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  • How to Test Solar Panel Voc & Isc

    OK time for another Sticky Topic that comes up a lot.

    WARNINGS
    • DO NOT ATTEMPT UNLESS YOU COMPLETELY UNDERSTAND THE MATERIAL PRESENTED HERE.
    • ONLY TEST 1 ONE SINGLE PANEL AT A TIME
    • DO NOT TEST PANELS WITH ISC RATINGS MORE THAN 10 AMPS OR MORE THAN 90 VOLTS VOC



    I TAKE NO RESPONSIBILITY FOR IGNORANCE. DO SO AT YOUR OWN RISK OF LIFE AND PROPERTY.

    OK now that we are very clear reading further is at your own risk let's move on how to properly test a single Mono or Poly panel. THIS DOES NOT APPLY TO THIN FILM PANELS. What is shown is a typical 36 cell battery panel. Same procedure applies to grid tied panels up to 72 cells. Only Test one panel at a time completely disconnected from every thing.

    Equipment Needed:

    1. A good quality Digital Multi-Meter capable of measuring DC Voltage up to 100 volts, and 10 amps DC. Most any DMM's can do this. Take note and read the instruction manual carefully as you have to move the test leads to measure VOLTAGE AND CURRENT. Make Damn Sure you understand how to configure the meter to Read AMP & VOLTS. It will require you to move the Red Meter Lead From Volts to Amps. Common is just that, Common to both measurements.

    2. A good Insulated Pair of test leads with Alligator Clips.

    3 Panel Voc and Isc Spec

    Test Conditions:

    1. Bright sunny condition around noon with panel facing directly into the sun. This is critical for the Isc Measurement. Otherwise you wil get low reading. Get your fat butt shadow off the panel.

    2. Use the Buddy system like your wife or friend who can provide emergency help if needed like call an Ambulance for you Morons who try this without fully understanding directions.

    3. Fully Disconnect the panel Under Test from Everything electrical. You want it completely isolated. Laying it on the ground by itself away from the house is ideal as you cannot fall off the roof if electrocuted or set your house on fire.

    Procedure:

    Voc measurement:

    1. Configure DMM to read voltage and connect as shown for V measurement.
    2. Connect DMM to the panel output positive and nagative output leads as shown. Take care not to physically touch any exposed wire. Use insulated test leads. Otherwise you might receive a mild shock.
    3. Refer to panel specs for the panel Voc voltage. What is shown is a typical 36 cell Mono or Poly panel Voc should be around 22 volts for a 36 cell battery panel. 50, 64, and higher count cells will be higher. Thin Film does not apply here.
    4. If Voc meets spec, continue to Isc measurement as the test has passed. Otherwise you have a bad panel.
    5. Disconnect meter from panel

    Isc Measurement:

    1. Configure DMM to read DC current at 10 amps.
    2. Very Important make sure you have bright full sun at noon.
    3. Connect meter as shown.
    4. Pay attention to details, make sure your DMM is configured properly.
    5. Refer to panel specs and note Isc, and then compare to what you see on your meter. Current should be within 15% of Spec. The amount of sun light is directly proportional to the current.
    6. If current looks OK the test passed. Otherwise you have a bad panel.

    LAST WARNING

    MAKE DAMN SURE YOU KNOW WHAT YOU ARE DOING




    I apologize for strong language warnings, but trust me it is necessary to get your attention. I really do care about you and your safety. NAVY Officer Training made me do it.
    Last edited by SunEagle; 07-18-2017, 11:33 PM.
    MSEE, PE

  • #2
    Another great sticky....
    howsabout could we get this sticky moved over to the Equipment for solar electric systems section? Would make more sense than Installation for grid tie ... even tho it is technical solar talk.

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