Solar panels on eBay

[peterh]

We have a nifty 13"x48" 50w solar panel on our Scamp's roof that fits nicely between the "headroom hump" that runs down the middle of the trailer and the housing for the retractable awning.



The panel is a Siemens/Shell/BP Solar (the company has been bought and sold a few times) SM-50 clone that we bought on eBay, and it works so well that I keep thinking it'd be nice to install a second panel on the other side that would pretty much guarantee we'd never run out of electricity. So now and then I check eBay, and there's a pair of similar panels up for sale right now, auction ending on Monday.

Alas, right now I have trailer projects up to my eyeballs and no time to add another panel, but since it's a frequently discussed topic here I thought I'd point them out. If they are as advertised (I don't know the buyer and haven't inspected the panels, so this is a shot in the dark of sorts), they'd be a good start for a do-it-yourself solar project. (I'd use a different controller than the one that comes with the panels, by the way.)

Used Shell Solar 50 watt solar panel with controller.

Used Shell Solar 55 watt solar panel with controller.

[Bob H]

Any concern over the "used" status of these panels? Do panels degrade over time? Is this the same guy you got yours from? ...geeze! Can you tell I'm interested?

ConwayBob

[Gina D.]

Yes, they do degrade over time. The lifespan shortens if they have been left out 100% of the time, but still.. I don't recal exactly. It's somewhere between 20-25 years average.

Linky about that

[Ricky 4]

We have a nifty 13"x48" 50w solar panel on our Scamp's roof that fits nicely between the "headroom hump" that runs down the middle of the trailer and the housing for the retractable awning.



The panel is a Siemens/Shell/BP Solar (the company has been bought and sold a few times) SM-50 clone that we bought on eBay, and it works so well that I keep thinking it'd be nice to install a second panel on the other side that would pretty much guarantee we'd never run out of electricity. So now and then I check eBay, and there's a pair of similar panels up for sale right now, auction ending on Monday.

Alas, right now I have trailer projects up to my eyeballs and no time to add another panel, but since it's a frequently discussed topic here I thought I'd point them out. If they are as advertised (I don't know the buyer and haven't inspected the panels, so this is a shot in the dark of sorts), they'd be a good start for a do-it-yourself solar project. (I'd use a different controller than the one that comes with the panels, by the way.)

Used Shell Solar 50 watt solar panel with controller.

Used Shell Solar 55 watt solar panel with controller.

Please give us more pictures -I am very interested.

[Gina D.]

These are not Peters panels for sale. He just pointed out the eBay sale.

Click on the links for more info.

[Roy in TO]

Please give us more pictures -I am very interested.

Just in case you are interested in Peter's install with more pictures here is the complete thread:
http://www.fiberglassrv.com/board/in...howtopic=25052

[peterh]

Any concern over the "used" status of these panels? Do panels degrade over time?

Assuming these are true TM50 and TM55 panels, no, I wouldn't worry. Monocrystalline and Polycrystalline solar cells, like those used to build the TM50 & 55, degrade slowly, loosing up to 20% of their rated capacity over the course of 30 years, so after 30 years of use a 50 watt panel will still pump out 40 watts. A similarly aged amorphous panels will produce less than half their original output. (Panels constructed of crystalline solar cells have a "postage stamp" appearance where cells are arranged in rows and wired together; amorphous cells typically have a single surface that looks like a solid coat of dull black paint.)

What you do need to look out for in used crystalline panels is damage due to storm damage, hail, and other impacts that can crack the cells. Take a good look at the pictures of the cells you make offers on and make sure any panel you buy on eBay comes from a guy who has good feedback on lots of sales and check his or her most recent feedback to make sure s/he hasn't gone downhill on his/her most recent sales. Only buy panels that the vendor claims to have tested and guarantees will work, then, when you get your cell, take it out and point it at the mid-day son and measure
1) its output voltage, which should be comfortably over 17 volts and
2) the amperage the panel delivers to a short circuit.

[b]Make sure you know how to use your multimeter and that it is rated for 10 amps, otherwise you will blow its internal fuse or fry the meter.

The panel's actual maximum output will be about 75-90% of the measured short-circuit amperage, and the output in watts is this reduced number of amps times your charging voltage, typically 14.5 volts. For a 50 watt panel you'll also need a solar panel controller or you'll boil your battery to death.

Is this the same guy you got yours from?

No. I have no experience with this particular seller, but I'm feeling very tempted . . .

[Bob H]

Peter,
Thanks for all the great information. I'm curious, how hard would it be to make a protective storage cover for your array installed on the roof, for when you are traveling, or when you are storing things for a season.

Is it necessary, or would it extend it's life over time?

[peterh]

Peter,
Thanks for all the great information. I'm curious, how hard would it be to make a protective storage cover for your array installed on the roof, for when you are traveling, or when you are storing things for a season.

Is it necessary, or would it extend it's life over time?

Let me break your question down into two parts: How might I protect my solar array from 1) impact damage and 2) degradation due to sun exposure when I'm not out using my trailer.

I don't worry much about protecting my panel from impact damage. Quality solar panels are built to withstand small to medium size hail and such, but not the kind of impacts one might see from large hail or extreme storms, and if my trailer was caught in such a storm I'd be worried a lot more about the rest of my trailer, not just the solar panel. Buying used from eBay is another matter: I'm sure there are people who sell damaged panels on the used market, which is why I was careful to buy from an eBay seller with a lot of sales and overwhelmingly positive feedback.

Because I have panels made up of monocrystalline cells that degrade very slowly I don't worry about wearing them out, end of story. If I had amorphous-construction panels (like the Harbor Freight panels and many others), which degrade very rapidly in the sun, I'd stow or cover them when I wasn't using my trailer.

One more comment. I do worry about dirt and dust, which won't damage the panel but will dim the sunlight hitting the panel. I pop my head through the escape hatch/vent and dust the thing off when I'm setting up to boondock.