All about voltages of solar panels

Discussion in 'General Electronics Chat' started by Savor_Savvy, Mar 24, 2009.

  1. Savor_Savvy

    Thread Starter New Member

    Mar 24, 2009
    2
    0
    12VDC (thermoelectric cooler) means it accepts 12V direct current only? No more no less?

    I believe a charge controller can help to regulate a stable 12VDC to the cooler?

    In around 1-2hours in the morning, probably 9-11am, the voltages of the solar panels will drop to about 8-9V and the battery will be in discharge state. Around 11-12am till evening, it will revert back to constant 12-13V (for solar panels) and this time the battery will be in charge mode. May i know why this had happened? Is it because of the low voltage in my solar panels, thus it needed help from the battery to help it to power the cooler, thus the discharge state of the battery?

    Why in the first place the solar panels will have these low voltages, even for like 1-2hours?

    Thanks.:)

    (2 photovoltaic single-crystalline panels connected in parallel)
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,764
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    Uh, no, a TEC is like a lot of solid state devices. It has a rating, if you are high or low it can burn up or run at reduced efficiency, but the range isn't that narrow. You could using 13.7 VDC from a car with no problems.

    The main thing about TECs is you have to have a way to dump the heat on one side. A fan on a heat sink is recommended, usually on both sides. This is a 4A 12VDC unit I have kicking around, I plan on using it my computer eventually.

    [​IMG]

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  3. Savor_Savvy

    Thread Starter New Member

    Mar 24, 2009
    2
    0
    Thanks ya. But im interested to find out more about the low voltages that had happened. Anybody know?
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    A shadow on part of the panel will drastically reduce the output. A shadow horizontally across the panel will nearly eliminate the output.

    Shadows create a potential difference within the cell. The shaded part of the cell will have a lower potential than the lit part, and current will flow inside the cell instead of through your load. This will hinder the entire string of cells in series on the panel. A horizontal shadow will hinder all the strings.
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,764
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    Are you using the TEC to keep the batteries cool? One thing I should mention, TECs are noteriously inefficient, a standard cooling unit using a compressor uses less juice. TECs are popular because they are simple, and have no moving parts.

    This will change over time, I've read several articles where improvements in the lab will eventially become commercial.

    If my assumetion is correct, and you are working on batteries, you would get better results with heat sinks and fans to dump the excess heat.
     
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