<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Allan,<div class=""><br class=""></div><div class="">The battery "pair" is operating in parallel so the current flowing through that string will be divided between the two. This means that each battery in the parallel set is only being discharged half of what the others in the string are. So, of course, those batteries will be lasting longer since they have half the DoD each day. A very strange setup, I’ve never seen this. Since I rarely see a true battery failure (most are damaged by the owner) I can’t say that I’ve noticed any pattern.<div apple-content-edited="true" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class="">Larry Crutcher<br class="">Starlight Solar Power Systems<br class=""></div><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""></div></div></div>
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<br class=""><div><div class="">On Sep 30, 2015, at 8:43 PM, Allan Sindelar <<a href="mailto:allan@sindelarsolar.com" class="">allan@sindelarsolar.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
<meta http-equiv="content-type" content="text/html; charset=utf-8" class="">
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Wrenches, especially the grizzled ones,<br class="">
I was referred to a couple for off grid service about 75 miles from
here. They have an older homeowner-built 24V system (that I haven't
seen yet) and have lived with it for decades. They have ten L16s in
two parallel strings. I questioned this when I first heard it, but
the owner told me that the most positive cell is the one that always
fails first, and he hates the effort of periodically rotating his
batteries, so the battery nearest the positive cable has another L16
in parallel with only this battery. He explained that he has lived
this way for thirty years. I don't yet know what life they have
gotten from their battery sets, but until recently they lived on
750W of PV, and now have around 1kW - not a large array.<br class="">
<br class="">
I respectfully replied that in nearly thirty years in the field,
this is the first time I had heard of this approach. My own
experience is that while sometimes I had sometimes seen marginally
more water consumption in the lead positive cells as they aged, when
I had tested for failed cells in old strings, the failed cells
tended to be randomly located, and not frequently enough at the
positive end to suggest a pattern. I had also long ago read
(Surrette's manual?) that rotating the lead cell is good practice,
but unless a system has a single series string, wired to make this
possible, nobody ever did this rotation, and it didn't appear to
make a noticeable difference in long-term performance.<br class="">
<br class="">
Has anyone else heard of this approach? Is there validity to the
logic? What can I learn here that I didn't know?<br class="">
Thank you,<br class="">
Allan<br class="">
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<div class="WordSection1"><p class="MsoNormal"><b class="">Allan Sindelar</b><br class="">
<span style="font-size:10.0pt" class=""><a href="mailto:allan@sindelarsolar.com" class=""></a><a class="moz-txt-link-abbreviated" href="mailto:allan@sindelarsolar.com">allan@sindelarsolar.com</a></span><br class="">
<span style="font-size:10.0pt" class="">NABCEP Certified PV
Installation Professional<br class="">
NABCEP Certified Technical Sales Professional<br class="">
New Mexico EE98J Journeyman Electrician<br class="">
Founder (Retired), <span style="mso-bidi-font-weight:bold" class="">Positive
Energy,
Inc.</span><br class="">
<b class="">505 780-2738 cell</b><br style="mso-special-character:line-break" class="">
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