I second Jay. If one string is significantly lower, I’d check each module in the string. Could be a bad module.
Randy > On May 31, 2015, at 1:23 PM, jay peltz <jay.pe...@gmail.com> wrote: > > HI Luke, > > To add here. I'm unclear if you have measured each string or the whole array > at 71v. > I would check each string for voc/isc. > > And then if they are consistent, I agree that putting 2 strings in series > with a new controller might help out. > You can try it with the MX-60 as you are at only 142v. If it works better > then a new higher voltage CC would be required for winter higher voc. > > Let us know what you find out. > > jay > > > On 5/31/2015 11:55 AM, Luke Christy wrote: >> Hello Off-Grid Wrenches, >> >> I recently made a periodic maintenance visit to a residential off-grid >> system I take care of here in Southern CO, and discovered an interesting >> problem. >> >> This system has an array of 48x Uni-Solar PVL-68 laminate modules applied >> directly to standing-seam metal roofing. >> >> The data logging on the controller (Outback MX-60) indicated that the system >> was having trouble completing a charge cycle and going to float. Initially I >> assumed was due to heavy electrical use by the occupants (renters). After a >> little checking, I noticed that the module string voltage was only about >> 0.5V above the battery voltage! >> This was a cool late morning, with full sun, and the array was charging >> almost 2kW at 54.5V. The module strings were running at 55V. I've noticed >> the module voltage being lower than I'd like before, but it has never been >> this low. I suspect this is the real reason the system hasn't been able to >> complete a charge cycle. >> >> By removing the loads I was able to get an open-circuit voltage of 71V, but >> that still seems pretty low. >> >> Has anyone else experienced a voltage degradation issue with the Uni-Solar >> laminate? What was the expected annual voltage degradation for this >> technology? >> >> These modules do have some age on them. The system was installed about 15 >> years ago (by a competent installer who is now retired). The system was >> installed before MPPT controllers were common, so I assume the modules are >> wired in strings of 4 for 48V nominal. >> >> Any experiences or opinions are appreciated. >> Thanks in advance. >> >> -Luke >> >> >> Luke Christy >> >> > > Jay Peltz > Peltz Power > jay.pe...@gmail.com > <mailto:jay.pe...@gmail.com>_______________________________________________ > List sponsored by Redwood Alliance > > List Address: RE-wrenches@lists.re-wrenches.org > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org >
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