Buying used panels from some random guy on Craigslist.

[fromport]

What about summer?

Because i am in southern cali, temps are easily why higher that STC rating and thus I see less power.
But that is why I said in spring, goof sunny sky but not high temp yet, almost mimicking STC conditions I see/measure 140+ watts out of a 158 watt rated panel that is 20+ years old. Pretty good imo.

My 3 yr old Talesun 330W panels rarely perform to STC spec because STC spec rarely happens in the real world. I get closer to 90%. My panels are at 6500 ft, in the AZ high desert, so they actually get more than 1000W/m^2, and they experience more mild ambient temperatures than Phoenix, but 90's are pretty common.
My best performance is in the colder months where panel tilt is not as favorable, but the notable cold boosts Vmp. I've seen 110% in those conditions.

Nice, I assume the high altitude lowers your ambient tempconsiderably?

Thankyou for taking the time to explain this.
185w kinda sucks lol I may just spend the money with santan solar on some of their used panels. They seem to be more reputable. Or maybe I’ll bite the bullet on new panels. I just don’t know where I can purchase 5-6 opposed to a pallet

No matter what kind of panels you buy, you will only get 80% of the rated wattage IRL.
That is because when there is a lot of sun the ambient temperature gets warmer than 25C/77F.
A new solar panels de-rates the most in the first few years, after that it slows down and becomes a steady percentage of like 0.1%/year.

If you don't need the higher watts/sq surface (not on roof van/rv), I would definitely advise to go with used solar panels.
They will last a lot longer than you think. Can't beat the bang for the buck. Some models of sharp panels had de-laminating problems with the film at the back but that was mostly with 160-180 watt panels. $70 each for 230 watt is $0.30/watt. You should try and get that down to $0.20 so I would offer him $45 per panel.

 

[sunshine_eggo]

Because i am in southern cali, temps are easily why higher that STC rating and thus I see less power.
But that is why I said in spring, goof sunny sky but not high temp yet, almost mimicking STC conditions I see/measure 140+ watts out of a 158 watt rated panel that is 20+ years old. Pretty good imo.

that's impressive.

Nice, I assume the high altitude lowers your ambient tempconsiderably?

It's still high desert. 15-20°F cooler than Phoenix. Deliciously dry. 30-40°F swings daily due to low humidity, so even the 90-100°F days rapidly collapse to 60-70°F most of the time. Monsoons muck that up a bit, but the higher humidity also lowers the peak temps.

 

[BlueMarblePA]

Multimeter is fused at 10amps!

This is valuable information as well. Thankyou.

I checked my used panels with my fluke multimeter in full sun and got appropriate open circuit voltage but zero amps. It is fused at 10amps, so I guess this makes sense. I remember when I bought them, his multimeter was showing appropriate amperage.

 

[Hedges]

?
Do you know how to measure amps with your multimeter?
Of course you can't measure Voc and Isc with the same configuration.

It is useful to measure Vmp & Imp, or V(load) and I(load). That can show defects not seen by Voc and Isc.

 

[chrisski]

I checked my used panels with my fluke multimeter in full sun and got appropriate open circuit voltage but zero amps. It is fused at 10amps, so I guess this makes sense. I remember when I bought them, his multimeter was showing appropriate amperage.

When my multimeter showed 0 amps on a good panel, my fuse was blown. The two multimeters I have, the fuse blows at 10 amps.

 

[Rocketman]

For a purchase like this could you just bring a half full battery connected to a mppt SCC, then plug in the panel, flip it over and see what watts it delivers.

Or am I missing something- wouldn’t that be easier?

 

[houseofancients]

For a purchase like this could you just bring a half full battery connected to a mppt SCC, then plug in the panel, flip it over and see what watts it delivers.

Or am I missing something- wouldn’t that be easier?

or a simple panel tester ..

LCD Photovoltaic Panel Power Supplys Solar Panel Multimeter MPPT Tester EY800W | eBay

Model: EY800W. For example, when the power of the solar panel is 100W, it is refreshed every 5S, and when the power is 300W, it is refreshed every 15S. Display mode: LCD liquid crystal display. Over rated power protection.

www.ebay.com

https://m.aliexpress.us/item/3256803885751715.html?spm=a2g0n.productlist.0.0.adae6d00kidIUg&browser_id=f75a13d4e37240e19e4ccd9a1f989cad&aff_trace_key=acd3576007804b8cb1a199d3635284a6-1665429472557-06794-_Atq3b7&aff_platform=msite&m_page_id=001183df8ac18f1aa1c03f02010111d89d256d66c7&gclid=&pdp_npi=2%40dis%21USD%2169.08%2146.97%21%21%21%21%21%400b0a187916659027714055548eefeb%2112000027944530513%21sea&curPageLogUid=tgbSJqQ3C7t9&algo_pvid=87ab45af-9a61-4b3a-9dd4-e7df254718d5

 

[BlueMarblePA]

?
Do you know how to measure amps with your multimeter?
Of course you can't measure Voc and Isc with the same configuration.

It is useful to measure Vmp & Imp, or V(load) and I(load). That can show defects not seen by Voc and Isc.

I switched the red lead from the voltage side to the amperage side. I must have a blown fuse. Will get replacement and retest.

 

[chrisski]

I switched the red lead from the voltage side to the amperage side. I must have a blown fuse. Will get replacement and retest.

I found that my cheaper multimeter rated for a 10 amp fuse actually blows at much less than that. I did purchase a DC clamp meter and now measure around 1 wire, and this is so much easier.

 

[OzSolar]

Just in case some folks don't know the method for quickly checking the fuse without having to take apart your VOM to get to the fuse. Here's the method illustrated by Fluke.

Side note: The post title conjured an image of a guy waiting for orders to come in then sneaking into the local farm under the cover of darkness to collect the panels he'd sold. Carry on...

 

[BlueMarblePA]

Just in case some folks don't know the method for quickly checking the fuse without having to take apart your VOM to get to the fuse. Here's the method illustrated by Fluke.

Side note: The post title conjured an image of a guy waiting for orders to come in then sneaking into the local farm under the cover of darkness to collect the panels he'd sold. Carry on...

This is helpful. I ended up taking out the fuse and then testing continuity -- no continuity. However, checking it without having to get the screwdriver out would have been helful. Thank you

 

[Mannfamilywoodworks]

For a purchase like this could you just bring a half full battery connected to a mppt SCC, then plug in the panel, flip it over and see what watts it delivers.

Or am I missing something- wouldn’t that be easier?

Sounds great. It would probably work. Easier? That’s such a difficult question. So many variables of so many systems. Some people panels might be 100’ up on a roof. Easier for some? Maybe. Easier for all. No.

 

[Alkaline]

get one of those meters that does both voltage and amps, Some used panels show good voltage but fall short of amps. Make sure it meets both.

I have had good success with used LG mono X panels, I paid $100 for 280 watt panels had a few years on them.

 

[Supervstech]

And use a can on the panel face, arrange so can has no shadow, and you are pointed at sun.