<div dir="ltr"><div>Brian<br>Can you do a solmetric type test, when you performed the amp test the volts were at near "0" so the test does not show an accurate value, you said the modules are brown this is not good but are they checked because if so you are done needs new modules. I would suggest doing some additional testing, is it selling, and at what amount, whats going into or out of the batteries at that time, what inverter is it, trace 24 I would assume, if it is selling is the inverter capable of selling more than it is or is at the limit, I need more numbers to get a better understanding if there is even a problem. You can adjust "Sell" down to perform a test and see if the DC climbs, also you can set the MX amp down too. <br></div><div>Jerry<br></div> <br></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Aug 25, 2016 at 4:39 AM, Brian Mehalic <span dir="ltr"><<a href="mailto:brian@solarenergy.org" target="_blank">brian@solarenergy.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">If it is a module issue it could be bad solder joints, shorted diodes, or a combination of both. I just curve traced 12 12-year old KC120s - all except 2 tested fine for Voc with a DMM (2 were totally dead). However with the curve tracer they all exhibited more of an IV "angle" than a curve, going straightish from expected Isc to a Voc that represented only 1/2 a modules worth of voltage. When we added it all up it made sense based on the MPP that we initially observed the inverter to be operating at. They'll be coming off the roof soon and we'll be able to do better testing (and check the accessible diodes).<div><br></div></div><div class="gmail_extra"><br clear="all"><div><div data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><br></div><div>Brian Mehalic <br>NABCEP Certified Solar PV Installation Professional™ R031508-59</div><div><a href="tel:520.204.6639" value="+15202046639" target="_blank">520.204.6639</a><br><div><br></div><div><div><div>Solar Energy International<br><a href="http://www.solarenergy.org" target="_blank">http://www.solarenergy.org</a></div></div></div></div><div><br></div><div>SEI Professional Services</div><div><a href="http://www.seisolarpros.com" target="_blank"><span style="font-size:12.8px">http://www.s</span>eisolarpros.com</a><br></div><div><br></div></div></div></div></div></div></div></div><div><div class="h5">
<br><div class="gmail_quote">On Thu, Aug 25, 2016 at 8:24 AM, Steve Bell <span dir="ltr"><<a href="mailto:sbell@morningstarcorp.com" target="_blank">sbell@morningstarcorp.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hello Allan,<div><br></div><div>Did you check the Voc of each string? Is it possible that there could one or more shorted bypass diodes in the modules?</div><div><br></div><div>Just a thought.</div><div><br></div><div>Steve Bell</div><div>Morningstar tech support</div></div><div class="gmail_extra"><br><div class="gmail_quote"><div><div>On Thu, Aug 25, 2016 at 8:04 AM, Allan Sindelar <span dir="ltr"><<a href="mailto:allan@sindelarsolar.com" target="_blank">allan@sindelarsolar.com</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div>
<div style="background-color:rgb(255,255,255);color:rgb(0,0,0)" bgcolor="#FFFFFF" text="#000000">
Wrenches,<br>
Here's one I haven't seen before. 1997 grid-tie battery backup
system that was one of my first, although actual installation was by
another before I was licensed. 16 BP 275, 36-cell 12V modules, the
standard of that time. Early Outback MX60 replaced C40 around 2005;
array rewired to four 48V strings of four modules at that time,
serving a 24V battery bank. Tested with an end-of-life 9-year-old
AGM battery bank in the system, but in Sell mode with a 26.4V Sell
voltage setpoint.<br>
<br>
At 11 am, 68ºF, 900W/m<sup>2</sup> on the Daystar, with the array
under charge, I measured 3.5A, 3.4A, 2.4A, and 3.6A.
Short-circuiting each string, I measured 4.0A, 3.7A, 3.8A, and 3.7A.
Original rating was 4.45A, so except for the third string, current
is what I'd reasonably expect from 20-year-old module degradation.
However, watching the periodic MPPT sweep from the MX60 at the
array, the maximum power point voltage for the entire 48V array
settled at 14.6A at 37.2V, or about 540 watts from a 1,200W
(originally rated) array.<br>
<br>
I have commonly seen the current reduce substantially with
age-related degradation, while the MPP voltage remains fairly close
to original. I have never seen the voltage drop this far - an
average of 9.3V MPP per each 12V module. All of the cells are
seriously browned. I have other systems out there with the same
modules of similar age that don't exhibit this weird behavior. Can
anyone help me understand why the MPP voltage would drop so far
below what is typical?<br>
<br>
There is a slight possibility of corroded buried input conductors,
because of a serious but corrected issue of galvanic corrosion from
a ground fault (a Romex connector pinching a conductor and allowing
seepage to ground). This was corrected years ago, but the input
conductors were direct burial for ~100' and there was never a
bonding conductor between the array and the house, so there is a
potential for corrosion damage. However, the voltage measured at
both ends while charging was identical, so I think that would
indicate that high conductor resistance isn't the issue.<br>
<br>
As usual, thank you for the collective and individual wisdom shared
here.<span><font color="#888888"><br>
Allan<br>
<div>-- <br>
<div>
<p class="MsoNormal"><b>Allan Sindelar</b><br>
<span style="font-size:10.0pt"><a href="mailto:allan@sindelarsolar.com" target="_blank">allan@sindelarsolar.com</a></span><br>
<span style="font-size:10.0pt">NABCEP Certified PV
Installation Professional<br>
NABCEP Certified Technical Sales Professional<br>
New Mexico EE98J Journeyman Electrician<br>
Founder (Retired), <span>Positive
Energy,
Inc.</span><br>
<b><a href="tel:505%20780-2738" value="+15057802738" target="_blank">505 780-2738</a> cell</b><br>
<br>
<b><u></u><u></u></b></span></p>
<p class="MsoNormal"><u></u> <u></u></p>
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