Default Solar Panel Output ?

12-17-15, 04:15 AM

I purchased a 100W (2*50W) 12V folding mono solar panel with 15A solar charge controller from eco-worthy. They just arrived so I wanted to test them using a multimeter. I disconnected all the wires from the charge controller so that I could test each one independently. I tested in bright sunlight at high noon here on the East Coast. The stickers on each panel say the VOC is 22.41V and the ISC is 6.2 amp. One panel read 22.14V and the other 22.12V but noticed they started to drop a few volts rather quickly. My main concern is the fact that the ISC on both was lower than the rating (one was 3.12 amps and the other was 2.89. Do I have a problem here that I need to address with the mfg? Any help would be much appreciated.

where2 · 12-17-15, 06:16 PM

Unless you have a method to illuminate the panels with the equivalent to sunlight at 1000W per square meter, you're never going to see the values on the stickers on the panels. Variables like time of day, day of year, particulates in the atmosphere, temperature, wind, all have effects on what you will measure when you short the panels and try to measure your own ISC.

This website I just randomly found using Google seems to do a fair job of explaining the common solar panel testing conditions (STC) which are typically what is listed on panel rating stickers:
Standard Test Conditions (STC) vs. Normal Operating Cell temperature (NOCT)

oil pan 4 · 12-19-15, 10:13 AM

That is very typical.
In the world of solar just because you buy 1 watt of solar does not mean you will get 1 watt of power where you need it.

I have bought panels from ecoworty, their panels are kind of cheap but they work as I expected them to.
I have also found some of their numbers to be just plain wrong, I don't think they were trying to deceive any one, because the panels I bought were putting out much more volts than they speced.
As for their charge controller, no thanks, wouldn't connect them to anything I actually care about.

Are you sure they were pointed precisely orthogonal to the sun?
I was able to at least get rated amps out of mine when pointed at the sun, once I lay them flat (my application) their power production drops to around half of rated. Which is what you should expect.

Now ISC is short circuit current. Were you short circuiting them or were they connected to the charge controller?

12-17-15, 04:15 AM	#1
petertrieu Guest Posts: n/a	Default Solar Panel Output ? I purchased a 100W (2*50W) 12V folding mono solar panel with 15A solar charge controller from eco-worthy. They just arrived so I wanted to test them using a multimeter. I disconnected all the wires from the charge controller so that I could test each one independently. I tested in bright sunlight at high noon here on the East Coast. The stickers on each panel say the VOC is 22.41V and the ISC is 6.2 amp. One panel read 22.14V and the other 22.12V but noticed they started to drop a few volts rather quickly. My main concern is the fact that the ISC on both was lower than the rating (one was 3.12 amps and the other was 2.89. Do I have a problem here that I need to address with the mfg? Any help would be much appreciated.

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12-17-15, 06:16 PM	#2
where2 DIY Geek Join Date: Apr 2013 Location: Sunny Florida Posts: 401 Thanks: 74 Thanked 83 Times in 73 Posts	Unless you have a method to illuminate the panels with the equivalent to sunlight at 1000W per square meter, you're never going to see the values on the stickers on the panels. Variables like time of day, day of year, particulates in the atmosphere, temperature, wind, all have effects on what you will measure when you short the panels and try to measure your own ISC. This website I just randomly found using Google seems to do a fair job of explaining the common solar panel testing conditions (STC) which are typically what is listed on panel rating stickers: Standard Test Conditions (STC) vs. Normal Operating Cell temperature (NOCT)

12-19-15, 10:13 AM	#3
oil pan 4 Land owner Join Date: Nov 2012 Location: NM Posts: 1,026 Thanks: 12 Thanked 127 Times in 107 Posts	That is very typical. In the world of solar just because you buy 1 watt of solar does not mean you will get 1 watt of power where you need it. I have bought panels from ecoworty, their panels are kind of cheap but they work as I expected them to. I have also found some of their numbers to be just plain wrong, I don't think they were trying to deceive any one, because the panels I bought were putting out much more volts than they speced. As for their charge controller, no thanks, wouldn't connect them to anything I actually care about. Are you sure they were pointed precisely orthogonal to the sun? I was able to at least get rated amps out of mine when pointed at the sun, once I lay them flat (my application) their power production drops to around half of rated. Which is what you should expect. Now ISC is short circuit current. Were you short circuiting them or were they connected to the charge controller?