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
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