Testing new panels? 8 of them.

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SolarLakeHouse2
SolarLakeHouse2 Registered Users Posts: 16 ✭✭
in Solar Beginners Corner #1
I would think a guy would want to test the output after receiving new panels..I'm getting extremely low output.. (according to my controller) in direct (adjustable) mid day summer sun..less than 1/5 the rated panel output..damm..ordered a fluke meter to confirm this..
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  • SolarLakeHouse2
    SolarLakeHouse2 Registered Users Posts: 16 ✭✭
    #2
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    With 2 of the 8 panels..
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #3
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    I'm surprised, are they name brand panels?

    I use to worry and check every panel as soon as it arrived, but after40 or so panels, mine and for some friends projects, I quit worrying about them. I realized I hadn't checked my current panels, 20 - 200 watt, before I installed them. after I had everything hooked up I check with a clamp meter current into and out of my charge controllers and everything was fine...

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Johann
    Johann Solar Expert Posts: 245 ✭✭✭
    #4
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    If you have the panels hooked up to your system and the batteries are full then your amps from your panels will be low. Amps will increase with batteries that are more discharged or with an heavier electrical load on the batteries.
    You can check the amps of each panel (not hooked up to your system) if your meter can handle the amps that the panel should put out.

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  • SolarLakeHouse2
    SolarLakeHouse2 Registered Users Posts: 16 ✭✭
    #5
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    Is there a process for checking a "uninstalled" new panel? Lay it in the sun,conect the amp meter to the wires?
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  • SolarLakeHouse2
    SolarLakeHouse2 Registered Users Posts: 16 ✭✭
    #6
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    And thanks for your input..new to this
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #7
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    SolarLakeHouse2 said:
    Is there a process for checking a "uninstalled" new panel? Lay it in the sun,conect the amp meter to the wires?
    That will allow you to know the Isc.  The other easy measurement is Voc.   If both Isc and Voc are good, that does not prove the panel is OK, but it will catch most problems.  It will not catch any open bypass diodes.

    Once panels are installed, many defects can be picked up by thermal imaging of the panels.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #8
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    You can check the Voc (voltage open circuit)--In anything from "weak" morning/evening direct sun (to noon time full sun), a solar panel will read approximately Voc rated voltage (roughly 20-21 volts for a 36 cell panel).

    Isc (short circuit current), you can read this by shorting the panel +/- lead together (cover with dark blanket or cardboard before connecting MC4 + to - leads together--You should avoid making/breaking MC4 connectors under load--The arcing can damage the connectors). And under full noon time sun, you will read Isc.

    Note that Isc is (to a pretty good approximation) the amount of solar energy available at that moment from the sun (angle of panel, how clear the air is, etc.).

    If you have two or more solar panels to measure at the same time, you can compare panel to panel (under same conditions). They should be very close to matching each other (I would expect to 10% or better match).

    You can use a standard DMM (digital multi-meter) set to 10 Amp full scale DC current (most solar panels have less than 10 amps Isc rating). Make sure you set DMM back to "voltage" before connecting to the battery bank (or you will "fry" your DMM and leads).

    Or, you can use a DC Current Clamp Meter (here is a "good enough" meter for our needs that is not very expensive--About $60 from Sears). A DC current clamp meter is much easier/safer to use than a standard current meter (you have to "open" a circuit and put the meter in-line with the wiring).

    Note that Isc and Voc measurements will find 80-90% of all problem panels. It will not catch "all failed panels" but should be "good enough" for your needs. The DC current clamp meter makes it easy to check each panel string for current output through charge controller (the "best" testing method").

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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