Used Panels not Activating Controller (Edit, Low Power)

[retrodog]

I got some used SolarWorld (SW 235 Poly) panels last weekend. Finally got them out to test. Tested them with a DMM. The current rated/measured is 8.35/7.57, and the VOC is 37.0/35.5. The other panel is very close to these numbers as well.

I was expecting at least some diminished performance, say down around 80%, but they are not eve activating my Victron 100/20 controller. I can switch over to one of the new Harbor Freight 100W panels and I'm getting 89W from them, charging to the battery.

The polarity is fine. Is there a setting I'm missing? The controller is connected to a "half depleted" Dakota 12V 54ah LiFePO4 battery.

Edit: Bad Connector. Fixed it. Power is only about 150 right now, but at least it's charging the system. Clouds rolling over occasionally so there's that. The Houston area is a little iffy sometimes.

 

[FilterGuy]

The Houston area is a little iffy sometimes.

Careful..... to some Texans I know, those are fight'n words!!! ?

 

[retrodog]

Looks like both of them are generating 150W max, when the sun it out strong. The joy of used panels, I suppose. At least the two are almost identical, in terms of output. So I'd just chock it up to current state of degradation.

 

[FilterGuy]

Looks like both of them are generating 150W max, when the sun it out strong. The joy of used panels, I suppose. At least the two are almost identical, in terms of output. So I'd just chock it up to current state of degradation.

There is probably some degradation, but keep in mind that panels are rated at 'Standard Testing Conditions'. Unfortunately, it is unusual that STC is met in any real-world installations. Consequently, even new installs usually don't produce as much as the rated power of the panels.

The value of an STC rating is that it allows the comparison of different panels under the same conditions. This is good, but even that can be misleading. As an example, if a panel is better at dissipating heat, it might perform better than an identically rated panel that does not dissipate heat as well. Another example of things that STC misses is how well the panel can harvest energy from off-angle sunlight.

 

[acdoctor]

Do you know how old they are? I am interested to know how many years it took to go from 235 to 150

 

[retrodog]

Do you know how old they are? I am interested to know how many years it took to go from 235 to 150

I do not. But I wouldn't assume that it's an actual 85W drop. AS FilterGuy stated above, they probably didn't produce the rated value when they were new. And it's October, so there's that too. Without having tested them new under these same conditions, I guess the variance would be an guess (by me) or an "educated guess" by others on here.

 

[Ozark Tinkering]

I'm new to solar but is October the best time of the year to test full output? My panels' production falls off by 20% in October from Sept.

 

[retrodog]

I'm new to solar but is October the best time of the year to test full output? My panels' production falls off by 20% in October from Sept.

Located in Houston TX area. We get pretty good sun year'round. I need to correct this data though. I think I was using bad cables or connectors for this initial test. I checked them again about a month or so later, in series, with good wire and connectors and was getting 175 per panel. I'm going to mount them on the roof of my shed, next to the four Harbor Freight 100W panels. Those have been working very well.