1 panels seems hotter

KhellSkKhellSk Registered Users Posts: 82 ✭✭

Hello everyone, im glad to be back here asking questions. I always learns tons form you guys so thanks!

I have 5x 15.6Vmp 3.3amp panels but one is a tad different, Same look same frame, tested the same with a tester. its the back and JB that are different. Anyhow, That one seems to melt snow and ice a lot faster. Right now it windy, around -4F, ice is forming and snow is accumulating on others, not that one.

Any concerns I should have ?

[2x Flooded  6v 210ah][12v 30a 400wMax CC]
[5x 48w 15.9Vmp + 1x 100w 17Vmp]


  • mcgivormcgivor Solar Expert Posts: 3,274 ✭✭✭✭✭

    The 100W module is double the output of the others which would explain why it may be warmer, the VMP of the other 5 is actually quite low 15.6 or 15.9V which may contribute, but if it has been working for some time, there is probably no need for concern. The colour of the surface may a also be a contributing factor.

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    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
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  • KhellSkKhellSk Registered Users Posts: 82 ✭✭

    Its one of the 48w thays hotter.. not the 100w. Plus they r individually isolsted by a blocking diode ao i dont see why that one is warm enough melt a lot more than other

    [2x Flooded  6v 210ah][12v 30a 400wMax CC]
    [5x 48w 15.9Vmp + 1x 100w 17Vmp]

  • jonrjonr Solar Expert Posts: 1,360 ✭✭✭✭

    You tested volts and amps while in place?

    I am available for custom hardware/firmware development

  • BB.BB. Super Moderators, Administrators Posts: 30,049 admin

    It always bugs me when something that, should be otherwise identical, behaves differently than others in a set.

    If you do not have a DC current clamp meter (measure the current in each panel to see if they are working correctly), unplug one panel at a time and check the charge controller to see if the current drops equally with each panel (i.e., drops ~2 amps each time, assuming lots of sun and a battery bank/load that is drawing current).

    For example, if the panel is plugged in backwards, it would be drawing current from the rest. Or, if it has failed internally (shorted cells or connections), it could be drawing current from the other panels and causing it to heat.

    Or, the panel could just be broken (or the wiring back to the charge controller has a bad connection) and not even supplying any current. A solar panel under sun and not supplying current does get hotter than its mates.

    Everything may be fine too... But in solar with "matched panels" and batteries/cells, differences between "matched" sets, usually means something is not right.


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • KhellSkKhellSk Registered Users Posts: 82 ✭✭

    I tested again individually in open and short circuit and everything is pretty close. Cc doesnt read current. Panel isnt backward or the tester would have read negative. They are all isolated by blocking diodes. Its negative wire had 2 strands broken but even after fixing it, its still melting snow faster. Maybe the blocking diode failed and its drawing current.in but with the sun raising above the tree line now i dont have problem charging anymore even if.my c- rate is smaller than it should.

    [2x Flooded  6v 210ah][12v 30a 400wMax CC]
    [5x 48w 15.9Vmp + 1x 100w 17Vmp]

  • mike95490mike95490 Solar Expert Posts: 8,610 ✭✭✭✭✭
    edited February 2019 #7

    Blocking Diodes have no place in modern solar gear, except when enhancing a sellers sales revenue . They cause power loss and add points of failure, and their function has been incorporated into modern charge controllers

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  • PluckaPlucka Registered Users Posts: 107 ✭✭

    Global warming 😎

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