testing short circuit current

[Mike90250]

I wonder what the problem is, I have made a simulation in Multisim of a whole PV panel with short circuit. Maybe I have overlooked something.

Hmm.. Multisim is supposed to use Spice , did you use a stock PV module, or did you use one you built yourself ?

[avandalen]

That's true for a "stiff" current or voltage source. It is not true for a solar panel. At all.

I wonder what the problem is, I have made a simulation in Multisim of a whole PV panel with short circuit. Maybe I have overlooked something.

[greenHouse]

That's true for a "stiff" current or voltage source. It is not true for a solar panel. At all.

[avandalen]

Solar cells are current sources.
Voltage sources like to be left open and wired in series. Current sources, on the other hand, like to be short circuit and wired parallel. See here an image which explains current sources.



It is safe to do a short circuit test on one or more solar cells in order to test the short circuit current.

http://www.avdweb.nl/index.php

[john p]

This all seems like a happy ending to this thread,, now just got to add a few hundred more magnets to my magnetron generator, and free power forever.. I read the book on how this all works,, you can get it too.. it only $49.50 But seems expensive paper to start a campfire.???

and no it wasnt bought with my money,thats why its more fun to work somewhere where they will buy such books.

[Sunking]

i have a clear grasp on ohms law, which is why i went off when people want to put 0 in the equation. am doing real world testing and have real resistance measured, real millivolts measured across that resistance and real amps.

IMHO that is where you got hung up and sidetracked in theory and classroom lecture. That is why academics teach they cannot do real work and make real things, they are too hung up on theory and cannot get outside that box. In this case you got hung up on ZERO ohms because it did not work in equations, rather than the resistance is so small and can be ignored and considered ZERO for practical purposes. That was what I was trying to impress on you.

When working with micro voltages and resistance it takes some very special test equipment very few have access too. In this application it is not needed.

Good Luck

SK

[RifRaf]

julie you are correct, i was more concerned to find cells that the tabbing wire was barely attached to (these were factory tabbed cells, and yes surely some were rejects) finding these is a big concern because i can understand that the entire 8A needs to flow freely between each cell and its tabbing wire. luckily the bad tabbing wire is less than 1 in 50, but that means it must be found for a string of 110 cells to function correctly

[greenHouse]

RifRaf,

Small amounts of missing semiconductor aren't as much a problem as any defect that affects the traces that "gather" the electrons from the semiconductor material itself. Remember that many photodetectors are in the square millimeter size range and manage to produce the typical 0.6 volts open circuit by however many milliamps of area there is.

Before I dropped a pile of money on a real pyranometer, I was testing pyranometers I made myself from 1cm x 2cm slices of monocrystalline solar cell.

[RifRaf]

The Isc test will give the same exact result if everything is working correctly.

exactly, and what i am looking for is the string that may not be working correctly. the rest of that post was correct and well explained

am testing mainly to see if the small chips that may be missing or the small corner missing are making a big difference, i won't deny that when making a diy panel the cell quality could vary, and as you mentioned the hairline cracks are there in cases, and some even can happen durin encapsulation, for this reason am encapsulating the diodes after the cells in order to leave test points before complete sealing, the testing of the majority of these cells shows they are up to the manufacturers specs

[greenHouse]

That is odd as he claimed in another post he was trained as an EE but moved on to other things.

Rule #1:

Julie has no grasp of sarcasm or other forms of humor.

Rule #2:

When Julie doesn't grasp sarcasm or humor, she will KEEP ON EXPLAINING whatever it is she's explaining until people explain that it was sarcasm and/or humor.

[greenHouse]

it does appear that my sarcasm was lost

Ah, that would do it.

Yeah, my Sarcasm Detector has been on the fritz for a while.

[russ]

im outa here for today,, have a magnetic generator to build just using magnets.. it will power my whole house,, then going to make my hydrogen generator to power my cars later today,, so no more buying diesel..

If you do everything today tomorrow is going to be boring.

[RifRaf]

indeed i have spent several years studying electronic engineering and many more with motor control, practical robotics and other electronic avenues, ohms law is one law that i do obey, it does appear that my sarcasm was lost, julie i have a clear grasp on ohms law, which is why i went off when people want to put 0 in the equation. am doing real world testing and have real resistance measured, real millivolts measured across that resistance and real amps. i understood from the second post in this thread the nature of solar cells being a current source and not voltage, so rather than be concerned with current draw as with usual circuits am more fascinated by the tiny voltages and resistances. i can't seen to get a simple point across so will give up trying, am happy with my current method of short circuit testing, am getting results i can use to eliminate bad cells or joints. if anyone in the future needs a hand to test the short circuit of cells can offer some practical advice.

[john p]

im outa here for today,, have a magnetic generator to build just using magnets.. it will power my whole house,, then going to make my hydrogen generator to power my cars later today,, so no more buying diesel..

[Sunking]

Yeah, but he's trying to grasp Ohm's Law

That is odd as he claimed in another post he was trained as an EE but moved on to other things.