry spare in storage is the best case
scenario!<br>
<br>
<font style="" color="#76923c">Wayne Irwin</font><font style="" color="#76923c">, EE<br>
Director of Engineering<br>
</font><font style="" color="#76923c">
Pure Energy Solar International Inc. </font><font style="" color="#76923c"><br>
</font><font style="" color="#76923c">State Licensed Solar
Contractor</font><font style="" color="#76923c"><br>
</font><font style="" color="#76923c">
License # CVC56695 </font><br>
<a rel="nofollow" ymailto="mailto:Wayne@PureEnergySolar.com" target="_blank" href="mailto:Wayne@PureEnergySolar.com">Wayne@PureEnergySolar.com</a>
<br>
http://pureenergysolar.com
<br>
<font style="" color="#76923c">352 377-6527 Office</font><font style="" color="#76923c"><br>
</font><font style="" color="#76923c">352 336-3299 Fax</font><font style="" color="#76923c"><br>
</font><font style="" color="#76923c">352 316-1637 Cell</font></div>
</blockquote>
</blockquote>
<br>
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