Solar Cell & Panel Short Circuit Current - How to measure

[HarisHashim]

I have 6" x 6" solar cell which was rated with 8A short  circuit current.

Initially I checked the short circuit current using multimeter (Black terminal to front of the cell [-ve] and Red 10A Max terminal to the back of the cell [+ve]). The current is about 0.4 to 0.5 A.

When I refer back to the sell seller, says something have to measure several cell instead of just one cell.

Today I have finally assemble something like 20 solar cell (5 by 4). And do the measurement (Black terminal to -ve and Red 10A Max terminal to +ve). The result is about the same 0.5A to 0.6A,

I don't expect it to be 8A, but 0.5A is simply too low. The voltage is fine at 10V plus.

What might cause this?

Thansk in advance!
 

[MagicValleyHPV]

You really need to monitor the voltage at the same time you apply the load - it should drop significantly. I loaded a 15w Harbor Freight module today, and the voltage dropped from 22 Voc down to 350 mV - the amperage measured slightly below 1 amp (hazy weather conditions). 

[Opera House]

"I have 6" x 6" solar cell which was rated with 8A short  circuit current..........The voltage is fine at 10V plus."

Is this a single cell or a panel?   A single cell would likely see the voltage burden of the meter and leads and only produce that much and a single cell   would not put out 10V.  I agree with the seller, a neophyte would not be able to measure the current of a single cell.

[DanG]

Short circuit current test condition is exactly as stated industry wide. You have other problems especially if multiples read low.

I have 3x6 tabbed evergreen cells rated .55~V and 3 Amps I see 4.5 amps instantaneous (single cell) in my test jig before the 60 Watt halogen light sources heat begins dropping output from the wafer.

I made a quick jig to slide wafer in, fold over onto contact plate, light on, VOC test then ISC. If you want you could inject resistance and trim it so you read approximately the MPP spec voltage and cull low current output wafers at that voltage.

I had to try different combinations of digital meters and then ended up having to turn one on after the other was in circuit to correctly initialize both meters logic.

[ghurd]

Was the testing done indoors?

If you are not sure what you are doing,
they must be tested outside in the sun,
with good sun,
and no shadows on the cells.

G-

[HarisHashim]

... 4.5 amps instantaneous (single cell) in my test jig before the 60 Watt halogen light sources heat begins dropping output from the wafer.

I made a quick jig to slide wafer in, fold over onto contact plate, light on, VOC test then ISC. If you want you could inject resistance and trim it so you read approximately the MPP spec voltage and cull low current output wafers at that voltage.

I had to try different combinations of digital meters and then ended up having to turn one on after the other was in circuit to correctly initialize both meters logic.

DanG,

Sounds like there is a need for load (halogen light) to test short circuit current? Perhaps this is where I'm mistaken because I just touch single cell + and - to the multimeter?

I really need to know ho to check one cell. Is there a link where I can see how to construct the jig?

Ghurd,

My bad to do the test indoor ... I'll try to do it outdoor tomorrow. But I have tested 1 cell outdoor with about the same amperage result.

And I do test 1 cell = 0.5x v  get arround 0.5A

And then I test half a 20v panel = 10v get arround 0.5A to 0.6A. Possibly because being indoor.

[tecker]

It sounds like a meter problem see if the panel will bring up a car battery or some thing that needs an amperage of that range If you can chain up some auto lamps that would help you . What meter do you have ?

[tanner0441]

Hi

Need more information...  What is the rating of the panel? Voltage, wattage, and maximum rated output, not into a short, all your measuring when you connect a meter across the panel is the load the meter imposes on the panel.  10V at 8A is 80W.  80W from a six inch square panel is optimistic beyond belief.

Even if you are assembling a panel from six inch units you still need to know the individual panel ratings to know how many you need for the size unit you want to build.

I have 60W of panels that will put 3 to 4A via a charge controller into my batteries, 12V.

Brian

[Simen]

Nobody?

All solar panels/cells give max amps when directed directly towards the sun. if you cast a shadow over just part of one cell in a panel, the output are reduced significantly.

Test it outdoors and point the cells directly towards the sun.

[joestue]

believe it or not those cheap meters have a lead resistance of nearly half an ohm or more.

if you want to measure 8 amps accurately you will need a calibrated 1 milliohm resistor.
one foot of 10 gauge wire is an adequate substitute.

[deg15scorpio]

I have the exact same problem with a batch of 6x6 cells I bought off eBay.  Are the cells defective or am I defective? :-)   I have a 100 ohm resistor in series with a 6x6 cell in full sun out doors and only read 5.17mA on the 20mA setting on my digital multi meter.   The cell was culled to have short circuit current of 8amps.   

Any help appreciated!!!!!

[joestue]

(5.17 mA )*(100 ohms (plus 10 for your amp meter)) = 0.56 volts, approximatly the open circuit voltage.

if you want to actually measure 8 amps short circuit, you will need to short out the cell with just under 1 foot of 20 awg wire and you should read 0.08 volts across the wire. (the wire will warm up an that voltage will increase with time..)

[rain1224]

So many suggestions, are these work?



"link removed"
Please do NOT add links here that are advertisement!

[Watt]

So many suggestions, are these work?

Some do, some may not?  Which ones do you question?

[richhagen]

deg15scorpio, you cannot test the short circuit current through a 100 Ohm resistor.  The resistor will limit the current according to Ohm's law.  What I have done to sort cells, although probably not the best,  is to solder the front and back tabs on and to measure the current with a meter while aiming the cell unobstructed at the sun at about noon on a sunny day. 

In the past if I did not have a meter capable of making an accurate measurement,  I would have found a 1 percent tolerance resistor of about a tenth of an ohm in my parts box short that across the leads of the cell and measure the voltage across that.  I usually use test clips but I have some fairly thick ones.  The resistor would ideally have been rated at a Watt or so of power dissipation, as from Ohms law.  This would not be accurate for measuring the current, but I would expect the voltage to be at the cells max power voltage or higher across the resistor.  This was not really useful for determining the exact current, but was useful for batching cells of similar current together.

Joestue's method is much better, just short the segment of ten gauge wire across the cell and measure the voltage across the wire, again, with the cell in full sunlight - aimed at the sun at high noon.  If you have an approximately 1 milliohm resistor, you should see a voltage, from V = I*R, with the I at about 8 Amps, and the R at 1 milliOhm of .008V 

I just calculated that pure copper ten gauge solid wire should have a resistance of .00099993 Ohm's in a one foot length.  It should make a pretty good measuring tool for this purpose.  There is likely some variance in commercial wire, but it should be reasonably close and make a fairly accurate measurement.