<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>David, </div><div>Windy's system sizing spreadsheet was first developed in the 1990s or so, when PV was expensive and lead (and copper) were relatively cheap. In those days, "one panel per battery" was a standard rule of thumb -but panels were seldom more than 55 watts, so 110 watts (6 1/2 A) was about standard for a pair of golf carts. That's a C/34 charge rate, max. </div><div><br></div><div>This past spring Windy and I revised that spreadsheet to reflect modern sizing and economics. It now works with any module cell count, for example. Contact me off list if you'd like a copy. (Be patient for the reply as I'm currently traveling.) </div><div><br>On Sep 15, 2015, at 6:04 PM, "Dave" <<a href="mailto:dave@independentpowerllc.com">dave@independentpowerllc.com</a>> wrote:<br><br></div><blockquote type="cite"><div><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><meta name="Generator" content="Microsoft Word 12 (filtered medium)"><style><!--
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</o:shapelayout></xml><![endif]--><div class="WordSection1"><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The AEE catalog battery sizing template works well as it allows you to dial back the days of autonomy needed. As I remember the old Dankoff Solar battery sizing method pushed the watt hour size of battery banks to large, and expensive, levels.<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">The collective experience of this group, and others, has emphasized designing off grid pv system's where the primary consideration is ample PV array sizing and where the storage battery is sized in the C/10 range. With lower module prices this has been practical for a few years now and it has been demonstrated that smaller watt hour battery banks have proven to be not only cost savers but also perform well for years as they live in a system where they are very likely to be fully charged on a regular basis.<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">Even here in northern Vermont where we experience late fall and winter daily peak sun hours in the 1 hr/day average range, designing large battery banks has been frowned on for many years out of my shop. Oversize the pv array and run the generator when needed.<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">David Palumbo <o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Independent Power LLC<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">462 Solar Way Drive<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hyde Park, VT 05655<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">802-371-8678 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"><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><div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in"><p class="MsoNormal"><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 [<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>] <b>On Behalf Of </b>Chris Mason<br><b>Sent:</b> Tuesday, September 15, 2015 5:39 PM<br><b>To:</b> RE-wrenches<br><b>Subject:</b> Re: [RE-wrenches] Battery bank calculator<o:p></o:p></span></p></div><p class="MsoNormal"><o:p> </o:p></p><p>Homer can do it but it is expensive.<br><a href="http://www.homerenergy.com">http://www.homerenergy.com</a><o:p></o:p></p><div><p class="MsoNormal">On Sep 15, 2015 9:31 AM, "RE Ellison" <<a href="mailto:reellison@gmail.com">reellison@gmail.com</a>> wrote:<o:p></o:p></p><p class="MsoNormal" style="margin-bottom:12.0pt">I don't think it can be done accurately with a sizing tool i've actually never heard of a tool at least not that I can remember<br><br>There's far too many variables.<br>Everything from loads to solar isolation as well as the habits of the individual occupants and the appliance selection in the home<br><br>The old joke used to be calculate what you needed for three days and then double it as far as battery bank size<br><br>Just a few thoughts, batten five dollars will get your cuppa coffee and a lot of convenient stores<br><br>Bob Ellison<br><br><br><br>> On Sep 15, 2015, at 9:21 AM, gary easton <<a href="mailto:gary@arp-solar.com">gary@arp-solar.com</a>> wrote:<br>><br>> anyone have a suggestion for a battery bank sizing tool?<br>><br>> --<br>> Sent from Gmail Mobile<br>> _______________________________________________<br>> List sponsored by Redwood Alliance<br>><br>> List Address: <a href="mailto:RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a><br>><br>> Change listserver email address & settings:<br>> <a href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org" target="_blank">http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a><br>><br>> List-Archive: <a href="http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html" target="_blank">http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html</a><br>><br>> List rules & etiquette:<br>> <a href="http://www.re-wrenches.org/etiquette.htm" target="_blank">www.re-wrenches.org/etiquette.htm</a><br>><br>> Check out or update participant bios:<br>> <a href="http://www.members.re-wrenches.org" 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