# Brand new to solar!

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Hello all,
I have recently purchased 16 solar panels that are 3 foot wide by 4 foot tall. panels has 12 squares that measure 1 square foot each. I am not sure the brand of these solar panels or when they were manufactured. I am curious how to tell how much electricity they will produce. How can I tell if these are 6 volt or 12 volt panels? How do I know how many watts these panels produce. These panels are about 1 inch thick. Well the frame for the panels is 1 inch thick. The collector is much thinner. These solar panels came with a frame and a harness that connects them all. I am also unsure what kind of solar charge control I will need. The kinds of other questions I have I will probably have to find in a book. I'm not sure what kind of batteries I may need or how many if any at all. I'm sure I will need an inverter to convert to ac. I have a total of 192 square feet of solar panels. Also on the back of the collectors it looks as if there is paint or some sort of material that resembles paint. This material looks as if it is cracking from age. No damage to the collector. Would I need to cover the back of these collectors before I could use them. One more bit of info on these panels. Each panel is 4 squares tall by 3 squares wide. On the back of the collectors there is a positive and negative wire on each section of 3 squares. This means there are 4 connectors to each solar panel. I am not sure if this will give any clue to the brand or age of these panels. I didn't pay much for these and figured it would be the start of a long journey into the world of alt energy.
Bryan

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Re: Brand new to solar!

Place one of the panels in full sun and measure the open circuit voltage on each terminal set... For example, a "12 volt panel" may read 20-22 volts or so (depending on temperature and sun).

Next, put the panel in shade or cover with cardboard or lay upside down on the grass. Connect one set of terminals to a current meter (or a DVM set on 10 amp range). SLOWLY expose the panel to full sun (do it slowly to make sure that you don't exceed the amp meter's current rating and destroy the meter--the panel will be just fine if shorted). The full sun short circuit current will be close to the current rating of the panel.

You can look at a view manufacturer's specs. and see if you can find the Voc and Isc and estimate Vmpp and Impp (mp=Maximum Power Point) for you panels... As above, your Vmpt will probably be something like Voc*21v/17v=Vmpp and Impp=Isc (Isc and Impp are pretty close to the same for a solar panel)... The watt rating of the panel would be approximately equal to Vmp*Isc

Voc and Vmp are temperature dependent and would be most accurate if measured when the panel is cool (that would be the STC rating). The PTC rating would be if the Voc was measured with the panel warmed up on a warm day (Vmpp drops with temperature).

The above will not be a "lab quality" testing of your panel's rating--but is probably close enough for you to rough out a system design (within +/- 10% or so).

You can test each panel for Voc and Isc and quickly sort the good from the bad panels (you will need to test each terminal block, or three per panel--if I understand you correctly).

As far as fusing the panels (protect the array against short circuit)--you can probably place two panels (or strings) in series with out a fuse, otherwise, if you place more than two panels (or strings) in parallel, each string should be protected with a fuse that is rated at 1.25-2.0 * Isc.

No clue about the coating on the bottom...

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 10,300 ✭✭✭✭
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Re: Brand new to solar!

i find it unusual that somebody would purchase 16 pvs and not only not know if they are buying them at a good price, but would have no idea what brand they are or what they can do and how. you bought these blindly? what makes this even more strange is that the seller should know this stuff to tell you the buyer.
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Re: Brand new to solar!

and i thought that was a unique hobby of mine to blow my meters fuses all the time.
BB wrote:
you don't exceed the amp meter's current rating and destroy the meter
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Re: Brand new to solar!

I still have that box of extra fuses with my DVM that I bought for college several decades ago (minus a couple)...

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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Re: Brand new to solar!
niel wrote:
i find it unusual that somebody would purchase 16 pvs and not only not know if they are buying them at a good price, but would have no idea what brand they are or what they can do and how. you bought these blindly? what makes this even more strange is that the seller should know this stuff to tell you the buyer.

Hummmmm, I was thinking the same thing - - Tends to raises questions - - and red flags too.
Wayne
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Re: Brand new to solar!

while replacing a fuse i heard this box fall off the back of a truck , FULL of solar panels!
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Re: Brand new to solar!
mattl wrote:
while replacing a fuse i heard this box fall off the back of a truck , FULL of solar panels!

I wonder how hot they'll get under full sun? Will they need cooling fans?
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Re: Brand new to solar!

wink wink, ok we're going over the edge here :roll: (I cant believe *im* saying that) :-D
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Re: Brand new to solar!

I bought these solar panels from a nieghbor for 50.00 dollars. She is an older lady that was interested in installing them on her home and decided that they were being wasted in her shed. She could tell me nothing about them. Now I am Interested :-D Thanks for the replies I'm sure I will have a long way to go before I get them installed and working. I guess thats why I am here.
Thanks :-)
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Re: Brand new to solar!

Brian

50 bucks for the whole lot??? Are they new?

My friend, if they work, you may have scored a huge deal!!

Looks like BB offers some really good advise on identifying the output is. Hell, if nothing else you could build a dandy chicken coop.

I, for one, will be very curious how this turns out!!! Very curious!!!

Mike

PS

If these panels are good ones, You will have to change your handle to "Lifeisgood" or something like that!
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Re: Brand new to solar!

LOL
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Re: Brand new to solar!

I am no expert in old solar panels, but the ones you describe look like one I had a few years ago. They are 12V panels without the diodes, so you have to put diodes between the connectors before you put them all together (I think its enough just on the plus side,but I'm not sure, the experts here will surely know more). From the size and age (i say at least 25 years old if not older) they should give you between 40W and 60W for 12V, my old Kyocera from the 1980s produces a good 50 Watts at the same size.

In the worst case that would mean 600W of solarpower but if you are lucky you could look at close to a thousend.

The stuff peeling of the back is the waterproofing paint or silicone, you can just respray them and put some silicone around the frame to waterproof them.

For controlling them, you probably be best off putting them in 2 arrays for 24V and get a decent controller, something going in the 30A+ Range.

Before you start however test them all,one by one. You can put a simple voltmeter on each plus and minus and read the results (in full sun anything above 4V is good, 5V is better). If one of the lines of three is not showing anything, you can not use that panel as a hole but even so its still not worthless, one can do other things with it.

Your neighbor should now however where she got the panels from. Even if she knows nothing about them technically, she must have paid for them at one time and it was not \$50. She dropped a 0 or two there.

Greetings

Chris
• Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
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Re: Brand new to solar!

Bryan,

Take a look at the backside of one (or all) of the PV modules. There should be a label with the manufacturer's name, model number and the PV module's specs (Volts max power, or Vmp; Amps max power, or Imp; Volts open circuit, or Voc; and Amps short circuit, or Isc; all at STC). Bing this info back to us and see what we can do to help you out.

HTH,
Jim / crewzer
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Re: Brand new to solar!

Everyone,
Thanks for all of the helpful info. In the next couple of days I will try to find some sort of information on these panels and relay them to this forum. You guys seem to really know your stuff. I have spent alot of time on google and this is the only place thus far I have found anything. I did feel like I got a good deal on these panels even if all I do is build a chicken coup out of them:) lol. One of the panels had a cracked corner and the lady I bought them from acted as if she was ripping me off. I will take your advise and test them and I will relay the results as soon as I get the chance. Thanks and I really appreciate your help.
Bryan