Evaluating used Panels in the Northeast

[CitroM]

I am negotiating a purchase of 20 second hand (12yo) poly PV 200W panels. Is $50/panel a decent price? They are a local pickup for me.

Originasl Specs: Voc - 33.4v, Isc - 8.12A

I was able to test about half of the lot today, in full northeastern November sun, from about 1PM forward.

At some point the sun began to dip and became somewhat obstructed by a distant tall leafless tree. Still bright, but waning and the Volts mostly remained consistent, from panel to panel, dipping slightly from just over 32V to just under.

The Amps however began a steeper decline, from around 6.3 progressively lower to 5, 4, 3 etc. Here is the table:

(#1 is obviously damaged)

Panel Voc A(Isc) Time
1 12.7 5.97 1:00PM Bright Sun
2 32 6.24
3 33 6.28
4 32 6.47
5 32 6.35
6 32 6.47
7 31.4 5.8 2:00PM Dimming
8 32.3 4.8
9 31.8 3.9
10 31.8 3.6
11 31.5 1.75

Is this in line with normal panel performance?

--
Michael

 

[sunshine_eggo]

You're looking for outliers.

#1 looks like a horrible outlier unless there's a typo. 12.7Voc? bad panel for sure.

2-6 look pretty good.

I would re-test 4, 7-11. Compare 7-11 to #4. Discard outliers.

 

[CitroM]

I went back today to test the rest of the batch and retest the several with low values.

The results confirm what I suspected: in dimming sunshine (day1, 2PM and progressively later) the Amp output declines steeply and very fast.

On day2, today, the testing began at 11:30 (bright sunshine) and progressed for the next hour or so. Turns out the panels reach upwards of 90% and panels 8-11 are fine.

For $50 per 200W panel and no shipping I will call it good.

Thanks for your comments!

--
Michael

This table omits volts, which were all 32/33, except for #1, which I will not buy.

# Isc % of 8.12/label

1 5.97 73.52%
2 6.24 76.85%
3 6.28 77.34%
4 6.47 79.68%
5 6.35 78.20%
6 6.47 79.68%
7 5.8 71.43%
8 4.8 59.11% 7.45 91.75%
9 3.9 48.03% 7.46 91.87%
10 3.6 44.33% 7.5 92.36%
11 1.75 21.55% 7.6 93.60%
12 5.15 63.42%
13 6.01 74.01%
14 6.02 74.14%
15 7.54 92.86%
16 7.42 91.38%
17 6.8 83.74%
18 0.00%
19 7.25 89.29%
20 7.5 92.36%
21 7.3 89.90%