[RE-wrenches] Voltage Degradation with Uni-Solar laminate

[Allan Sindelar]

Luke,
I have never worked with Uni-Solar laminates, although I expect to for the first time this summer, at 12,800' in the White-Inyo mountains, but that's another story. I installed one small cabin system with US64s in 1999 (the rancher wanted modules that would keep performing with a few vandals' bullet holes, which never happened) and they continue to perform as new. 

So take my two comments with that disclaimer in mind. First, you measured only 63% of rated output. That's pretty low at the controller, even if the roof is hot. Could there be something else to search for as a cause?

Assuming it's indeed simply weak voltage, consider a Midnite Classic 200 or 250, to give the voltage window to allow repairing to a higher nominal input, maybe 72 or 96 volts, so that the charge voltage will always be higher than battery voltage. 

Allan

> On May 31, 2015, at 11:55 AM, Luke Christy <sgsrenewables at gmail.com> 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
> 
> NABCEP Certified PV Installation Professional™: Certification #031409-25 
> NABCEP Certified Solar Heating Installer™: Certification #ST032611-03       
> CoSEIA Certified PV Installer 
> 
> Solar Gain Services, LLC
> PO Box 531
> Monte Vista, CO. 81144
> SGSRenewables at Gmail.com
> 719.588.3044
> www.sgsrenewables.com
> 
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