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noobynoob

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Posts: 3
Reply with quote  #1 
Hi All,
Just acquired a solar panel from the flea market & new to all this.
Tested it under direct sunlight at around 1400 hrs(i live at the equator).The results are
1. Voc - 18.67 volts(Tilted panel to get highest reading)
2. Isc - 3.67(Highest reading)
The panel size is 120cm x 54cm x 3cm(Thickness)
It looks like a mono crystalline type from the colour & the sticker had been peeled off,so there's no idea of the correct reading that i should be having.

There are 9 cells which looks like its corroded with age/water?
I had tried to cover those cells which are 'corroded' and it didn't show any changes in the reading.
Can i still use that panel for any usable charging?Any idea of the wattage of this panel?
Attached are some photos which may help.
Any help on this is much appreciated.

Cheers,
noobynoob

Attached Images
jpeg IMG_20170708_201638.jpg (212.36 KB, 13 views)
jpeg IMG_20170708_201726.jpg (238.33 KB, 12 views)
jpeg IMG_20170708_201702.jpg (225.25 KB, 11 views)
jpeg IMG_20170708_201711.jpg (232.57 KB, 11 views)
jpeg IMG_20170708_201545.jpg (133.70 KB, 11 views)

stmbtwle

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Posts: 2,729
Reply with quote  #2 
Well, it's a "12v" panel, probably around 100w originally, judging from the dimensions.

Might be good for 50w now. I'd get a cheap 5-10amp charge controller from Ebay, hook it up and hope for the best.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
noobynoob

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Posts: 3
Reply with quote  #3 
Thanks for the info,looking at the controller should i go for those pwm or mppt?
Is the panel is supposed to read 21v above for the Voc even over overcast sky?
Will test it again tomorrow at noon to see whether it will give a different reading.
Any recommendation for a high rise installation,i stay in a 4 storey apartment.

Thanks in advance,
noobynoob
stmbtwle

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Posts: 2,729
Reply with quote  #4 
Considering the panel I'd get the cheapest PWM I could find.  MPPT is best when there is a big voltage difference between the panel and the battery. In this case it doesn't look like there is; I wouldn't spend the money on an iffy panel.

Yes you should get around 21Voc, but because of the dead cells you're not.  Not much you can do about it.

Can you hang it out a window?  I find aluminum flat bar from the hardware store good for making brackets.  If you design it right you could close the window on the bracket to hold it in place.



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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
noobynoob

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Posts: 3
Reply with quote  #5 
You are right stmbtwie, will get 1 of those cheap PWM.Will try to get a replacement with the seller.Today's sky overcast with clouds.Couldn't test it though.Although we have a lot of sunshine here,it rains as much as well.I read in one site that the hot temp will actually decrease the output of solar panels?Its always hot & humid here with temp in the 90s as being the norm.
Still a lot to learn about this.
Thanks a bunch.

noobynoob
Rick H Parker

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Posts: 742
Reply with quote  #6 
"Tested it under direct sunlight at around 1400 hrs(i live at the equator).The results are
1. Voc - 18.67 volts(Tilted panel to get highest reading)
2. Isc - 3.67(Highest reading)"

I cannot say what the maximum power of the panel is but, It is safe to say maximum power is 70 watts or less. Because Voc is the maximum voltage the panel can produce and Isc is the maximum current the panel can produce. 18.67V * 3.67A = 68W, The maximum power I-V point is somewhere on the power curve between Voc and Isc.


You could try different loads, measure the current and voltage, calculate the power for each load. graph the power curve. From the graph you could get an Idea what the maximum power is.

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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
stmbtwle

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Reply with quote  #7 
Yes, high temperature does reduce your output. Mount your panel so there is good ventilation behind it. Not a lot else you can do.

I tried fan-cooling once. It helped, but the fan used up most of the gain, so I figure it was a wash.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
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