[need help] pv output

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• Shawn-H Solar Expert Posts: 107 ✭✭

  November 2015 #2

  I need to know more about the components and what you have charge controllers load diversion devices things like that

  100% Off-grid in the White Mountains of Arizona. 36 Kyocera 265w mounted on four DPW 9 module pole top mounts, midnite solar combiners, breakers, & lightning arresters, 1 midnight solar classic 150, & 3 classic 150 lights, 3 x 1574 AH GB Industries forklift batteries total of 4722 AH @24v. Feeding a Outback power systems FW500 with 2 x VFX 3624, with the x240. 2 Honda EU3000is gensets with the 240 combiner and control box running LP, and 1 Honda EU2000is Gas. 
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• inetdog Solar Expert Posts: 3,123 ✭✭✭✭

  November 2015 edited November 2015 #3

  corazon said:

  halo, i'm new on this technology, i want to ask is it possible to find the output of pv module if its not connected to load?
  according to Pmax=Vm.Im or Pmax=Voc.Isc.FF
  from multimeter i can get the value of Voc and Isc but i'm stuck how to find the value of Vm and Im
  please help me, thanks before

  You cannot reliably tell the output of a PV module (cell or panel?) without a variable load. The only things you can measure are Voc and Isc. It is true that IF you know the fudge factor (FF?) for a particular cell design you can estimate the output as Voc x Isc x FF.
  
  As a rule of thumb for crystalline silicon cells Vmp is about 80% of Voc. The ratio between Isc and Imp will vary more widely.
  
  To actually measure Vmp and Imp you need to attach a variable resistance load and tune it to the Maximum Power Point before measuring. Or hook it up to an MPPT inverter or to a CC charging in Bulk mode into a depleted battery bank. And the whole time you need to use a calibrated reference light source or have the panels facing directly toward the noon sun on a clear day. Even in the latter case the panel temperature will be an uncontrolled variable.
  
  

  SMA SB 3000, old BP panels.
  

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• corazon Registered Users Posts: 2 ✭

  December 2015 #4

  thanks a lot @inetdog , i nearly understand,  so if  my panel not conected to any load (inverter, solar charge controller or variable resistance load), and i only measurimg the Voc and Isc with multimeter, i cant calculate Pout of my pv module (panel) right?
  btw what is the difference between Pmp and Pout? 
  
  
  

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• oil pan 4 Solar Expert Posts: 767 ✭✭✭✭

  December 2015 #5

  If you are only working with Voc times Isc you will get an unrealistic amount of wattage.

  Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

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• Dave Angelini Solar Expert Posts: 6,146 ✭✭✭✭✭

  December 2015 #6

  You should get a pretty close reading of power out with Isc.  Close enough for government work...

  "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
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• corazon Registered Users Posts: 2 ✭

  December 2015 #7

   
  
  from equation 5.12, i need value of Imp and Vmp to get the FF (fill factor) value.
  if i cant measure the Vmp or Imp since my PV panel not connected to any load, can i use eq 5.13 to get the FF? 
  
  thanks before

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