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Whats wrong with this panel setup? Really low ma reading!

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  • Whats wrong with this panel setup? Really low ma reading!

    Hey, im setting this panel (9v 300ma) to charge a 2000mah 4.8v battery.

    In the current lighting im getting 6v off the panel and the battery is reading 5.02v.

    Why is my multimeter saying this 300ma panel is putting out only .2mah? In the best lighting on this overcast day I can get the multimeter to read 4.2ma, and directly under a lamp 8ma.



    Any ideas? At this rate the battery wont ever be charging, right?
    Attached Files

  • #2
    Well to start silly you are inside the house where light is only 1/1000 the strength of outside sun light at noon on a bright sunny day. Solar panels are current sources and the current is directly proportional to the amount of light striking the panel. So a .3 amp panel producing .0002 amps indoor s is pretty good considering the light is about 1/1000 intensity as it is outside (.3 /1000 = .0003). You have a lot of learning to do like simple 5th grade math and science. Besides a 5.2 volts on a 4.8 volt battery is fully charged and you cannot put more water in a full glass or else it spills out.

    In addition for your test, the diode serves no purpose
    MSEE, PE

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    • #3
      Did you buy or build that panel? I just built two just like it for a pair of 6 Volt DIY outdoor lights. They work great and the cells only cost me $3. They work so well I just ordered some more.

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      • #4
        Originally posted by Sunking View Post
        Well to start silly you are inside the house where light is only 1/1000 the strength of outside sun light at noon on a bright sunny day. Solar panels are current sources and the current is directly proportional to the amount of light striking the panel. So a .3 amp panel producing .0002 amps indoor s is pretty good considering the light is about 1/1000 intensity as it is outside (.3 /1000 = .0003). You have a lot of learning to do like simple 5th grade math and science. Besides a 5.2 volts on a 4.8 volt battery is fully charged and you cannot put more water in a full glass or else it spills out.

        In addition for your test, the diode serves no purpose
        Man that was a smug answer. My math skills are fine - I did not know that sunlight was that much more powerful inside - I wasn't expecting 300ma inside - but more like 20ma - enough to maintain the battery and run a class D amplifier which uses 30-50mah for 30 mins a day.

        Also, yes I know the battery is full - I only stated voltage so it was clear that the panel was producing more than the battery and the direction of current was more clear.


        I need to do some testing tomorrow when the sun is out - unfortunately the sun had peaked by the time I played with the panel. I need it to work inside in a sunny window, but only enough to generate whatever the battery discharges on its own and 20-30mah to run the amplifier each day. The 8ma I was getting at 3pm probably means I have enough power for the task.

        To Green: Its my first panel beyond the garden light panels so I bought this one, will probably try and make my own next time as I have gotten pretty good at soldering this past year.


        Also in full sun (at 3pm in Maine in the spring) it performs beyond the specs at 350ma.
        Last edited by Naptown; 04-17-2013, 07:24 PM.

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        • #5
          I wouldn't charge a NiMH battery directly with a solar panel. There are good small hobby chargers that would do better and use the proper mode of charge for that chemistry. Yes, you can trickle charge a NiMH but that solar cell would take a full day to charge if not longer.
          PowerOne 3.6 x 2, 32 SolarWorld 255W mono

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