<div dir='auto'><div>We have seen a lot of Qcells with one diode failing and dropping module production by 1/3.</div><div dir="auto">I have a Solmetric curve tracer I am looking to part with...</div><div><br></div><div data-smartmail="gmail_signature">-Glenn</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Feb 11, 2026 09:26, Dave Tedeyan via RE-wrenches <re-wrenches@lists.re-wrenches.org> wrote:<br type="attribution" /><blockquote class="quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">I must admit, this is a little embarrassing... this is what I get for trying to work with a head cold. I didn't remember that there was a change order on this one, and the original contract was for a larger system than what eventually got installed. I was looking at the producion estimate from the original larger system, which was around 17MWh/year. The actual production estimate is closer to 14.3MWh, and the system has averaged 13.5MWh over the past 5 years. So, 94% is not nearly as bad as I originally thought, although it is still not good either. <div><br /></div><div>The voltages that I am seeing on the Sunny Portal monitoring are still lower than I would expect. I think it is still worth checking out with an IR scan once the snow goes away and the sun comes back here in upstate NY. The recommendations for doing a curve trace would be the best troubleshooting step, although I have not yet invested in one of those. All this still leads me to believe that these Qcell modules may be not quite be performing to spec, but they are not as ridiculously far off as I feared. </div><div><br /></div><div>Cheers,</div><div>Dave</div></div><br /><div><div dir="ltr">On Tue, Feb 10, 2026 at 8:50 PM Roy Rakobitsch via RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a>> wrote:<br /></div><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb( 204 , 204 , 204 );padding-left:1ex"><div dir="auto"><div>It would be fairly easy to spot bypass diode issues or cell current imbalance issues with a hand-held IR imager on a decently sunny day. Maybe time to go on the roof and take a peek?</div><div dir="auto"><br /></div><div><br /></div><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div style="color:rgb( 34 , 34 , 34 )">Roy Rakobitsch</div><div style="color:rgb( 34 , 34 , 34 )"><br /></div><div style="color:rgb( 34 , 34 , 34 )">Windsine LLC</div><div style="color:rgb( 34 , 34 , 34 )">631-514-4166</div></div></div></div></div></div></div></div><br /><div class="elided-text"><div dir="ltr">On Tue, Feb 10, 2026, 18:25 Jay via RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a>> wrote:<br /></div><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb( 204 , 204 , 204 );padding-left:1ex"><div dir="auto"><div dir="ltr"></div><div dir="ltr">Looking at it from performance ie watts, how far off does it appear to be?</div><div dir="ltr"><br /></div><div dir="ltr">Jay</div><div dir="ltr"><br /></div><div dir="ltr"><br /></div><div dir="ltr"><br /><blockquote>On Feb 10, 2026, at 2:07 PM, Dave Tedeyan via RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a>> wrote:<br /><br /></blockquote></div><blockquote><div dir="ltr"><div dir="ltr"><div>Hi All, </div><div><br /></div><div>I was just reviewing a site installed about 5 years ago and am finding it is not doing nearly as well as I would have expected. Most of our sites produce relatively close to our projections, but this one is pretty far off. There are 3 strings of 12 Q.PEAK DUO BLK-G6+ modules. Two strings go to a 7.7kw inverter and one string goes to a 3.8kw inverter - both of which are the -41 series SMA inverters. There are Tigo TS4-R-F rapid shutdown devices on all the modules.</div><div><br /></div><div>Vmp for 12 of these panels should be about 407V at STC. At 50C (which is really hot for upstate NY), the Vmp should be around 380V. On a perfect summer day, I am seeing Vmp of around 320V. On a perfect spring day (cooler, with some power clipping, I am seeing Vmp of around 355V. And on a perfect winter day (when there was no snow) Vmp is around 365V. All three strings are pretty consistent with each other, so I don't think that there are specific installation issues with any panels, unless we managed to forget to wire in two panels in all three strings which is extremely unlikely.</div><div><br /></div><div>So, I can only think of two things that might be at play here:</div><div>1. Maybe these modules are just crap, and are not at all performing to spec.</div><div>2. Maybe the Tigo devices are causing issues. </div><div><br /></div><div>Has anyone out there experienced production issues like this? Everything appears normal, it is on an open rooftop, and there are not things like partial shading, weeds, bird poop, or other soiling affecting the modules. I don't have another site with the same modules that also has good monitoring data, but maybe some of you do!</div><div><br /></div><div>Thanks for the consideration!</div><div>Cheers, </div><div>Dave</div>-- <br /><div dir="ltr"><div dir="ltr"><br style="color:rgb( 34 , 34 , 34 )" /><div dir="ltr" style="color:rgb( 34 , 34 , 34 )"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"></div></div></div><div dir="ltr"><table cellpadding="0" cellspacing="0" style="border-spacing:0px;border-collapse:collapse;color:rgb( 68 , 68 , 68 );width:525px;font-size:11pt;font-family:'arial' , sans-serif"><tbody><tr><td width="125" valign="top" rowspan="6" style="padding:0px 10px 0px 0px;font-size:10pt;border-right:1px solid rgb( 236 , 189 , 0 );width:125px;vertical-align:top"><img style="color:rgb( 32 , 33 , 36 );font-family:'arial' , 'helvetica' , sans-serif;font-size:small" width="96" height="95" src="https://ci3.googleusercontent.com/mail-sig/AIorK4zoZ4JdaR79CFcLmy74s-VRVaVovMEuRmw5pzk3XBT09h8ZNlFbMgJ4yHW2Uxf91_2codJGB4DALADN" /></td><td style="padding:0px 0px 0px 10px"><table cellpadding="0" cellspacing="0" style="border-spacing:0px;border-collapse:collapse;background-color:transparent"><tbody><tr><td valign="top" style="padding:0px 0px 5px 10px;width:400px;vertical-align:top"><span style="color:rgb( 236 , 189 , 0 );font-size:11pt;font-weight:700">Dave Tedeyan, P.E.<br /></span><span style="font-size:11pt;font-weight:700"><font color="#ecbd00">Owner | Sungineer Solar</font><br /></span></td></tr><tr><td valign="top" style="padding:5px 0px 5px 10px;font-size:10pt;vertical-align:top;line-height:17px"><span style="color:rgb( 236 , 189 , 0 )"><span style="font-weight:700">p: </span></span><span style="font-size:10pt;color:rgb( 0 , 0 , 0 )">he | him | his</span><span style="color:rgb( 236 , 189 , 0 )"><span style="font-weight:700"><br />a: </span></span><span style="font-size:10pt;color:rgb( 0 , 0 , 0 )">1653 Slaterville Rd.</span> <span style="font-size:10pt;color:rgb( 0 , 0 , 0 )">| Ithaca, NY 14850</span><br /><span style="color:rgb( 236 , 189 , 0 )"><span style="font-weight:700">w:</span></span><a href="http://www.sungineersolar.com/" style="color:rgb( 51 , 122 , 183 );background-color:transparent"><span style="font-size:10pt;color:rgb( 0 , 0 , 0 )"> www.sungineersolar.com</span></a><br /><span style="color:rgb( 236 , 189 , 0 )"><span style="font-weight:700">c:</span></span><span style="font-size:10pt;color:rgb( 0 , 0 , 0 )"> (607) 270-0370</span></td></tr></tbody></table></td></tr></tbody></table></div></div></div></div></div></div>
_______________________________________________<br />List sponsored by Redwood Alliance<br /><br />Pay optional member dues here: <a href="http://re-wrenches.org">http://re-wrenches.org</a><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">http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a><br /><br />There are two list archives for searching. When one doesn't work, try the other:<br /><a href="https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/">https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/</a><br /><a href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org">http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a><br /><br />List rules & etiquette:<br /><a href="http://www.re-wrenches.org/etiquette.htm">http://www.re-wrenches.org/etiquette.htm</a><br /><br />Check out or update participant bios:<br /><a href="http://www.members.re-wrenches.org">http://www.members.re-wrenches.org</a><br /><br /></div></blockquote></div>_______________________________________________<br />
List sponsored by Redwood Alliance<br />
<br />
Pay optional member dues here: <a href="http://re-wrenches.org">http://re-wrenches.org</a><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">http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a><br />
<br />
There are two list archives for searching. When one doesn't work, try the other:<br />
<a href="https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/">https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/</a><br />
<a href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org">http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a><br />
<br />
List rules & etiquette:<br />
<a href="http://www.re-wrenches.org/etiquette.htm">http://www.re-wrenches.org/etiquette.htm</a><br />
<br />
Check out or update participant bios:<br />
<a href="http://www.members.re-wrenches.org">http://www.members.re-wrenches.org</a><br />
<br />
</blockquote></div>
_______________________________________________<br />
List sponsored by Redwood Alliance<br />
<br />
Pay optional member dues here: <a href="http://re-wrenches.org">http://re-wrenches.org</a><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">http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a><br />
<br />
There are two list archives for searching. When one doesn't work, try the other:<br />
<a href="https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/">https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/</a><br />
<a href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org">http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a><br />
<br />
List rules & etiquette:<br />
<a href="http://www.re-wrenches.org/etiquette.htm">http://www.re-wrenches.org/etiquette.htm</a><br />
<br />
Check out or update participant bios:<br />
<a href="http://www.members.re-wrenches.org">http://www.members.re-wrenches.org</a><br />
<br />
</blockquote></div>
</blockquote></div><br></div>