Solar panels with no specs??

Inferno · April 2013

Hi there,

I recently acquired a bunch of solar panels that don't have the model number or output info on the label on the back. The label is there but the wattage and output spots are left blank. Even the model number space is left blank.

Is there a way to get this info without knowing the model number? I got them from a bankruptcy so I have no resource to ask from the source.

The only info I can provide at this time is they appear solid black, are about 4X5 feet, and the voltage output read 156V on the quick test with a cheap voltmeter.

Any ideas?

Cariboocoot · April 2013

Re: Solar panels with no specs??

Welcome to the forum.

There's a couple of things you can test which will give you approximate figures. One of these is Voltage open circuit (Voc) which you've sort of done and got 156. That is enormous Voltage, and a bit suspect. Makes me wonder how many possible connections are there to them? Sometimes you have access to too any bits of the circuit and get a series reading of two segments where in normal application they'd be hooked in parallel.

Nevertheless, the other reading would be Isc: current at short circuit. Since this is an unknown value panel, it needs to be check with a DC clamp-on Ammeter. Short the two output leads together, place panel in direct full sun, check the current flowing through the leads (it won't hurt it).

Now actual power rating would be Vmp * Imp, so you have to 'fudge" Voc and Isc readings a bit to get a more accurate power rating. If that Voc is right it probably needs to go down 48 Volts to be near Vmp. The Isc will probably not be large either: perhaps 3 Amps? And it would be adjusted downwards about 0.5 Amps to be Imp. Then Wattage (approximate) is Vmp * Imp.

I'll guess these are amorphous, thin film, possibly flexible panels?
Any more info you can give us, especially pictures, and someone here might recognize them.

Inferno · April 2013

Re: Solar panels with no specs??

I wouldn't say they are flexible. They have a glass front and are pretty light weight though.

Here is a picture of one of them.

Attachment not found.

The person standing next to it, holding it, is 5'10"

Thanks for the help

BB. · April 2013

Re: Solar panels with no specs??

My first guess would be Dupont 100 watt amorphous solar panels:

Model
DA100-A1

Power (W)
100 Watts

Open Circuit Voltage (V)
99.29 Voc

Short Circuit Current (A)
1.55 Isc

Maximum Power Voltage (V)
76.96 Vmp

Maximum Power Current (A)
1.30 Imp

Dimensions (in)(LxWxD)
55.47" x 43.70" x 1.38"

Weight (lb)
44 lb

Connector
MC-3

The Voc voltage sounds high--Should be closer to 100 VDC...

One question, did you measure the panel voltage on VAC Scale (instead of VDC)?

-Bill

Inferno · April 2013

Re: Solar panels with no specs??

Heh, I may be a noob to solar panels but even this old noob knows that the sun doesn't output AC. I measured DC.
I measured the panel both with a direct sun and a 30 degree angle. Direct was 156 and the angle was closer to 143 (it varied because my buddy couldn't hold still).
100 watts? That seems like a small output for such a large panel but it could be right.

If it is a 100W panel then it's not worth much, right?

BB. · April 2013

Re: Solar panels with no specs??

Not attacking your electrical/solar knowledge... Just trying to figure out the Voc voltage that I have never heard of before. A meter set to VAC (sqrt(2)=1.41 conversion) would be one way.

Outside temperature of -40C/F would also be another--But did not look like -40 weather in your photograph. But I am from California--What do I know.

Setting up your DMM to 10 amp full scale and shorting the output with the DMM would tell you Isc (which is probably in the range of 1.55 Amps in full noon-time equivalent sun).

-Bill

Inferno · April 2013

Re: Solar panels with no specs??

No worries. It actually does make sense with how you showed the math. I was using someone elses VM so it's "possible" that I screwed up.

OK, so the next thing. I'm unfamiliar with the terms you are using. As I said, I'm a noob.

DMM=Digital Multi Meter
VAC=Volts Alternating Current
Voc=?
Isc=?
Vmp=?
Imp=?

Please fill in the blanks with noobspeak. I am a really quick learner, I swear.

No, it wasn't -40C/F. It was a 50ish day. ~LOL~

OK, so today I bought a clamp on meter. I've never played with one before but it's my understanding, by reading here, that all I need to do is clamp on a shorted wire and it will tell me the current? Is that correct?

Thanks for all your help

BB. · April 2013

Re: Solar panels with no specs??

Inferno wrote: »

DMM=Digital Multi Meter
VAC=Volts Alternating Current
Voc=? Voltage Open Circuit (panel voltage with no loads)
Isc=? Short Circuit Current in full noon-day sun
Vmp=? Voltage Maximum Power (a bit lower than Voc)
Imp=? Voltage Maximum Power (a bit lower than Isc)

Please fill in the blanks with noobspeak. I am a really quick learner, I swear.

Not a problem. We are here to learn and have a little fun.

OK, so today I bought a clamp on meter. I've never played with one before but it's my understanding, by reading here, that all I need to do is clamp on a shorted wire and it will tell me the current? Is that correct?

Make sure it is an AC/DC rated clamp meter--The more common ones (and usually less expensive) are the AC only clamp meters.

Yep--Point the panel to the ground (or cover with cardboard, etc.), connect the +/- solar panel leads together, and then put the DC clamp meter over the cable and point at sun. (solar panels are "special", do not short batteries).

-Bill

PS: DC current can sustain arcs better than AC--And connectors (MC4 type, etc.) on the cable ends can be damaged by the arcs.

niel · April 2013

Re: Solar panels with no specs??

looks like it may be in the 40-50w class judging by the size of it. if you get about 156v then you can roughly figure the short circuit current to be around the area of 50/156=.32a or 320ma or 40/156=.26a or 260ma. no big currents here because of the higher voltages.

vtmaps · April 2013

Re: Solar panels with no specs??

Inferno wrote: »

I measured the panel both with a direct sun and a 30 degree angle. Direct was 156 and the angle was closer to 143 (it varied because my buddy couldn't hold still).

I don't think the Voc shouldn't change that much when you change the angle, at least for any of the panels I know about. --vtMaps

Inferno · April 2013

Re: Solar panels with no specs??

niel wrote: »

looks like it may be in the 40-50w class judging by the size of it. if you get about 156v then you can roughly figure the short circuit current to be around the area of 50/156=.32a or 320ma or 40/156=.26a or 260ma. no big currents here because of the higher voltages.

OK, now this is where I get confused.
It makes sense that they would be a lower wattage with a higher voltage. Alternately it makes sense that a lower voltage would be a higher wattage for the same size panel.

So, having said all that, it appears people want to know Wattage ONLY, and value a panel based on that.
Does this make these $60 panels because they only have (let's say) 50 watts? Or does the higher voltage offset the low value of the wattage?

Cariboocoot · April 2013

Re: Solar panels with no specs??

Inferno wrote: »

OK, now this is where I get confused.
It makes sense that they would be a lower wattage with a higher voltage. Alternately it makes sense that a lower voltage would be a higher wattage for the same size panel.

No, Watts is the power. Volts * Amps = Watts. So higher Voltage panels tend to produce lower Amps but have roughly the same Watts. What you're really looking at here is the difference in panel efficiency, wherein it takes a much larger (physically) amorphous panel to produce the same power as a poly or mono crystaline panel (due to lower efficiency).

So, having said all that, it appears people want to know Wattage ONLY, and value a panel based on that.
Does this make these $60 panels because they only have (let's say) 50 watts? Or does the higher voltage offset the low value of the wattage?

Price per Watt is a very basic determination of panel value, but that alone can indeed get you in trouble. For instance people see 'bargain' panels, then find out the Vmp is too low and they won't charge their 24 Volt system without running two in series on a more expensive MPPT type controller. You are looking at the opposite problem here, with panel Vmp that will be quite high and yet can still cause controller problems. For instance the Voc of 156 you're seeing is too high for most MPPT controllers!

Inferno · April 2013

Re: Solar panels with no specs??

OK, so now I'm more confused. ~LOL~

I guess the basic question here is "what might these panels sell for?"

And I think it's safe to assume that I measured the Voc incorrectly. I will check again this weekend and see if I can find more info on all the three different panel versions I have.

BB. · April 2013

Re: Solar panels with no specs??

Right now??? Brand new, perhaps some sort of warranty, plus shipping--Maybe $0.50 to $1.50 per Watt retail.

The other issue is that "small" panels (less than 100 watts) can for $3 a watt new...

How much is it worth to somebody... If they already have some of these panels and want to add to their array and/or replace some damaged panels, probably well north of $1 per watt.

Somebody looking for project panels, probably well less than $0.50 a watt... The voltage on these panels is relatively high and non-standard. Either somebody would have to have a need for high(er) voltage panels, or they would have to buy a MPPT charge controller for $500-$600+ -- Not exactly a deal here.

But--I am not in the business and I don't sell stuff--So, it will probably be you finding a willing buyer that eventually sets the price.

I was looking around to see if anyone is selling Dupont panels (eh... not sure), but I did find a list of Dupont panels and they have some ~145 Voc panels here:

[TH="class: leftCol"] Manufacturer [/TH]
[TH="class: leftCol"] ModelNo [/TH]
[TH] Watts (w) [/TH]
[TH] Efficiency (%) [/TH]
[TH]Voc (V)[/TH]
[TH]Isc (A)[/TH]
[TH]Vmp (V)[/TH]
[TH]Imp (A)[/TH]
[TH]Tolerance
(%)[/TH]
[TH] Weight (kg) [/TH]
[TH]Weight (lbs)[/TH]

DuPont Apollo
DA127-C
127
8.12
149.3
1.24
122.8
1.0
-5.0~5.0
20.0
44.1

DuPont Apollo
DA130
130
8.31
125.0
1.03
152.0
1.3
-3.0~3.0
20.0
44.1

DuPont Apollo
DA130-C
130
8.31
154.0
1.27
118.0
1.1
-5.0~5.0
20.0
44.1

DuPont Apollo
DA130-C1
130
8.31
152.0
1.26
125.0
1.0
-5.0~5.0
20.0
44.1

DuPont Apollo
DA130-D
130
8.37
154.0
1.27
118.0
1.1
-5.0~5.0
30.0
66.1

DuPont Apollo
DA133-C
133
8.50
154.0
1.31
119.0
1.1
-5.0~5.0
20.0
44.1

So, yours may be in the 120 to 130 watt range...

-Bill

PS: I have to make a second post--The full table is too large...

BB. · April 2013

Re: Solar panels with no specs??

Here is the second part of the relevant table:

DuPont Apollo
DA133-D
133
8.56
154.0
1.31
119.0
1.1
-5.0~5.0
30.0
66.1

DuPont Apollo
DA136-C
136
8.70
155.0
1.35
120.0
1.1
-5.0~5.0
20.0
44.1

DuPont Apollo
DA136-D
136
8.75
155.0
1.35
120.0
1.1
-5.0~5.0
30.0
66.1

DuPont Apollo
DA139-C
139
8.89
156.0
1.39
120.0
1.2
-5.0~5.0
20.0
44.1

DuPont Apollo
DA139-D
139
8.94
156.0
1.39
120.0
1.2
-5.0~5.0
30.0
66.1

DuPont Apollo
DA142-C
142
9.08
156.0
1.43
121.0
1.2
-5.0~5.0
20.0
44.1

DuPont Apollo
DA142-D
142
9.14
156.0
1.43
121.0
1.2
-5.0~5.0
30.0
66.1

DuPont Apollo
DA145-C
145
9.27
157.0
1.47
122.0
1.2
-5.0~5.0
20.0
44.1

DuPont Apollo
DA145-D
145
9.33
157.0
1.47
122.0
1.2
-5.0~5.0
30.0
66.1

I don't know if Dupont Hong Kong is still in the solar business or not--Their website is acting pretty flaky for me right now.

-Bill

Inferno · April 2013

Re: Solar panels with no specs??

Thanks. This is helping me a lot. You have me wondering if I didn't accidentally measure with the AC setting instead of the DC.

The other people who were buying panels at the bankruptcy were paying $100 per panel. I wish I could get their info. ~LOL~

niel · April 2013

Re: Solar panels with no specs??

you might be right about the wattage range bill as i looked at the dimensions listed for the dupont pvs. maybe inferno can verify the dimensions on his. if they are higher wattage then that's a + for him.

you are right bill that anybody using these pvs will not get off cheaply as he would not only need an mppt cc, but probably at least an mppt like the classic200 and the pvs would all need to be in parallel mandating a fuse or breaker for each pv.

if they are higher wattage then the current will be higher proportionately. remember watts = volts x current. you cannot determine the imp from the voc and pv wattage just to be clear as the current is going to be higher due to the fact the vmp is lower than the voc. i'm probably further confusing him with that so i'll shut up.

BB. · April 2013

Re: Solar panels with no specs??

More than likely... I am wrong on the AC measurements... The "inexpensive" AC meter would measure the peak and divide by the sqrt(2)--So, sorry, I made a mistake there.

I am guessing that you have measured the voltage roughly correctly. And, I don't know if all of the above panels are the ~same size, and it is improvement in design/mfg/chemistry that increased wattage--Or simply bigger panel. It looks like it was an improvement in efficiency--So, other than making electrical measurements (and having no solar references handy/precision meters/temperature control), the lack of model numbers sort of leaves you in the dark as the the specific model(s) you may have. The differences are small enough to be pretty much meaningless in the over all system design.

Note that Amorphous panels do degrade over their first few (to six) months. So it is possible that the voltages will read 10-20% (???) high (and the panels will produce more power than the data sheet) until they "burn in".

Regarding paying more than things are worth at auction--That happens everywhere. My friend, a retired machinist sees people paying more than retail for used equipment... It is a combination of "auction fever", ignoring the auction fees+taxes, and sometimes people needing a machine now rather than waiting months (or longer) for a new one from the factory.

-Bill

BB. · April 2013

Re: Solar panels with no specs??

Niel,

If I remember correctly, Dupont panels had a series fuse rating of something like 15 amps (none of the data sheets I could find listed the fuse rating)--So, they were one of the few panels that could parallel more than 2 panels without needing a series fuse.

-Bill

Photowhit · April 2013

Re: Solar panels with no specs??

If your just looking for the retail 'new' value, I believe the low end of thin film is around 40 cents a watt, I think by the size(4x5') these are likely around 70-100 watt panels, thin film runs around 6-7% efficient. compared to around 14-15% for crystalline panels. I have some 14% panels that are about 68 inches by 38 inches. 200 watts.

Also note that thin film tend to start with a higher voltage during the first few months and reduce by around 20% over this time.

The target market for thin film is difficult as well, since they require more wiring, since the high voltage allows for fewer or only 1 per string so each must be fused.

Sorry I wrote this 4 hours ago at work, just got home and posted, looks like the mods have been tracking things down... I'll leave it though it doesn't add much if anything. We've got some great mods here!

Inferno · April 2013

Re: Solar panels with no specs??

Oh CARP!

If the measurement is accurate at 156V then the MPPT (whatever that means) will be hella expensive.
So, my best bet, in that scenario, would be to find someone who has the same panels installed with room to grow.

Of course, with the price I'm willing to sell these panels the extra cost of the MPPT (again, whatever that means) will be less significant.

I'm not loving solar. It's complicated.

Of course, if I owned my property, it'd be silly for me to not buy a controller and use them.

Inferno · April 2013

Re: Solar panels with no specs??

BB. wrote: »

More than likely... I am wrong on the AC measurements... The "inexpensive" AC meter would measure the peak and divide by the sqrt(2)--So, sorry, I made a mistake there.

I am guessing that you have measured the voltage roughly correctly. And, I don't know if all of the above panels are the ~same size, and it is improvement in design/mfg/chemistry that increased wattage--Or simply bigger panel. It looks like it was an improvement in efficiency--So, other than making electrical measurements (and having no solar references handy/precision meters/temperature control), the lack of model numbers sort of leaves you in the dark as the the specific model(s) you may have. The differences are small enough to be pretty much meaningless in the over all system design.

Note that Amorphous panels do degrade over their first few (to six) months. So it is possible that the voltages will read 10-20% (???) high (and the panels will produce more power than the data sheet) until they "burn in".

Regarding paying more than things are worth at auction--That happens everywhere. My friend, a retired machinist sees people paying more than retail for used equipment... It is a combination of "auction fever", ignoring the auction fees+taxes, and sometimes people needing a machine now rather than waiting months (or longer) for a new one from the factory.

-Bill

Good info.

As for the auction fever thing... I could sell these panels for $25 each and still make money.

Photowhit · April 2013

Re: Solar panels with no specs??

MPPT - Multi Power Point Tracking, basically it takes the input voltage and current and out puts the current at the correct voltage and current to benefit your battery bank the most.

To elaborate on the extra wiring, since they already have such high voltage, they will need a fuse for each panel if more than 2 (or 3 if the higher fusing is correct) with lower voltage panels you can often string 4 panels together, so if you want 1600 watt array, and you have an option of using 12 - 120watt thin film panels each needing a fuse or breaker and wire to reach the 12 position combiner box, then a single set of wires to the charge controller, or you could use 2 strings of 3 - 240watt multi or poly crystalline panels and only need only combine the strings(no fuse of breaker) and run a single set of wire back to the charge controller simplifying the wiring quite a bit.

Thin film are for the most part on their way out due to the cost of silicon becoming very cheap, so the balance of system costs (all that wire and fuses or breakers) out weigh the costs of the panels. The only advantage that thin film has is somewhat better performance (per label watt) in extreme heat.

Photowhit · April 2013

Re: Solar panels with no specs??

Inferno wrote: »

Good info.

As for the auction fever thing... I could sell these panels for $25 each and still make money.

You should do fine! since at least one has voltage, likely it's not a disposal situation! You might not be aware, and I would hope they are well marked if it's true in this case, but some of the thin film panels use 'Cadmium' in them and are hazardous waste.

...anyone want to buy some used Dewalt pod batteries? untested....lol(I love that)

Blackcherry04 · April 2013

Re: Solar panels with no specs??

The biggest problem I'd have is the real estate they would take up for the watts available. For what you could sell them for who cares....

Inferno · April 2013

Re: Solar panels with no specs??

BUT....

Isn't it true that the number of watts, at a certain Amperage and voltage, would be bigger watts if the voltage were reduced?

BB. · April 2013

Re: Solar panels with no specs??

Look at the "curves" from one of the data sheets (A-series here; did not find a C-Series data sheet)...

Watts = Volts * Amps

At a certain voltage (Voc = Voltage open circuit), you have full solar panel voltage and no current flow. P=V*I=Voc*zero amps.

Similarly, if you have a dead short on the solar panel you get zero volts and Isc (current short circuit. Again, P=V*I=Zero volts * Isc

So, Pmax is that point in the IV curve of the solar panel, where the equation of V*I=Pmax... Those points are Vmp*Imp (at ~25C or 77F).

You see a I*V curve horizontal in blue that slopes down sharply on the right. The V*I curve (Power in red), rises to a peak, then drops off again--That peak is Pmp=Vmp*Imp.

-Bill

Inferno · April 2013

Re: Solar panels with no specs??

Is this available in English?

mike95490 · April 2013

Re: Solar panels with no specs??

Inferno wrote: »

Is this available in English?

You need to get edumacated in electricity, till then, it will all be greek. Sorry. You gots to have a basic understanding of the terms and relationships. Till then, it's like : this ball peen hammer sucks, no way will it pull nails.

BB. · April 2013

Re: Solar panels with no specs??

Yea, the best way to explain the Pmp/Vmp/Imp curves is math...

If you look at the graph of Voltage vs Current and at each point along the VI graph get an XX volts at Y amps... (at 0 amps and 22 volts, then at 1 amp and 19 volts, 2 amps at 18.5 volts --- 7 amps at 17.5 volts and 7.5 amps at 6 volts, finally 8 amps at 0 volts--these are made up numbers).

Then for each V,I point, multiply those to give you ZZ Watts at each point.

Finally take that set points (power @ I amps) and graph that--You get the "red" power line.

If you are familiar with gasoline engines (motor in automobile). You have Torque VS RPM graphs... If you have ever look at those graphs, the point of maximum torque is not the same point as maximum horse power (HP = Torque*RPM).

Attachment not found.

Pretty much the same thing for solar panels... There is an optimum Voltage*Current point for Watts (Power) produced.

The reason that this may seem strange for you is that, in normal day to day life, the average non-electrical/electronic engineer works with Battery Based power sources... Or technically "Voltage Sources". Such devices (lead acid battery, your AC utility power) holds its output voltage pretty "flat" from 0 to its maximum rated current (until you pop a fuse or collapse the voltage source).

Solar panels (many times called solar "batteries" in older literature) are not "Voltage Sources"... They are (more or less) current sources... If you look at the V*I curve, you see the output voltage is pretty flat from I=zero to I=Imp amps (at that point, drawing more current causes the output voltage to collapse to zero volts and zero watts).

Voltage source - Wikipedia, the free encyclopedia
Current source - Wikipedia, the free encyclopedia

It turns out in electronics that Current Sources have all sorts of very neat properties that make such sources just as important as voltage sources for electronic circuit designs. And with the creation of transistors and integrated circuits, current sources are used "everywhere".

-Bill

Cariboocoot · April 2013

Re: Solar panels with no specs??

Inferno wrote: »

BUT....

Isn't it true that the number of watts, at a certain Amperage and voltage, would be bigger watts if the voltage were reduced?

No.
Watts = Volts * Amps. Reduce either Volts or Amps without increasing the other proportionally and Watts goes down.

There are, for example, some panels that can be wired in either 12 or 24 Volt configuration. When set for 12 the Amps is 2X that of when they are set for 24 so the Watts remains the same. (Basically they are two 12 Volt segments that can be internally connected either in series for higher Voltage or parallel for higher current).

Outside of that, panels are a current source and they will try to produce their maximum current under full illumination regardless of the resistance placed on their output; primarily the Voltage will change. The actual performance curve is along the lines of: Isc @ 0 Volts to Imp @ Vmp to 0 Amps @ Voc.

You may be thinking of what happens when you connect high Voltage panels through an MPPT charge controller to batteries: the controller will down-convert the higher Voltage to suitable levels for the batteries and at the same time cause an increase in the available current. The Watts remains roughly the same on the input and output. So you may have an array at 60 Volts and 10 Amps (600 Watts) going to a "24 Volt" battery system through an MPPT controller with the output at 30 Volts and 20 Amps.

Yes, I know: still Greek.

Solar panels with no specs??

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