How to test a Solar Panel before Installation

[Weight]

Trebor, yes thank you. My mistake.

 

[jimindenver]

Dont know what to tell you Jim.  The industry does not agree with your test results.  But I am sure the test peramiters are not the same.  

This is why I only recommend Renogy.  The quality and preformance is uniform unlike cheaply made unknown brands.  

The cost difference is not worth it in the long run buying cheap panels. 

You get what you pay for.

This is true. I don't test in a lab, I test in real life. The panels I have tested were not unknowns. CanadianSolar, Bosch, SchottPoly, the only panels that are not big name are the ones on my roof, the Navajo Solar.

The CanadianSolar and SchottPoly are old now and you could see why the industry considered The mono to be more efficient in a grid tied situation. The 220w Canadian solar had a smaller frame than the SchottPoly. It produced a higher voltage too. That said in a off grid situation such as we need it produced 12a tracking the sun vs the 15a the 230w Schottpoly did.

The 245w Bocsh mono again produced a higher voltage than the 250w Navajo Poly. The difference was the difference in footprint was just a inch less of cell length inside of the same size frame as the Navajo has. More efficient yes but not in the real world. There the There the mono maxed out at 17a while the poly did 18.5a. Lower voltage but higher amps is across the board with polys, most easily seen in 12v panels. In a PWM system there is nothing to use the extra volt a mono puts out but the higher Isc/Imp of the poly is directly usable for charging.

The biggest difference is in cloudy conditions where it doesn't take much to drop the CanadianSolar panel to drop to .48a on a Mppt controller. The Bosch dropped to 2.38a. The SchottPoly and the Navajo drop more according to just how thick the clouds are. I could see 4-5a out of the SchottPoly in clouds thick enough that I didn't know where to point the panel to track the sun. The three Navajos on my roof produce 20a when its cloudy and 10a amps in the rain. Impressive numbers they may not be but it has always been enough to keep the trailer off the generator until the sun came back even if I did need to use propane to cook and heat water.

Right now I am in a heavily treed lot in Prescott. The trailer hasn't seen a clear shot at the sun yet and its panels are in series. I'm still seeing up to 10a even though multiple panels are shaded. I need to switch to parallel in the event one or two panels get a good look at the sun but I should be able to find a spot that will give me a few hours of full sun. Then I can use the truck to chase the sun and even if I had to rely on just its panel, I would be a happy camper.

You have to remember that I don't test to sell anything and I don't have any reason to make anything look good or bad. I just observe, record and report my real life results. Not many people get their hands on multiple panels and/or controllers. I know of some that have benefited from my research, some run generators to make up for the fact they don't camp in a lab.

I also studied the effects of shading, mismatched panels, altitude and temperature variations. I figured out how to do what others said wasn't possible by understanding how to get the most out of the sun in real world conditions, not by tossing a kit up there and calling it good.

 

[GotSmart]

So you were compairing an old banana to a new lemon and a cumquat.  

As I said, and continue to say ~~~ The new panels are much more efficient than the old panels.

Today building a solar system from different components is not the same as it was.  I trust the people that have to stand behind a product with their reputation (designed and built by professionals) to sell me a kit.  Rather than chosing what ever panel is cheapest that day with a high dollar wizz bang controller to force the incoming power to behave.  

You can have your mis matched panels.  

There are thousands of possibilities in any solar collection situation.  I just happen to have enough education, and the understanding that I will never know everything. I will go by the book and get a quality kit from a vender with a proven track record.  So I spend a few dollars more.  I think of that as insurance that the box system will function in Olympia Washington as well as Quartzsite Arizona. If there is a problem, one phone call will get a solution.

 

[jimindenver]

The panels were new at the time of purchase. I think I may have been at this longer than you give me credit for. The advertising, opps I mean testing said the same then as it does now. Go figure. I see Renogy is still selling rebranded Tracer controllers too.

Like I said, I'd love to sit down ad yak with ya but bring some of the new panels cuz I have a pair of Morningstar controllers, it would be a simple thing to do a real side by side with my Navajos complete with computer analysis.

S far as the mismatched panels go, I had MPPT manufacturers telling me it would be fine but I couldn't see how the vastly different voltage ranges and responses to conditions could work well so I ran my own test to find it confuses the controllers MPPT program as it tried to find a sweet spot. The same is true when one panel in a set in series is shaded. That and the low panel rules the roost since there is no way for the more powerful panels to force it to raise its voltage.

I still don't see how the more efficient monos with higher voltage and lower amps is suppose to help the small time user with a PWM controller.

 

[dr_nelson]

I am still alive (sorry, the world isn't home   ).

It was noon and it had very few clouds. I tested both panels, made sure there was no shading on the panel and I tilted them towards the sun.

Panel 1
Test Result 23.2 V (Voc), 8.59 A (Isc)
Spec says 24.06 V (Voc), 9.77 A (Isc)

Panel 2:
Test Result 23.1 V (Voc), 8.47 A (Isc)
Specs says 24.06 V (Voc), 9.77 A (Isc)

Now, these numbers mean nothing to me as I have no clue. Are these numbers good or not good?
I am still thinking to return them because they left the factory with dents in the aluminum frame.

 

[jimindenver]

What do you mean by a few clouds? Was the sun behind a cloud or even haze while you tested them? In full sun I would expect a new panel to meet if not exceed the rating. Anything but full sun and you are not giving the panel a fair chance. In between clouds I would consider full sun and may even expect cloud effect that should have given a boost. I would not accept a panel falling short of it's rating especially amps in full sun.

 

[dr_nelson]

Thanks JimInDenver!

Just tested again, in full sun without clouds covering the sun (1:50 PM).
Test Result: 49.9 V (Voc), 9.80 A (Isc)
Spec says 24.06 V (Voc), 9.77 A (Isc)

Looks like Volts is double, and Amps is exceeded. Can this be considered "good"?