We had an install with the Q.PEAK DUO BLK-G6+ 340 where there was a bad diode in a panel or two, and production was reduced by approximately 25% +/- on each panel. Same with some Q.PEAK DUO BLK-L G5.2 400 watt panels and Q.PEAK DUO BLK-L G5.3 400 watt panels. All those installs were with Enphase or SolarEdge so it was pretty easy to diagnose remotely. I believe in all those cases the failure happened within the first year of being installed. I think those installs were all around 2020 or 2021 maybe, and we didn't have any issues with QCells before or after that time period.
Adam Katzman (he/him) Autonomous Energies | Owner/Operator www.AutonomousEnergies.com <http://www.autonomousenergies.com> (518) 567-1468 On Tue, Feb 10, 2026 at 4:16 PM Dave Tedeyan via RE-wrenches < [email protected]> wrote: > Hi All, > > 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. > > 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. > > So, I can only think of two things that might be at play here: > 1. Maybe these modules are just crap, and are not at all performing to > spec. > 2. Maybe the Tigo devices are causing issues. > > 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! > > Thanks for the consideration! > Cheers, > Dave > -- > > Dave Tedeyan, P.E. > Owner | Sungineer Solar > p: he | him | his > a: 1653 Slaterville Rd. | Ithaca, NY 14850 > w: www.sungineersolar.com <http://www.sungineersolar.com/> > c: (607) 270-0370 > _______________________________________________ > List sponsored by Redwood Alliance > > Pay optional member dues here: http://re-wrenches.org > > List Address: [email protected] > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > There are two list archives for searching. When one doesn't work, try the > other: > https://www.mail-archive.com/[email protected]/ > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > http://www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > http://www.members.re-wrenches.org > >
_______________________________________________ List sponsored by Redwood Alliance Pay optional member dues here: http://re-wrenches.org List Address: [email protected] Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org There are two list archives for searching. When one doesn't work, try the other: https://www.mail-archive.com/[email protected]/ http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: http://www.re-wrenches.org/etiquette.htm Check out or update participant bios: http://www.members.re-wrenches.org
