diy solar

diy solar

Results of testing new panels from Santan Solar

RollingThunder said:
Hello everyone,
I just received my panels, 250w T series snail trails, from Santan Solar. The package was undamaged, and I tested the panels immediately after unpacking. It was between 11am-noon, sunny, hot, about 100f degrees. I tested one panel at a time, laid flat on some unistrut, on a concrete pad, so each panel was set on the exact same place, one swapped out with the next as quickly as I could do so. I tested each parameter for only 10-15 seconds before moving on to the next due to the very hot conditions.

According to the sticker:
The panel model is ss250p-60.
The VOC is 37.6v
The IMP is 8.27.

Test results of all 9 panels:
1. 34.4v,8.5a (292w)
2. 34.4, 8.49 (292)
3. 35, 8.55 (299)
4. 34.7, 8.6 (298)
5. 34.5, 8.55 (295)
6. 35, 8.6 (301)
7. 34.3, 8.7 (298)
8. 34.9, 8.69 (303)
9. 34.5, 8.73 (301)

These are my first solar panels, and the numbers seem good to me, can others validate that these are good to go?

Thanks!
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I assume you're measuring the open circuit voltage & short circuit current. The product of these values will always be higher than max power value (Imp*Vmp). However, Voc and Vmp track each other in a 1-1 manner. So, if the Voc of a used panel is X% below the nameplate spec, you can confidentially assume that the Vmp will also be X%of specified Vmp; the same goes for Isc & Imp. The ratio of Vmp*Imp and Voc*Isc is called the fill factor and this is usually 80-85%.

Since the panels were hot during your measurement, you have to account for that in Voc. However, Isc is not affected by panel temperature. If the measured Isc is close to spec'd Isc, then the panels are in good condition.
 
fat_old_sun said:
I assume you're measuring the open circuit voltage & short circuit current. The product of these values will always be higher than max power value (Imp*Vmp). However, Voc and Vmp track each other in a 1-1 manner. So, if the Voc of a used panel is X% below the nameplate spec, you can confidentially assume that the Vmp will also be X%of specified Vmp; the same goes for Isc & Imp. The ratio of Vmp*Imp and Voc*Isc is called the fill factor and this is usually 80-85%.

Since the panels were hot during your measurement, you have to account for that in Voc. However, Isc is not affected by panel temperature. If the measured Isc is close to spec'd Isc, then the panels are in good condition.
Click to expand...
Isc goes up with temperature. The Isc temperature coefficient of my latest pallet of panels is 0.05%/C.
 
JayArr said:
Holy Crap! - There's a club! Can I join?
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:)
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I bought 4 SanTan-Solar panels 3 months ago (BOGO) and installed them (1S4P) only this week with an AIO Eco-worthy 3000W inverter and 24V battery system (two identical ones in series). I have the panels in good location, no shadow etc. But even during midmorning with full sun shine, I am getting negligible amount of power. My Voc = 33.4 and the V op vol = 32.9 and my inverter charge light keeps blinking (I just have some 100W average load on this system now). The charge controller spec is 30 to 100V, so configuration is fine. My connections are hopefully fine (I am a retired ECE Prof.). Can any testing be done on the panel itself (as my inverter is new and no error codes)? What is the small box on the back of the panel and can that be opened? Are their any tech literature on them (even if for another manufacturer)? I notice some of you measuring short circuit current. Are you just connecting the multimeter in Amp mode and testing? Would it not ruin the meter?
 
Dr._Prof_ECECS said:
I bought 4 SanTan-Solar panels 3 months ago (BOGO) and installed them (1S4P) only this week with an AIO Eco-worthy 3000W inverter and 24V battery system (two identical ones in series). I have the panels in good location, no shadow etc. But even during midmorning with full sun shine, I am getting negligible amount of power. My Voc = 33.4 and the V op vol = 32.9 and my inverter charge light keeps blinking (I just have some 100W average load on this system now). The charge controller spec is 30 to 100V, so configuration is fine. My connections are hopefully fine (I am a retired ECE Prof.). Can any testing be done on the panel itself (as my inverter is new and no error codes)? What is the small box on the back of the panel and can that be opened? Are their any tech literature on them (even if for another manufacturer)? I notice some of you measuring short circuit current. Are you just connecting the multimeter in Amp mode and testing? Would it not ruin the meter?
Click to expand...
I'd recommend you rewire 2s2p, I bet you see a drastic improvement in performance.
Are your batteries fully charged?
 
Also don’t confuse VOC with VMP, those panels will prob be at 20-28v to reach name plate, this is well under what is needed to charge a 24v battery.
 
42OhmsPA said:
I'd recommend you rewire 2s2p, I bet you see a drastic improvement in performance.
Are your batteries fully charged?
Click to expand...
Thanks @42OhmsPA and @740GLE . After my post, I pondered on the issues, read more on MPPT and realized keeping the PV voltage much higher than the max battery voltage is necessary to harness the power. So, rewired my panels to 2S2P and tested with few loads (my storage of only 2x12.8x100 = 2560 is not enough to consume the peak power generated). With a small electric oven at 350 degrees F, I got little north of 800 watts for 4 panels. Not bad for a BYGO (@ $50) panels. Now I need to rearrange my electricity usage activities to consume power in real time (I am in a temp. rental house and the south was on the back kitchen side and going to distribute to two extensions on both sides for cooking use!).
Thanks once again.
 
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