sun energy Testing PV solar cells, How to use a multimeter


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This is just touching the very basics of testing your solar cells or solar panel for volts and amps.


The way of checking and testing your cells open circuit voltage (Voc) is by using a VOM, or multimeter. 

Some have an amp setting at 10 amp peak and some 20 amp. The pictures I show below is a common multimeter.

I took close up pictures so you can see exactly what is going on. Normally I test all my cells or panels with the 10

amp setting.  You can use the Milli amp setting, if you need to read in Milli amps with the 200m, 20m or 2m

settings 1000 ma is 1 amp so if your sell is only .20  amps  that would be 200 ma and so on.  Your multimeter is

only good for 10 or 20 amps.  To read volts is as follows;  Below is a picture to show the setting to test your cells or

panels.  if your panel is more than 20 volts, you will need to put the dial on the 200 volt setting. 



     
                                                                   Testing DC Open Volts









                                                                     Testing Short Circuit Amps






Voltage and Solar Panels

Solar Panels have three different voltage ratings that is helpful to understand. 

  • Nominal Voltage: The nominal voltage of a panel which is also known as the “conversational voltage.”  Nominal voltage refers to the voltage of the battery that the panel is best rated to charge. The actual voltage output of the panel changes as lighting and temperature conditions change, so there’s never one specific voltage at which the panel operates. Nominal voltage allows you to make sure the panel is compatible with the system you are building. 

  • Voltage at Maximum Power or Vmp: This is the highest voltage the panel can produce while connected to a system and operating at peak efficiency. 

  • Open Circuit Voltage or Voc: This is the maximum voltage that the panel can produce when not connected to an electrical circuit or system. Voc can be measured with a meter directly contacting the panel’s terminals or the ends of its built-in cables. You would expect to see this number listed on a solar panels specification sheet and sticker.

 You can refere to the chart below to find the open voltage VOC values for different types of solar panels, this gives you an idea of how much VOC voltage you would need to have the VMP voltage maximum value for charging. This is why you need more that 12 volts VOC to charge a 12 volt battery.

Nominal Voltage

VOC - typical

VMP - typical

# of cells in series

12

21

17

36

18

30

24

48

18

33

26

54

18

36

29

60

24

42

35

72





WARNING - DO NOT TRY TO TEST YOUR CAR BATTERY FOR AMPS, YOU COULD HURT YOURSELF AND DAMAGE THE METER. 12 VOLT BATTERIES CAN HAVE THOUSANDS OF AMPS.  SO PLEASE BE CAREFUL!  VOLTS IS OK JUST MAKE SURE YOU HAVE THE SETTING CORRECT ON THE METER.


 
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