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<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Century Gothic","sans-serif"'>What
do specific gravity and load, rest and charge VPC tests say? <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Century Gothic","sans-serif"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Century Gothic","sans-serif"'>The
VPC tests will usually pinpoint a weak cell. <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Century Gothic","sans-serif"'>Higher
VPC reading under a high state of charge and lower VPC under a big load,
normally done with the array & generator turned off to maximize the effect.
<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Century Gothic","sans-serif"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Century Gothic","sans-serif"'>Typically
the specific gravity reading will confirm this VPC test cell readings and the
SG will be lower for that cell too.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Century Gothic","sans-serif"'><o:p> </o:p></span></p>
<div>
<p class=MsoNormal><span style='font-family:"Century Gothic","sans-serif"'>Thanks,
Dana Orzel<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Century Gothic","sans-serif"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-family:"Century Gothic","sans-serif"'>Great
Solar Works, Inc<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Century Gothic","sans-serif"'>E -
dana@solarwork.com<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Century Gothic","sans-serif"'>V -
970.626.5253<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Century Gothic","sans-serif"'>F -
970.626.4140<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Century Gothic","sans-serif"'>C -
970.209.4076<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Century Gothic","sans-serif"'>web
- www.solarwork.com<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Century Gothic","sans-serif"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-family:"Century Gothic","sans-serif"'>"Responsible
Technologies for Responsible People since 1988"</span><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif"'><o:p></o:p></span></p>
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<p class=MsoNormal style='margin-left:.5in'><b><span style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>Mark
Frye<br>
<b>Sent:</b> Thursday, July 22, 2010 11:30 AM<br>
<b>To:</b> 'RE-wrenches'<br>
<b>Subject:</b> [RE-wrenches] Imbalance In Multiple String Charging Current<o:p></o:p></span></p>
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<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p style='margin-left:.5in'><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Folks,</span>
<o:p></o:p></p>
<p style='margin-left:.5in'><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>I
have three strings of batteries cabled in parallel to a common buss bar.</span>
<o:p></o:p></p>
<p style='margin-left:.5in'><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>During
charging, one string takes significantly less current than the others.</span> <o:p></o:p></p>
<p style='margin-left:.5in'><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>What
can I infer from this? Is the low current string healthier, presenting higher
impedance due to a higher state of charge? Or is there a single bad cell with
high impedance in this string? Both, neither, something else, or can't know
without further information?</span><o:p></o:p></p>
<p style='margin-left:.5in'><span style='font-family:"Arial","sans-serif"'> </span>
<br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Mark Frye</span>
<br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Berkeley Solar
Electric Systems</span> <br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>303 Redbud Way</span>
<br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Nevada
City, CA 95959</span> <br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>(530) 401-8024</span>
<br>
<a href="http://www.berkeleysolar.com"><span style='font-size:10.0pt;
font-family:"Arial","sans-serif"'>www.berkeleysolar.com</span></a><span
style='font-size:10.0pt;font-family:"Arial","sans-serif"'> </span> <o:p></o:p></p>
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