Clamp meter indicates 4 of 18 panels are now defective after 4 1/2 years.

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softdown
softdown Solar Expert Posts: 3,821 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
These panels still show almost 40 volts each on a sunny 78F day at 1pm. 

The other panels showed readings that I did not expect. Something like 2.2 from the neg. cable and 1.0 from the positive cable. 

The four suspected panels generally showed nothing at all with the clamp meter. First time I have used a clamp meter. My technique is up for debate. 
First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #2
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    FWIW, I find I have to "zero" mine before every read to get repeatable reads.

    What stage is the bank at?.  Mine would likely be floating at 1pm on a sunny day at this time of year, and absent loads the arrays wouldn't be putting much out.

    Maybe silly question, but the clamp meter definitely does DC (many AC ones don't)?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • softdown
    softdown Solar Expert Posts: 3,821 ✭✭✭✭
    #3
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    Estragon said:
    FWIW, I find I have to "zero" mine before every read to get repeatable reads.

    What stage is the bank at?.  Mine would likely be floating at 1pm on a sunny day at this time of year, and absent loads the arrays wouldn't be putting much out.

    Maybe silly question, but the clamp meter definitely does DC (many AC ones don't)?
    Good question and I did not check. It was a cloudy and I have been running the well pump and charging the forklift battery at "40 amps - 12 volts". Though the meter reads closer to 20 amps unless the battery is really low. 

    I would think the panel read outs up on the roof would be independent of the battery bank stage from a voltage perspective.
     Since I recently ran the well pump and am charging a large battery - the array would likely be feeding a good energy stream to the battery bank. Had not even thought of that - being a clamp meter absolute rookie.

    Yes this clamp meter has a DC setting. The 9 volt battery was down to 8.9 volts and the meter was starting to act "tipsy". Replaced the battery with one reading 9.55 volts. 
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    edited August 2019 #4
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    Personally, I would suspect a wiring issue (combiner box/J-box/line fuse, MC connector, corrosion etc) before I would assume a PV is gone south so to speak.  Isolate each panel and measure current and voltage, on each.

    Tony
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  • softdown
    softdown Solar Expert Posts: 3,821 ✭✭✭✭
    #5
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    icarus said:
    Personally, I would suspect a wiring issue (combiner box/box/line fuse corrosion etc) before I would assume a PV is gon south so to speak.  Isolate each panel and measure current and voltage, on each.

    Tony
    Thought I was doing that with the clamp meter a few inches from the panel electrical boxes. 

    The fuse lead on two of the panels is a really great idea. 
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,440 admin
    #6
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    What brand/model of panels? I have BP-175 (Or something like that--175 Watt BP solar panels). Turned out that about 1/2 of my panels had gone higher resistance/poor connections in the J-Box. It was a manufacturing/design defect. It was easily seen if you did an Isc (short circuit current) measurement on each panel). More or less, the "bad panels" had about 1/2 or less Isc (in good sunlight) vs the "good panels".

    For me, they failed after about 5 years on my GT solar... Because GT Solar pulls 100% of available power (Vamp and Imp) of the panel available panel/sun power--I would guess they would fail sooner than an off grid/battery based system where much of the time less than 100% full current is drawn.

    If you looked very carefully through the top cover glass at the area above the J-Box, there was a very light brownish rusty/coffee colored "stain" from excessive heat in the (sealed) J-Box in the "bad panels".

    BP Solar did standby their panels and replace them all (this is over 10 years ago now). They got out of the solar business around that time (although, I understood that they continued to honor their warranty).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • softdown
    softdown Solar Expert Posts: 3,821 ✭✭✭✭
    #7
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    BB. said:
    What brand/model of panels? I have BP-175 (Or something like that--175 Watt BP solar panels). Turned out that about 1/2 of my panels had gone higher resistance/poor connections in the J-Box. It was a manufacturing/design defect. It was easily seen if you did an Isc (short circuit current) measurement on each panel). More or less, the "bad panels" had about 1/2 or less Isc (in good sunlight) vs the "good panels".

    For me, they failed after about 5 years on my GT solar... Because GT Solar pulls 100% of available power (Vamp and Imp) of the panel available panel/sun power--I would guess they would fail sooner than an off grid/battery based system where much of the time less than 100% full current is drawn.

    If you looked very carefully through the top cover glass at the area above the J-Box, there was a very light brownish rusty/coffee colored "stain" from excessive heat in the (sealed) J-Box in the "bad panels".

    BP Solar did standby their panels and replace them all (this is over 10 years ago now). They got out of the solar business around that time (although, I understood that they continued to honor their warranty).

    -Bill
    Grape Solar I believe - bought through Costco a couple years before I installed them. Now I suspect the panels are good. Bad fuse on two that are wired together. Bad connections or charge controller on the other two.

    I know exactly what you mean about the discoloration above the  J-boxes. I believe those are the exact panels that I bought about 3 dozen of a few years ago. About six were bad. Their voltage readings are highly similar to my Grape Solars - I figure the "architecture" is quite similar. 

    If you had measured the voltage output on the bad panels I suspect the readout may have been zero on a few - that is what I show on the bad panels that clearly show the overheating on the J-boxes. I heard these can be fixed - in theory anyway. 
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #8
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    On two occasions I've had MC4 connectors go high resistance and not pass current, just another possibility not to be overlooked.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,045 ✭✭✭✭✭
    #9
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    The strain relief on the junction boxes of those questionable BP Solar panels was inadequate. Many of the failed panels would show voltage readings that jumped all over the place when the bad lead was wiggled, among other things like the mentioned stain/scorch marks. Some of the bad panels were scorched so bad that the encapsulant was charred.

    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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