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  • low solar panel output

    ok here goes. I have a very strange problem .I purchased 4 100 watt solar panels about a month apart.I didn't really get serious with them unti about 2 weeks ago
    I connected them in series and got about 83 VOC and about 5 ISC which is about right from what I read.Oh I am using a 30A MPPT CC. I have not been able to get more than 200 watts out this configuration. So as a test I connected the 2 newer panels in series and got about 150 watts with just those two. I have been going round and round with the manufacturer for two weeks.
    They said do this test do that test. I even sent them pictures of the reading at their request.
    Now I decided to buy 2 more 100 watt panels and put them in series with the 2 newer ones.With this configuration I was able to get 350-360 watts.
    It's only logical to me that the 2 older panels are creating my problem,even tho the VOC and ISC are in specs.
    I even tested the 2 older panels separately and only got about 30 watts each on a bright solar day.The others about 80 watts each.Has anybody else seen this problem with panels they had?

  • #2
    Isc looks good because of the bypass diode(s). Voc looks good because the connection is there, but high impedance (cracked trace, bad solder joint, etc). Load test reveals the failure.
    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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    • #3
      thanks I just can't get them to admit that the panels are faulty since the others perform well under the same conditions.

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      • #4
        Originally posted by satman49 View Post
        thanks I just can't get them to admit that the panels are faulty since the others perform well under the same conditions.
        The only thing that might persuade them would be to do an actual load test in which you take one panel and connect it to your MPPT CC into a battery that needs charging.
        Measure both the current and the voltage. If the panel is good, the voltage should be very close to Vmp for your temperature conditions while the current is somewhere not too much lower than Imp.
        If one cell or section of the panel is bad you will see current close to Imp but the voltage while connected (not Voc) will be 1/3 or 2/3 of Vmp instead of Vmp. That will be because only part of the panel will be producing power while the rest (1 or 2 sections) will be bypassed by the (you guessed it)) bypass diodes.

        If you have access to the inside of the terminal box for the panel you could also measure the voltage across each diode while the panel is under load.
        SunnyBoy 3000 US, 18 BP Solar 175B panels.

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        • #5
          We have had rainy conditions the last few days, I'll try that tomorrow. thnx

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          • #6
            I wrote this to them k here are some pics I took today.It was a test of two single panels, PIcs 1 and 2 are with the panel i got back in Janurary and pics 3 and 4 are with the one got in March. both test consisted of 50 ft of "REAL" PV 10awg cable and your 30A MPPT CC battery voltage at about 12.2.V Conditions sunny sky temp 75F and about 950 W/m squared. The load was my minifrig plugged into a 1200 watt power inverter( see pics 5and 6). I really don't know what the issue is with the first two panels I got from you. With the two more 100 watt panels that I got recently and connected in series with what I will call Good panels , do just fine 300-360 watts depending on time of day, it's just the first two panels that are a problem.With that said,I am at a loss as to what it could be. They just don't get it. They said it maybe bad wiring . I was so frustrated with them for not admitting one of their products is defective. (IMHO). If need I will buy anymore panels elsewhere.
            I did measure the voltage across each bypass diode about 7V each The Imp was 1.8A pic1.JPGpic2.JPGpic3.JPGpic6.JPGpic4.JPGpic5.JPG

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            • #7
              Somewhat off topic but possibly a problem.
              Where is the power for your inverter coming from? I see small wire connected to the load terminals of the CC. This is NOT where you want your inverter connected and frankly a mess of wire in general..
              2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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              • #8
                The inverter is connected directly to the battery bank using 4awg wire at the rear of the inverter.The wires that you see on the load are just for a cpl of led spot lights.I know it isn't pretty but functional for now.

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