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<DIV><FONT size=2 face=Calibri>That is a problem with a single string,
yes.</FONT></DIV>
<DIV><FONT size=2 face=Calibri></FONT> </DIV>
<DIV><FONT size=2 face=Calibri>The biggest problem I have seen with large banks
is what you describe with the cross connections - either not enough or too small
of wire.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2
face=Arial>..................................................................................................<BR>Northern
Arizona Wind & Sun - Electricity From The Sun Since 1979<BR>Solar Discussion
Forum: <A
href="http://www.wind-sun.com/ForumVB/">http://www.wind-sun.com/ForumVB/</A><BR>..................................................................................................</FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=ray@solarray.com href="mailto:ray@solarray.com">R Ray Walters</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=re-wrenches@lists.re-wrenches.org
href="mailto:re-wrenches@lists.re-wrenches.org">RE-wrenches</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, December 01, 2009 11:43
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [RE-wrenches] concord
batteries, EQUALIZE Them!</DIV>
<DIV><BR></DIV><BR>
<DIV><SPAN
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class=Apple-style-span>
<DIV>I used to think that one string was optimal; until I had a single cell
failure take out an entire system for weeks. (try operating a 24 v system at
22v! )</DIV>
<DIV>I now think that 2 parallel strings is optimum, 3 is OK, and 4 is
max.</DIV>
<DIV><SPAN style="FONT-SIZE: medium" class=Apple-style-span>At 4 parallel
strings, we start spending more time looking to make sure all connectors are
the same exact length etc. to insure equal
operation.</SPAN></DIV></SPAN></DIV>
<DIV>But of course how do you account for varying internal resistance of the
batteries......??</DIV>
<DIV>I've done 4 parallel strings at 144 DC of sealed batteries on an electric
vehicle, but we were very careful with our resistances, I even switched to
smaller wire, on closer strings, and calculated out the exact resistance, so
all strings were theoretically equal. This set actually just died, but
achieved its manufacturer's predicted cycle life. (B&B battery, 350 cycles
to 80% DOD)</DIV>
<DIV>So if you're careful, 4 strings can work well.</DIV>
<DIV>Worst I've seen was 20 golf carts paralleled in a 12 v system, (10
strings) and they didn't pull the main connections from across the set, just
connected to one end.</DIV>
<DIV>The results were very predictable, with the furthest batteries being
chronically under charged, and the closest ones being over cycled to a
premature death.</DIV>
<DIV><BR></DIV>
<DIV>Ray Walters</DIV>
<DIV><BR></DIV><BR>
<DIV>
<DIV>On Dec 1, 2009, at 11:28 AM, <A
href="mailto:Windsun@wind-sun.com">Windsun@wind-sun.com</A> wrote:</DIV><BR
class=Apple-interchange-newline>
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<DIV><FONT size=2 face=Calibri>You gotta wonder about why the customer
bought such a battery layout, or why the installer sold that kind of
configuration (which ever it was) with so many small batteries. We
would never recommend going over 2 parallel banks, but sometimes the
"customer knows best...".</FONT></DIV>
<DIV><FONT size=2
face=Calibri></FONT> </DIV></DIV></BLOCKQUOTE></DIV><BR>
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