Broken solar cells...

[zmoz]

I see that the guy selling the chipped solar cells on ebay by the pound that everybody loved so much has stopped. I would still like to build a panel from cheap broken cells, but most lots come with a whole bunch of very irregularly shaped peices. If I was to make a 12v panel with these, would there be a problem with wiring cells of different amperage in series? For example, if I had a bunch of peices that were all .5v, one 100ma, one 150ma, and one 200ma, could I wire them in series to get one 1.5v, 100ma panel? Or do they all need to produce the same current?

[Shadow]

The guy still had some on Ebay today, they are just alot more money now. 75.00 a pound.

[zmoz]

Got a link? I couldn't find any...

[DanG]

I'd really, really hate to win this auction.

http://tinyurl.com/cbv82

28 lbs of PV culls - $35 shipping.

Last bid $46; 5 days left in auction.

[Shadow]

Try this link,

 http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=3240&item=5969988242&rd=1

[pyrocasto]

zmoz, you're right,that would work fine as a panel. I'll make a diary about the process I found to put them together good. It's very easy and works fine. I'll post the link when I'm done.

[picmacmillan]

as far as i know the ebay guy (bryon) has some left, but as stated above, they have skyrocketed in price.......he did give me an offer that maybe still sticks, he said i could get a 50 pound box of unculled cells for 20 bucks a pound...he said i could even sort through them and pick all good ones if i wanted....these cells were just in the box as he receives them...maybe  a few people could get together and buy a 50 pound box...definately cheaper...just an idea pickster

[ghurd]

In less than a year, my wholesale cost of PVs using the same type of cell has gone up nearly $1 per watt.

G-

[scottsAI]

Warning Yes you can mix outputs, but understand what happens.

The panels output is limited to the weakest (lowest current) cell.

To over come this individual cells can be paralleled, so they output the same current as the rest of the panel. Then used in series as the rest of the panel.

Each cell should have the same surface area, irregular shapes are difficult to size, without measuring them. Measuring is tough, need same sun for each measurement.

Try weighting them, a 0.1 g resolution scale is $15 on ebay. (I got one:)

Each string of cells should have a reverse diode. Remember, the panels output is determined by the weakest cell, a bird flying over a panel can cause the output to drop. The string diodes prevent a large voltage reversal on a single cell.

I do not know the reverse voltage rating of a solar cell. Make sure it's not exceeded. This will determine how many cells to use in each string.

Have fun.

[zmoz]

That's interesting, picmacmillan. Would anybody else be interested in a group buy for these things?

[pyrocasto]

I would, but I was under the impression that he didnt have enough left to do that. He told me the same thing, but it was like a month ago. I would def. go in with ya'll if the offer is still up though. If it's not, I'll buy those broken pieces from the other guy on ebay. lbs are lbs, broken or not so I'll take either as long as I get the right price. :-)

[nothing to lose]

I might take a couple pounds if the deal was still good.

I wonder about that other guys deal on those broken ones, 28lbs for $48 I think was the bid when I looked. I might beware.

Questions at the bottom of the auction he said he got them from someplace .com and I went to that site. Phototvolatiac.com I think or something like that, it's on e-bay as part of his answer to a question, if this guy is connected to that site I would beware, if he just bought the cells like any other business deal then it may be ok.

Either that is a really one freaked out parranoid dude that put up that page/site, or I really pity him!

The page that loaded said the site was supposed to been for his solar pannels he designed which could be grown and spray painted onto about anything originally, but then went into all kinds of stuff about crooked cops, judges, Fbi Cia and others out to get him and shutting down his lab etc and stuff about all kinds of unbeleavable stuff he's supposedly been involved in. Judges sending hit men after him blah blah blah, like reading 5 years of National Enquirer all at one time. I did not read a whole lot of it.

Where did he ever have time to work on solar cells and panels if all that were true??

 I consider it to be similar to some-one explaining a crooked oil company burned down the magnetic motor plant they built to run cars on over-unity for feul.

 I certainly hope it was a bad april fools joke they forgot to take down!!

Anyway if the E-bay seller is just some guy doing business it may be a good deal, if he is connected to that site I think I'll stay away for now.

[Jeff7]

Wow, search on eBay for Solar Cells. Quite a few people reselling these cells, either just as-is, as "kits", or auctioning the broken pieces off. I bet Bryon could have sold these things for $50 per pound from the start and eventually sold them all off. I for one am very glad he sold them cheap.

Or at least I WOULD BE if I could find a source of Devcon Metal Welder, and get my panel project underway.

[lnxduk]

I just got a pound of cells for $65 (after shipping)  It seems like it wasn't a great deal now, but I am new to this.  The cells were "broken"  They are 3"x6" 1.5w each, and I have about 24 that are almost complete (minor chips), and another 16 or so that have 2 halves.  The rest are in worse shape, maybe I can make a nicad charger or something with them.  I can still use it if I have both halfs right?

Hopefully I should be able to get 36 pretty good working ones in series for a cell.  This in theory would be 54w,  would it be possible to get 30w?

I will constantly be monitoring the cells when in use, so would it make sense to make 3v cells, then put them in series/parallel arrangements depending on the time of day?  Or at least I can get the best ones in line.

Do I need a charge controller to charge a 30ah battery with these?  I am looking to spend $25 or less for one if I actually need it.

Can I get a charge controller that will boost the voltage, so I can give it basically any voltage 0-30, and get a nice 13.8 out?

What is the best way to mount these cells?  I can hopefully get large pieces of 1/4" glass, and glue is everywhere.

Do I really need the 2% silver solder and where can I get more ribbon to connect to the ends of the cells?  Anything ordinary I can substitute?

Some of the cells are a darker blue than others.  What does this mean?

Sorry I have so many questions, and thanks for any answers.

[ghurd]

Try to match the broken ones for size. You want 36 cells in series.

It would be good to check each for similar output. The PV output amps will be about the same as the lowest cell output (weakest link in the chain).

With a 50w PV and a 30ah battery it should have a controller unless you are going to baby sit them. Sealed batteries don't like much overcharge.  Around $25 can get a Morningstar SG-4 that will handle about 60w no problem.

MPPT Controllers are big bucks, so buy an extra factory 50w panel and parallel it with your homebrew panel instead. Cheaper and you will get more power!

You can built a simple very controller.

This link shows one. Be warned, the page is HUGE and full of photos.

But 2/3 of the way down is "Shunt 1", "Simple shunt charge controller".

Everything could be available at RadioShack?  Or any surplus electronics dealer much cheaper with a better selection.

http://www.redrok.com/electron.htm#led3x

Construction is covered all around this site.

G-

[lnxduk]

Hi, thanks for the info.  If I were to get a smaller commercial panel, say 3-5w, would it be possible to put them in parallel?  If I ran the larger one through a controller, and the smaller one to the battery with a diode (it is kind if weak to do damage) would this work?

Also, how effective is it to use packing tape and just tape the solar cells onto glass?  All this stuff about sealing without humidity and submersion in oil is kind of complicated.

My idea is to put the clear tape over the front of the cell, and maybe even use 2-3 layers of it, and attach it to glass behind it.  This would essentially seal the cell and make it weatherproof.  Or am I missing something.  Thanks.

[pyrocasto]

Well, sorry I didnt get a chance to make my diary. I've ran into a few complications.

But I wouldnt use tape if I were you. I would use a sign laminate, and you could use it on both sides as you want. I got the idea from fishfarm on this board, who made 4'x8' panels with this stuff, and I'm using it for the chiped panels. It's "ORACAL 651 SERIES 2.5 mil 5 YR HIGH GLOSS INTERMEDIATE FILM" and I ordered just 15"x50' for my application.

Here's his post on his setup: http://www.fieldlines.com/comments/2005/1/7/204547/8060/21#21

Here's the website I got mine from:

http://www.signsupplystore.com/ProductCart/pc/viewPrd.asp?idcategory=0&idproduct=4503

They didnt give me shipping or any emails before I recieved the product, so I was a little irritated. But it got here, and they sent me an extra letter with an extra reciept and details. It cost about $20 after shipping which is what I expected.

This is made for outdoors, unlike the packaging tape you mentioned.

[ghurd]

For a little more money than 5w PV, you can get a 10w. A little more than that, you get a 20w.  Keeps going like that until 50 or 75w.  You can get a good 50w PV for about 4 times what a good 5w costs.  Maybe $60 to $220, extra $160 well spent.

Its kind of hard to get a good 5w PV.

But yes, it should work OK with a 5w.

I wouldn't tape them together. Who knows the light transmission of packing tape? Plus it gets brittle and yellow fast, probably faster in the sun.

I kind of like the vented panel idea, if I was going to make one, which I am not.

(used to say that about windmills too. Now I'm butt deep in half finished mills!)

I do find it very interesting though!

I know I would not use any wood, anywhere.  Or epoxy.  Probably 2 layers of glass, silicone, and a proper fitting, heavy duty Al frame.

Why reinvent the wheel kind of idea.

Just 2 cents.  Except the tape thing- thats a dollar.

G-

[Jeff7]

Why no epoxy?

[ghurd]

Ever see that glass wall in the fancy restaurant (actually the little dividers at Denny's here) that look like cracked ice?  They are sealed in a double pane kind of deal.

They smear epoxy on the glass, it cures and shrinks (expands?), and pulls off the top layer of glass as it does.  They are sealed so nobody gets hurt on the rough edges.

Maybe it would be OK. I wouldn't want to put it to a time test with different thermal expansion properies, etc.

[pyrocasto]

But that's exactly what someone needs to do. Test it.

I will but right now I'm too busy/poor. ;-)

[lnxduk]

I put together a 15 cell panel from some of my cells.  I got it to do 8v open, and about 1.5 amps shorted, went a little above 2a for a split second when the sun came out a little more, but it was still sort of overcast.  I used the 1.5w cells.  The whole thing weighs about 10 pounds, because the glass has a heavy metal fram around both pieces.

I plan to make a second cell, and put both of them in series for charging a 12v battery.  I would assume they can provide 14v under load, and this should be able to charge a battery.

I will still have some leftover cells, but mostly smaller pieces.  I would like to connect them (make a 5w panel) but it is very hard to solder to the back of them, and a lot of the pieces don't have ribbon on the front either.  can I use aluminum tape instead?

Also, are there any charge controllers that would let me charge a 12v battery off this 8v cell?  I know how to build a device that would do it, but it is only 50-60% efficient.

thanks

[ghurd]

I think it would take a few years.

Or maybe a lab.

Heating and cooling cycles etc.

Some kind of semi flexable potting compound with a close thermal expansion rate would probably be a better investment than epoxy.

[Jeff7]

Concerning epoxy - I've been looking over a lot of documents at Devcon. Only a limited number of their epoxies will even adhere to glass at all, and their one technical document says "Glass bonds are not durable."

And just an overdue update on the other solar cell auction, linked here, it finally sold for $575.

[ghurd]

There was an outfit Downunder that made a kit.

Good efficiency if I recall.

Would charge 12v from about any voltage, or a broken PV.

They did a lot of experimenting with types of transistors and found one worked far better than any of the others.

I can't find it now.

Probably found it before looking for 'solar panel repair' or something close to that.

G-

[mongolei]

28 lbs of PV culls - $35 shipping.