testing short circuit current

[john p]

Mike despite you saying its BS and you cant make good crimps with vice grips on cables #4 and under and lugs 2mm thick.. Well you must have very weak little old ladies hands. We just read your post here at work and we all agree it can be done even if you cant manage it..We all here suggest you eat better energy producing foods.
Not even the electrical engineers here agree with you. And sorry despite it not working we are all going to continue doing it when out of the research and development workshop.... mabe you using cheap Chinese fake vice grips,, try buying the genuine USA made ones..

[russ]

Hi John, What you are describing is what I refer to as 'farmer engineering'. It used to have other descriptions but PC has eliminated most of them.

Farmers in the US, being generally of light skin color, have no such PC protection though so they have to suffer.

The proper tool for the task at hand is almost always better than using an adjustable spanner (crescent wrench) for hammer - or vice grips for a crimper.

[john p]

Russ yes mabe that is a good term, but lets stop and think about the first post. the person was asking about measuring the output of solar cells then somehow he got a reply all about not using solder for connectors and it was best if he spent hundreds of dollars an the correct tool..
But he did get one useless in the extreme reply to get some arc welding rods if he was going to be measuring the total of the solar panels output..
Now think about it is a person that is experimenting with home made solar panels ever likely to be making them so powerful that he is going to be suffering from melting connections?? and by some miricle having short circuits from soldered and crimped connectors?? well???? secondly you really think a person making home made panels is going to spend hundreds of dollars on the correct crimper??? thirdly is he likely to be going to try to get the panels certified and then connected to the grid?? hmmm I think not..
Call me farmer Joe if you like but I have used and so have many others used vicegrips to make crimped connectors. no matter how agricultural it seems if it works it works.. and vice grips do a far better job than a hammer.as using that the metal springs back a little so not good mechanical connection..

If anyone can show me a photo of the 2 wires coming out of a solar panel that had the connectors blow apart and the solder melt and then got short circuited because the connectors were crimped and soldered not using the correct crimper then I will become a believer
Mabe in Turkey every home handyman that makes solar panels has a power crimper to do crimp lugs on wiires.. Not so here in Australia

[RifRaf]

john p thanks for the reality check , was able to extract enough info from the comments to correctly measure short circuit current and successfully match up stings of cells and find issues. people insisting that anything times 0 = 0 is not practical though, learnt that in grade 2 or 3 i believe. while it is true, its also true that there will always be some resistance and therefore still a voltage, voltage will never equal 0 unless you guys have superconductors with 0 resistance for the test leads and connections between cells etc.

thanks for the help, shame it gets rather clouded with irrelevant info at times

[Sunking]

0 = 0 is not practical though, learnt that in grade 2 or 3 i believe. while it is true, its also true that there will always be some resistance and therefore still a voltage, voltage will never equal 0 unless you guys have superconductors with 0 resistance for the test leads and connections between cells etc.

thanks for the help, shame it gets rather clouded with irrelevant info at times

Of course wires have resistance and is the reason there is some voltage, but you missed the point of power = curruent x current x resistance = power. So if you have a 100 watt panel with a Vmp = 18 volts, IMP = 5.55 amps and Isc = 6 amps. If you take the Isc value of 6 amps and run it through .oo1 ohms of resistance in the wriring what is the power?

Could it be .036 watts? That is insignificant and close enough to zero to call it nothing compared to 100 watts. It is like comparing 36 cents to $100 right?

[john p]

solarpaneli great reply . But its meaning is?/


AH HA now i see the meaning..

1. Build a 100 Watt solar panel for as little as $125 or less. If you choose to purchase cracked or broken solar cells, you can further reduce that to $30! That's a $1040 savings per solar panel. If you decided to convert your whole home you could save $25,000 over the costs of having someone do it for you.

2. Build a wind turbine for as little as $100. The main design in our guide shows you how to build a 450 Watt turbine. To buy a similar turbine, the turbine alone will cost you $4,000. That doesn't include the mount, the installation costs, or the wiring. By the time you've built your turbine your savings can add up to $10,000 or more!

CRACKED OR BROKEN CELLS?/ GIVE CRACKED OR BROKEN OUTPUT.. VERY GOOD if you are also cracked or broken in the head
$100 for wind generator,, WOW .. built solely with items bought from your local hardware store??? and your turbine does not need to be mounted on anything?/? that saves money for sure. save even more with no wiring??

[russ]

He dumped two links to one of the '200 dollars and forget the power company forever' sites.

I told him he is welcome to participate but those links are not allowed.

Sometimes newbies don't realize what they are doing - usually such is from a dedicated spammer but not always.

Russ

[john p]

Russ he knew what he was doing selling impossible dreams to people.. you just cant make panels and wind generators that are good fot those prices.. not even for me "farmer joe"

[russ]

@ Farmer Joe (John) - I just try to give the benefit of doubt and keep a close eye to remove such posts as quick as possible.

Speaking of Farmer Joe, I grew up on a farm and remember the saying, ''It went haywire''. That meant wire from hay bales was used to try to hold something together on a temporary basis - usually not for more than 10 or 20 years.

What makes me laugh is when the scamsters and click bank types get upset over having links removed.

Russ

[john p]

Here in Australia we have same saying but the meaning and use slightly different.here it means something went very wrong. the other thing is here on farms fencing wire is the repair item of choice of just about everything and a good pair of pliers

[RifRaf]

Voltage = I x R, P = I x I x R. So if R = 0 then voltage and power have to = 0 because anything multiplied by 0 = 0

as i want to test the Is it appears i am surely doomed

Could it be .036 watts? That is insignificant and close enough to zero to call it nothing compared to 100 watts. It is like comparing 36 cents to $100 right?

er no it could not be, for a start i measure over 15 times sunkings values and therefore conclude the stupid 36c in $100 to be a stupid argument, if anyone cares can provide some actual measured values

[Mike90250]

If you are just measuring Isc, you don't care about power, you are measuring amps.

I'm not sure I understand what you are trying here. we don't care about power at this point, just measuring amps to see what the panel/cells can put out.

Open circuit volts is another useful measurement, but it also has nothing to do with power.

After you connect it to the battery, you can measure volts and amps and calculate power, that will be a real measurement.

[RifRaf]

all i want to do is measure the short circuit current, if we simplify the argument to Vs=0 then all testing is void, ohms law is broken and Is=0 because I=V/R an V and R are both 0, so there is no short circuit current, see how silly this gets and does not help any.

the voltage measured at Is does interest me, no matter if just a few mV, the resistance of the cells to tabbing wire, bus and tabbing wire, test leads and meter also matter no matter how small they may seem, there is a huge difference between, 0.001R and 0.020R, and neither is 0, an odd reading still indicates an issue like a bad solder joint or mistabbed broken cells, a point that will get hotter than other places and likely fail in the future.

am not really interested in power output, am interested in power losses due to a fault, so voltage and resistance are just as important as the current when testing short circuit current for these reasons

[Mike90250]

Voltage in a short circuit will never be = 0 unless you are using super conductors. The shunt in a meter has a set resistance, so the meter can read the calibrated voltage across it, and display the amps. Wire leads have resistance. internal tab wire = resistance, there is some everywhere, usually, less than an ohm.

Just measure it. there will be very little difference in AMPS if the wires total 0.002 or 0.008 ohm. (I'm assuming you are measuring a multi amp panel, if you are trying to measure milliamps of a chip off a cell, you will need some better gear.)

[RifRaf]

i don't get your point sorry, my test gear is fine for millivolts, amps and milliohms, it does not matter if i am testing a single cell, a string, 2 strings in parallel, a panel, an entire array or a chip from a cell, ohms law still applies exactly the same way.

personally if i was testing a set of cell strings and most had 0.002R calculated resistance and one had 0.008R i would be concerned, there will be a 4 fold increase of voltage drop across that string than the others, 4 times more power loss than the 0.002R string. in real testing the resistances appear to be higher than these numbers which makes it matter more.

please remember the whole point of testing is to ensure matched strings of cells to make the best functioning diy panel, am trying to find issues in order to fix them, not interested that a perfect cell has almost no voltage at maximum current, am trying to find the Not perfect ones