solar panel current

Discussion in 'General Electronics Chat' started by adamclark, Oct 8, 2013.

  1. adamclark

    Thread Starter Member

    Oct 4, 2013
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    I have a solar panel I got from a conversion van, it was used to charge an aux. battery for the tv and vcr in the van. Ive measured 16.8 volts from it in direct sun but there aren't any numbers or identification on it. all it says is solar power across the front, I have a blue point dmm with all the normal settings on it and I have a blue point mt599a scope that has all the normal dmm settings and a digital o-scope with a lot of other settings on it,, Ive only used it to set gains on my amps with the o-scope but it does a lot... What
    I need to know is how do I measure the max current this panel will make?
     
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Put a resistor between the points where you measured the voltage.
    This way you know the voltage, you know the resistance. Current=V/R.
     
  3. #12

    Expert

    Nov 30, 2010
    16,257
    6,757
    Know this, even if the sunlight is perfectly steady, the answer will not be a straight line. There is maximum no-load voltage, maximum current into a short, and all the places in between. 16.8 volts is a bit high for a 12 volt lead acid battery, but the voltage will load down as soon as it starts pushing current into the battery. Smile. It sounds like a pretty good match for the job.
     
  4. wmodavis

    Well-Known Member

    Oct 23, 2010
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    The two primary & easily measured specs of a PV panel are the open circuit voltage and the short circuit current. By simply connecting your DC ammeter across the panel terminals and noting the current under direct sunlight conditions you will have that Isc. Sounds like you already measured Voc. You could in addition plot a V-I curve and have additional info and then be able to determine the max power.
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    QFT. It sounds extreme to short out the panel (which is what the ammeter will do) but that is a normal and harmless test.
     
  6. adamclark

    Thread Starter Member

    Oct 4, 2013
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    so Just by putting my ammeter on it will short it to test the loaded voltage? or current? What size resistor? im a little new to measuring this kind of current ( in my field of mobile car audio/video we measure amperage with a clamp on ammeter on a car battery and measure the current under full system load, but I am talking high loads 100-350 amps, that's right amps, big 300 amp alternator and 50k watt systems.) Ive never had to measure anything in the low amps to Ma's,,, so what do I use to load this panel with to measure the amperage, and how do I do it with my dmm or o-scope? sorry,, Im positive that is a complete noob, beginner question,, how to use my own meter.. gosh.. I cant believe I actually have to ask that... anyway,, thanks...
     
  7. adamclark

    Thread Starter Member

    Oct 4, 2013
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    by the way the solar panel is 2" wide by 9.5 inchs long and has 18 row by 4 rows of 1.5x1 cm little cells...ive never seen one like this before.. normally when we put these on custom vans as trickle chargers for entertainment components we use a kit that has a 12" by 6" array that mounts on the roof and has its own charger circuit.. these are designed to keep voltage up on batteries of campers and stuff in storage for seasons.. but this is just a solar cell somebody had rigged up on their own, it seemed efficient tho,, the battery in the back had a 12.5 charge,, but the battery isolator that turns the cell off and lets the alt. charge the batt. was no good so we replaced it all with one of our systems and I just kept the solar cell to play with.
     
  8. wmodavis

    Well-Known Member

    Oct 23, 2010
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    .........................................
     
    Last edited: Oct 8, 2013
  9. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    The others are right, you don't really need the resistor.

    Basically right now you have an open circuit. You can measure the voltage because it is a field. But you can not measure the current because current needs a path.

    Take the ammeter (or multimeter set for current) and connect it to the two leads. What this does is completes the circuit. Now the current has a path and you can measure it.
     
  10. ronv

    AAC Fanatic!

    Nov 12, 2008
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    Maybe this will help.
    [​IMG]
     
  11. adamclark

    Thread Starter Member

    Oct 4, 2013
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    GOT IT..lol ,,, thanks guys,, results coming soon... this is just all new to me and I want to get it right..lol.. Ive got an idea I want to build with this panel and knowing the loaded/inloaded voltage and max amperage will be useful for my nuild thread here.. Ive came across a joule thief instructable that lights 3.8v LEDS from a single dead 1.5v AA battery.. I am intrigued by the circuit just because it steps up voltage to light a 3v LED from a dead 1.5v batt... Im currently working on a quadrotor project with my 12yr old son, and its coming along well with a 7 channel radio controller and receiver designed for RC aircraft... But eventually we want to use a microcontroller circuit to control it via gps and Bluetooth from an android device to give it military like "programmable mission" control so it can fly missions on its own and do whatever its sent there to do and come home on its own... Theres already plenty of arduino code and gps shields and gyrometer and accelerator shields to control it via Bluetooth or gps... sounds cool huh?? theres a few guys on arduino boards that are willing to help code it and I hope I can learn enough ( and in a timely manor) to build the circuit and keep it small enough to be weight sufficient to work,, right now the drone can lift 7 lbs. 100 feet in the air, and its batteries (4v L-ion baterries series/paralleled) can give it a 15 minute flight time.. The batteries are the first mod we did to the drone,, the rc batts. that came with the kit sucked and ive actually gained altitude and run time with my batt. setup,, I plan on doubling the batt. array to in theory keep the volyage the same and double the current, the power cell only weighs just under 3 ounces and we have a 7lb. payload, so it should actually help flight time signifigently....
     
  12. wmodavis

    Well-Known Member

    Oct 23, 2010
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    Just a thought here.
    I have found your posts to be a bit of a struggle to read through because of your writing style. That is - not using proper punctuation, capitalization etc. You might look at others posts and how they write. A big part of electronics IMO is clear and precise communication. I believe it is important. Your first post in this thread was good then you seemed to add periods and commas and not capitalize and it became harder to decipher. Just my thoughts.

    Hope your PV project works out.
     
  13. adamclark

    Thread Starter Member

    Oct 4, 2013
    472
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    oh I forgot my point in self absorbing gloat ?( im really proud of the advances in my drone) ,, but I was thinking of using the joule thief circuit modified with this solar cell to help keep a constant charge on the batteries in the drone to increase the flight time to as long as I can get. (I really would like to see a couple hour flight time, this coupled with gps control with an automatic return home failsafe would be awesome..) I don't have access to the power cells the gov. has to keep theirs in the air for days.. and the stuff that's close to it, I don't want to mortgage the house to buy,,, this is a hobby/project... The wife wouldn't let me put those kind of funds into a "toy"..lol
     
  14. adamclark

    Thread Starter Member

    Oct 4, 2013
    472
    6
    Ill work on that. I can be proper. Anything important I try to be clear and concise. But I do tend to ramble through the "not so important " stuff. I apologize.
     
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