Low amperage on 4-100w Renogy panels

dnpowers
dnpowers Registered Users Posts: 3 ✭
in General Solar Power Topics #1
Hello all. I had 4 renogy 100w panels running to a 30amp renogy charge controller. I started noticing a low battery situation so I started doing some tests. If I completely disconnect the panels from the system and check each panel individually I get between 19.5-20.5v on all 4 panels, but I am only seeing .18, .19, .21 & .31 amp from each panel. I ran my multimeter in line on both the + and - wires as well as introduced a load on the circuit with the same low amperage results. What happened or what am I doing wrong? Thanks for your help!
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  • NANOcontrol
    NANOcontrol Registered Users Posts: 261 ✭✭✭
    #2
    I imagine those panels are in parallel from those readings.  What is the array voltage at those currents. If over 18V the panels may be fine and the controller is not accepting more current, 
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  • dnpowers
    dnpowers Registered Users Posts: 3 ✭
    #3
    NANOcontrol said:
    I imagine those panels are in parallel from those readings.  What is the array voltage at those currents. If over 18V the panels may be fine and the controller is not accepting more current, 
    Those are the voltage readings I get from the individual panels not wired in parallel or series. I disconnected them from the whole solar system to test the voltage and amperage of each panel trying to get to the root of my problem. 
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #4
    What load(s) did you connect to the panel(s)?

    A quick test, is to set your meter to 10 Amp full scale DC current. And "short" the panel out with your meter. That would be "Isc" or short circuit current.

    The Isc measured is directly proportional to the amount of sunlight hitting the panel. Cool, clear, day, solar noon, panel pointed at sun will give highest value of Isc (normally, around 50% to 100% of Isc from spec. sheet).

    Since you have 4 panels--Measuring the Isc at the "same time, same sun"--They should match Isc pretty closely (within 10% or so)...

    Longer term, if you want to learn more about how your system works, and do some detailed debugging when needed--I would highly suggest an AC+DC Current Clamp DMM (digital mulit-meter). A couple to start your search:

    https://www.amazon.com/UNI-T-Digital-Handheld-Resistance-Capacitance/dp/B0188WD1NE (low costs. "good enough" for our needs)
    https://www.amazon.com/Auto-Ranging-Resistance-Klein-Tools-CL800/dp/B019CY4FB4 (mid price range meter)

    Just take the current clamp and clip around each panel lead to measure current under load (in circuit), or just short the panel leads together to measure Isc.

    If you have flooded cell lead acid batteries, a hydrometer of some sort is very helpful too:

    https://www.solar-electric.com/midnite-solar-battery-hydrometer.html
    https://www.amazon.com/s?k=battery+hydrometer&sprefix=battery+hydrom,aps,574 (get one with glass float)

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • dnpowers
    dnpowers Registered Users Posts: 3 ✭
    #5
    BB. said:
    What load(s) did you connect to the panel(s)?

    A quick test, is to set your meter to 10 Amp full scale DC current. And "short" the panel out with your meter. That would be "Isc" or short circuit current.

    The Isc measured is directly proportional to the amount of sunlight hitting the panel. Cool, clear, day, solar noon, panel pointed at sun will give highest value of Isc (normally, around 50% to 100% of Isc from spec. sheet).

    Since you have 4 panels--Measuring the Isc at the "same time, same sun"--They should match Isc pretty closely (within 10% or so)...

    Longer term, if you want to learn more about how your system works, and do some detailed debugging when needed--I would highly suggest an AC+DC Current Clamp DMM (digital mulit-meter). A couple to start your search:

    https://www.amazon.com/UNI-T-Digital-Handheld-Resistance-Capacitance/dp/B0188WD1NE (low costs. "good enough" for our needs)
    https://www.amazon.com/Auto-Ranging-Resistance-Klein-Tools-CL800/dp/B019CY4FB4 (mid price range meter)

    Just take the current clamp and clip around each panel lead to measure current under load (in circuit), or just short the panel leads together to measure Isc.

    If you have flooded cell lead acid batteries, a hydrometer of some sort is very helpful too:

    https://www.solar-electric.com/midnite-solar-battery-hydrometer.html
    https://www.amazon.com/s?k=battery+hydrometer&sprefix=battery+hydrom,aps,574 (get one with glass float)

    -Bill
    I did a short current test with a 10amp Klein meter and got those results. I tried to introduce a load onto the panel by powering a 12v spotlight to see if it would change those results and it did not. I then tested the same panels with a cheap Innova 10amp as well as a expensive fluke 374 clamp with the same results. 
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,044 ✭✭✭✭✭
    #6
    Probably a dumb question, but, are you moving the positive lead from your multimeter to the current testing port?

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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