How does one check amperage on Solar panels NOT connected to batteries?

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djdenali
djdenali Registered Users Posts: 11 ✭
in Solar Beginners Corner #1
G'day,

I am connecting 3 '12 Volt' panels in parallel. When I check Voltage I read about 19.-- volts. Great. Right? When I check amperage, after swapping the black test lead into the negative (COM) jack, I get a reading of zero. I don't understand "remove power from the circuit under test, then open up the circuit at the point where you wish to measure the current." Is it possible to check amperage with them just being wired, sitting in the sun?

thanks.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #2
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    Re: How does one check amperage on Solar panels NOT connected to batteries?
    djdenali wrote: »
    I am connecting 3 '12 Volt' panels in parallel. When I check Voltage I read about 19.-- volts. Great. Right? When I check amperage, after swapping the black test lead into the negative (COM) jack, I get a reading of zero. I don't understand "remove power from the circuit under test, then open up the circuit at the point where you wish to measure the current." Is it possible to check amperage with them just being wired, sitting in the sun?

    When you use your voltmeter to check voltage, it has very high resistance and does not act as a load (which would pull down the voltage being measured).

    When you use it as an ammeter, it has very low resistance and you put it in the circuit so that all the amps in the circuit runs through it. It will have limits that you cannot exceed without damaging it, typically 10 amps.

    No harm will occur to your panels if you short them out, so the way to measure their maximum current is to short them out through the ammeter. Make sure your panel specs do not exceed the amp limit of your ammeter. To find out if your panels are producing at spec, you need to have them in full mid-day sun.

    For measuring amps it is desirable to have a DC clamp ammeter. No need to break any connections and insert a conventional ammeter, and the current limits are much higher than the typical 10 amps of a regular voltmeter/ammeter.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • djdenali
    djdenali Registered Users Posts: 11 ✭
    #3
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    Re: How does one check amperage on Solar panels NOT connected to batteries?

    Forgive my being unfamiliar with all the terminology and techniques. Is it possible to use the same meter I use for checking the Volts? If so, how so?
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #4
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    Re: How does one check amperage on Solar panels NOT connected to batteries?
    djdenali wrote: »
    Forgive my being unfamiliar with all the terminology and techniques. Is it possible to use the same meter I use for checking the Volts? If so, how so?

    What do you have for a meter? Make, model, or better yet, web site?
    There are thousands and thousands of different meters on the market, and without knowing your meter, it's really impossible to answer your question.
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    #5
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    Re: How does one check amperage on Solar panels NOT connected to batteries?

    On most general purpose (cheap) DVM's you don't move the black ground connection. You move the red probe lead from the Volt/ohm/mA banana jack position to the red 10 amp banana jack on the left hand side of the black common jack.

    The 10 amp jack has a short thick wire connected between the red 10 amp jack and the black ground jack. This short wire, internal to the meter, is adjusted to provide a reasonably accurate low value resistor. If lowest DC sensitivity of the meter is 200 mVdc then the wire is approximately 0.2v / 10 amps = 0.02 ohms. So much for the tech details.

    The most important thing TO NOT FORGET is to move the red probe back to volt/ohms jack before you try to read your battery voltage. If you forget there will be a pop and some smoke from your meter from the short piece of wire in the meter, providing the 0.02 ohm resistor, going 'poof'. There is typically no fuse protection on this since it requires low resistance for the amperage measurement.
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  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    #6
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    Re: How does one check amperage on Solar panels NOT connected to batteries?

    That's the very first thing I did with my multimeter checking panels - poof! Merely swung the rotary switch without disconnecting panel, moving jumpers properly, and then reconnecting panel. POP. Luckily it was fused, but at first was astounded that I somehow had a "bad" panel putting out no current. :)
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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #7
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    Re: How does one check amperage on Solar panels NOT connected to batteries?

    And if you doing this and want to avoid damaging the silver plating on the mc4s, dont test at the mc4s directly. Do it at the breaker or use a spare mc4 pigtail, or otherwise connect a pigtail lead to the mc4, and test acorss the pigtail, not the mc4. 35-45 volts in enough to generate an arc.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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