troubleshoiting help

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KhellSk
KhellSk Registered Users Posts: 91 ✭✭
in Solar Beginners Corner #1
48w 15.9v 3.02 now 3s3p 432w mppt50a
Used to be 9p pwm and was fine.

Battery died so i decided to upgrade.

I tested voc on each string and was fine but didnt test Asc because its been cloudy since. I test them individually 2years ago and was close enough to rated.

Today we had our first full sunny day in a while. But mppt reported
Yield 120wh
V mx 52
P max 59w

It seems like the only conclusion is that some panels are defective. What else could it be

_____________________________________________
[3p3s 48w 15.9Vmp] [Flooded 2x 6v 150ah]
[Victron 50/100 700wMax MPPT]







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  • BryceFreeman
    BryceFreeman Registered Users Posts: 27 ✭✭
    #2
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    For your 3s3p solar panel array Vmax 52v is ok but Pmax 59w is apparently too low. Since 59/52=1.1A, the amp is not normal. Yes some panels are defective, you'd better disconnect them from your system and test their voc and isc individually one by one to figure out which is faulty.

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  • KhellSk
    KhellSk Registered Users Posts: 91 ✭✭
    #3
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    BryceFreeman
    I had a 380wh yield, Pmax 191w today. Tree are blocking direct sunlight to my bottom row(1serie of 3) and were backed full of snow for the past week. I knew I had to relocate the panels but I thougth semi shaded wouldnt be as impactful with a mppt. 380wh in those conditions seems to me like panels might be okay after. What do you think @BryceFreeman ?
    _____________________________________________
    [3p3s 48w 15.9Vmp] [Flooded 2x 6v 150ah]
    [Victron 50/100 700wMax MPPT]







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  • BryceFreeman
    BryceFreeman Registered Users Posts: 27 ✭✭
    #4
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    KhellSk said:
    BryceFreeman
    I had a 380wh yield, Pmax 191w today. Tree are blocking direct sunlight to my bottom row(1serie of 3) and were backed full of snow for the past week. I knew I had to relocate the panels but I thougth semi shaded wouldnt be as impactful with a mppt. 380wh in those conditions seems to me like panels might be okay after. What do you think @BryceFreeman ?
    Ideally your solar panel array can produce up to 9*48w*4h=1728wh/day, so 380wh is far away from this expectation. Shades blocking any one of the panels will lead to power loss to the complete array, let alone you got 3 of them blocked. I think you should relocate the panels to remove any shades on them before you could do the test I said to figure out the faulty panels.

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  • KhellSk
    KhellSk Registered Users Posts: 91 ✭✭
    #5
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    @BryceFreeman @BB.  I built the scaffolding to go up check it out. So since voltage is fine, connections are fine, right ? I was thinking of test ISC of each series to see if I isolate where to look first. Do you guys have any suggestions on what I am supposed to look for ? I was thinking maybe the diodes are old

    Thanks in advance
    _____________________________________________
    [3p3s 48w 15.9Vmp] [Flooded 2x 6v 150ah]
    [Victron 50/100 700wMax MPPT]







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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #6
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    Any shading on a solar string will cut power a lot--Probably 50% of expected power (Watts) or more (depending on lots of things).

    Your 3x3 array... If the shading falls on "one series string" of solar panels, that string will be "out of service" while shaded (even if only one panel is shaded).

    If your shadows fall on one panel of each of the three series strings--That will also cut out a bunch of power... Again, at least 1/2--If this is a 48 volt battery bank, it could cut almost 100% of power (i.e., the array Vmp voltage is less than battery bank voltage). In your case, I believe you have a 12 VDC battery bank, so blocking one panel out of three on a string should still give you more than 15 volts to "charge" the battery bank.

    Anyway--The easiest way to to check a series/parallel array is to get a DC Current Clamp DMM (digital multi-meter). You can clip on each series string and directly measure the current and see if they are all roughly the same current, or if one or more strings is less--And you can focus on just the "weak" string(s). A couple of examples of DC Clamp meters (really AC+DC Current Clamp Meters):

    https://www.amazon.com/UNI-T-Digital-Handheld-Resistance-Capacitance/dp/B0188WD1NE (low cost--"good enough" for most debugging)
    https://www.amazon.com/Auto-Ranging-Resistance-Klein-Tools-CL800/dp/B019CY4FB4 (very nice mid-priced meter)

    If you have a "combiner" circuit breaker panel (i.e., 3 x circuit breakers in your case)--You can turn off one string at a time and monitor the current/power on your MPPT charge controller's panel.

    If you have a fuse based combiner box--Generally, it is not a good idea to "pop open" the fuse holder and they can arc and ruin the holder(s).

    At some point, your (presumably pretty old 48 Watt panels) are probably not worth saving--And you should look at new panels in the 120-200+ Watt range... Your old panels could have cost $10-$30+ per Watt... Today's panels can cost down towards $0.50 to $1.00 a Watt (plus shipping which may not be cheap). Or 3x 200 Watt panels for 600 Watt array at something like $600 worth of panels (as an example).

    Check the cells under glass on the panels--If you see cracked cells, browning/blackening of connections, corrosion from humidity, etc... That is usually not a good sign. And trying to replace the panel(s) is going to be difficult to find a "new 48 watt electrically similar panel).

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