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Maybe i'm just lucky but my wife and I have been living off grid for several years now with two battery banks.<br><br>The first bank we bought new 5 years ago, which are 16 Rolls S530's. The second are 16 Rolls S460's that we inherited from a customer that was sick of his battery back up system and SW inverter. The S460's are now 7 years old. <br>I added the second bank for lack of a better use for used batteries.<br>I put them on a switch so that when one bank gets drawn down to just below 50% we switch to the other bank. <br><br>The bank that's not in use has a small array and CC (which is also switched) to keep it charged. <br><br>We have had no power problems and both banks continue to operate as would be expected from a new bank. <br><br>I equalize the batteries via the 7KW PV array every month (when possible) and add water every four mo's or so. <br><br>I'm not sure if all of the sudden the banks are going to take a performance nose dive but they are holding up fine for now. <br><br>It's my opinion (and we do this for all of our battery system customers) that the Key is to set the cut-off point just below 50% and provide the customer with a battery monitoring device <b>in their home</b>. <br>We tell our customers "When its cloudy cut back on your energy consumption or else your system will shut down before killing your batteries".<br><br>Just my $.02<br><br><font style="" color="#76923c">Wayne Irwin EE</font><font style="" color="#76923c"><br></font><font style="" color="#76923c">
Pure Energy Solar International Inc. </font><font style="" color="#76923c"><br></font><font style="" color="#76923c"></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 href="mailto:PureEnergySolar@hotmail.com">Wayne@PureEnergySolar.com</a> <br>
<a href="http://pureenergysolar.net">http://pureenergysolar.com</a> <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><br><p class="EC_EC_EC_EC_EC_MsoNormal"><font style="" color="#76923c"><span style="font-size: 10pt; font-family: 'Arial','sans-serif';">The
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<p class="EC_EC_EC_EC_EC_MsoNormal"><span style="font-family: 'Arial','sans-serif';"> <br></span></p><br><br><br><br><br><hr id="stopSpelling">From: tcreswell@ozarkenergyservices.com<br>To: re-wrenches@lists.re-wrenches.org<br>Date: Tue, 1 Dec 2009 16:15:53 -0600<br>Subject: Re: [RE-wrenches] Other's thoughts on Autonomy? was concord batteries, EQUALIZE Them!<br><br>
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<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;">IMHO, one of the worst design
boo-boo’s is going past more then 2 days of autonomy. Personally, I
no longer size much over one day because it’s my anecdotal observation
that most batteries die of old age and being ignored long before cycles get
them. Speaking mostly about quality deep cycle flooded.</span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;">Lots of good things result;</span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;">-50%-75% smaller battery bank means a $20,000
battery bank just turned into $5,000 bank which frees up a ton of money for
more modules and now-a-days you can buy a lot more PV with that money. More
array mean far less reliance on autonomy. I’ll take the trade all
year long. In the summer we have 3 to 4 weeks of sun and one day of
clouds and in the winter we get 3 to 4 week stretches with 1 sunny day. Autonomy
doesn’t really matter in either case from what I’ve seen. The
larger the bank means more self discharge losses, which on large battery banks
gets significant as they age. 5-15 years later you’ll still have all
that array but no matter what you’re looking at new battery bank.</span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;">-If you study the quality deep cycle
manufacturers literature you’ll see that you’ll see that anything
over 1 day of autonomy is too much to allow the array to actually charge the
battery bank anywhere near the recommended amps and just like rust, sulfation never
sleeps.</span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;">-Less cells to water</span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;">-Less space required</span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;">-Given that a surprisingly high percentage
of off gridders totally screw up on their first bank, no matter how much we all
try we might as keep the stupid tax of replacing a 2.5 yr old battery bank to a
minimum.</span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;">-All of this discussion about cross paralleling,
buss bars, TLC with a gazillion connections and multiple strings goes away.</span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;">-And the best part is we don’t have
to carry all of the lead into the basement and even better back out of the
basement!</span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;">Just my .02. Feel free to strongly
disagree but let’s be polite about it.</span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;">Travis Creswell</span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;">Ozark Energy Services</span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font></p>
<p class="ecxMsoNormal"><font color="navy" face="Arial" size="2"><span style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font></p>
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<p class="ecxMsoNormal"><b><font face="Tahoma" size="2"><span style="font-size: 10pt; font-family: Tahoma; font-weight: bold;">From:</span></font></b><font face="Tahoma" size="2"><span style="font-size: 10pt; font-family: Tahoma;">
re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b><span style="font-weight: bold;">On Behalf Of </span></b>R Ray Walters<br>
<b><span style="font-weight: bold;">Sent:</span></b> Tuesday, December 01, 2009
12:44 PM<br>
<b><span style="font-weight: bold;">To:</span></b> RE-wrenches<br>
<b><span style="font-weight: bold;">Subject:</span></b> Re: [RE-wrenches] concord
batteries, EQUALIZE Them!</span></font></p>
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<p class="ecxMsoNormal"><font face="Times New Roman" size="3"><span style="font-size: 12pt;"> </span></font></p>
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<p class="ecxMsoNormal"><font color="black" face="Helvetica" size="5"><span style="font-size: 16pt; font-family: Helvetica; color: black;">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! )</span></font></p>
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<p class="ecxMsoNormal"><font color="black" face="Helvetica" size="5"><span style="font-size: 16pt; font-family: Helvetica; color: black;">I now think that 2
parallel strings is optimum, 3 is OK, and 4 is max.</span></font></p>
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<p class="ecxMsoNormal"><span class="ecxapple-style-span"><font color="black" face="Helvetica" size="4"><span style="font-size: 13.5pt; font-family: Helvetica; color: black;">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></font></span><font color="black" face="Helvetica" size="5"><span style="font-size: 16pt; font-family: Helvetica; color: black;"></span></font></p>
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<p class="ecxMsoNormal"><font face="Times New Roman" size="3"><span style="font-size: 12pt;"></span>But of course how do you account for varying internal resistance
of the batteries......??</font></p>
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<p class="ecxMsoNormal"><font face="Times New Roman" size="3"><span style="font-size: 12pt;">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)</span></font></p>
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<p class="ecxMsoNormal"><font face="Times New Roman" size="3"><span style="font-size: 12pt;">So if you're careful, 4 strings can work well.</span></font></p>
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<p class="ecxMsoNormal"><font face="Times New Roman" size="3"><span style="font-size: 12pt;">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.</span></font></p>
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<p class="ecxMsoNormal"><font face="Times New Roman" size="3"><span style="font-size: 12pt;">The results were very predictable, with the furthest batteries being
chronically under charged, and the closest ones being over cycled to a
premature death.</span></font></p>
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<p class="ecxMsoNormal"><font face="Times New Roman" size="3"><span style="font-size: 12pt;">Ray Walters</span></font></p>
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<p class="ecxMsoNormal"><font face="Times New Roman" size="3"><span style="font-size: 12pt;">On Dec 1, 2009, at 11:28 AM, <a href="mailto:Windsun@wind-sun.com">Windsun@wind-sun.com</a>
wrote:</span></font></p>
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<p class="ecxMsoNormal"><font face="Calibri" size="2"><span style="font-size: 10pt; font-family: 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...".</span></font></p>
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