To small amperage on 120w system

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  • artvdb
    Junior Member
    • Jun 2013
    • 6

    #1

    To small amperage on 120w system

    I am concerned if this solar system is working correctly.
    Help me understand what is going on.....
    I have 4 6v golf cart batteries.....approx 440ah capacity......
    and 120w portable solar system (which from an earlier post I was informed is to small)
    BUT
    This morning the batteries measured 12.49v....should be between 80-85% charged.
    When I hook the 120w solar to the batteries, the voltage went to 12.71v, but when I measure the
    amperage on the solar line, it registers less than .1 amp (1/10th amp).....shouldn't I see
    amperage?......The system can produce 6.94a according to their documentation.
    Can you help me understand what is happening?
  • daz
    Solar Fanatic
    • May 2012
    • 331

    #2
    Originally posted by artvdb
    When I hook the 120w solar to the batteries, the voltage went to 12.71v, but when I measure the
    amperage on the solar line, it registers less than .1 amp (1/10th amp).....shouldn't I see
    amperage?......The system can produce 6.94a according to their documentation.
    Can you help me understand what is happening?
    If you are charging at a set voltage (eg 13.8V), then the battery will only take as much current as it needs. So if your battery only needs 0.1A, then that is all it will take, regardless of whether your panel outs out 6A or 20A. The deeper the discharge level, the more current the battery will take.

    Comment

    • Wy_White_Wolf
      Solar Fanatic
      • Oct 2011
      • 1179

      #3
      Voltage should have went higher than 12.7 with full sun. I guess you might have had some shading on the panel when you took the readings or early morning and too high of angle bewteen the panel and sun for it to fully produce..

      WWW

      Comment

      • artvdb
        Junior Member
        • Jun 2013
        • 6

        #4
        Originally posted by Wy_White_Wolf
        Voltage should have went higher than 12.7 with full sun. I guess you might have had some shading on the panel when you took the readings or early morning and too high of angle bewteen the panel and sun for it to fully produce..

        WWW
        So far I haven't seen any voltages above 12.7x......it makes me wonder if this product is working correctly, as it is new. I plan to talk to the support group for this product.
        I was expecting to voltages in the 13+ range and some amperage, but so far that has not happened.

        Comment

        • Sunking
          Solar Fanatic
          • Feb 2010
          • 23301

          #5
          Originally posted by artvdb
          So far I haven't seen any voltages above 12.7x......it makes me wonder if this product is working correctly, as it is new. I plan to talk to the support group for this product.
          I was expecting to voltages in the 13+ range and some amperage, but so far that has not happened.
          First you need to understand what is actually going on. If you are seeing a voltage below 12.6 volts, have bright noon sun you should be seeing a charge current approx = to your panels rated current. At that point voltage is irelevent. You will not see the voltage get up to 14 volts until the batteries are almost fully charged up, and at that point the current will taper off.

          Batteries have fairly low internal resistance, and since your have such a small wattage, even when charging at full current of 6 amps you are not going to see much voltage rise until the batteries get almost fully charged. With such a small wattage panel on a 440 AH 12 volt battery you may never see them get fully charged unless you never use the batteries. For 1 12 volt 440 AH battery using PWM charge controller you need 800 watts of panel to generate 40 amps of charge current that the batteries need, or with MPPT charge controller you would need 500 watts to get the same 40 amps.
          MSEE, PE

          Comment

          • artvdb
            Junior Member
            • Jun 2013
            • 6

            #6
            OK I can buy the voltage doesn't have to get very high, but I expected to see some amperage....The panel is rated at 120w and max of 6.94amps.......yet I only see 1/10 of an amp.
            Even though the system isn't large enough to fully charge the batteries, I expected it would put some amps in, but that is not what I am experiencing.
            Shouldn't the 120w panel provide 3+ amps in bright direct sunlight?

            Comment

            • Wy_White_Wolf
              Solar Fanatic
              • Oct 2011
              • 1179

              #7
              Originally posted by artvdb
              OK I can buy the voltage doesn't have to get very high, but I expected to see some amperage....The panel is rated at 120w and max of 6.94amps.......yet I only see 1/10 of an amp.
              Even though the system isn't large enough to fully charge the batteries, I expected it would put some amps in, but that is not what I am experiencing.
              Shouldn't the 120w panel provide 3+ amps in bright direct sunlight?
              Have you tested the panel by itself?

              WWW

              Comment

              • Sunking
                Solar Fanatic
                • Feb 2010
                • 23301

                #8
                Originally posted by artvdb
                OK I can buy the voltage doesn't have to get very high, but I expected to see some amperage....The panel is rated at 120w and max of 6.94amps.......yet I only see 1/10 of an amp.
                Even though the system isn't large enough to fully charge the batteries, I expected it would put some amps in, but that is not what I am experiencing.
                Shouldn't the 120w panel provide 3+ amps in bright direct sunlight?
                Yes it should deliver 6 amps. Perform a Voc and Isc test on the panel at solar noon on a bright sunny day with panel facing directly into the sun. That will tell you where the problem is. If the panel passes the test your CC is faulty.
                MSEE, PE

                Comment

                • artvdb
                  Junior Member
                  • Jun 2013
                  • 6

                  #9
                  OK, I'll perform the test either tomorrow or on the 4th and post the results.

                  Comment

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