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Just thinking: Charge controloers

Discussion in 'Home Power and Microgeneration' started by Gordon, Nov 2, 2009.

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  1. Gordon

    Gordon Guest

    Just thinking here. That's about all I can do right now.
    About a future homebrew solar power system. And the
    necessary charge controler.

    What is the common wisdom on charge controlers?
    Is the panal just disconnected from the battery
    when full charge is reached?

    Or can the panal be connected to a dump (diversion)

    If a diversion load is used, is the battery
    disconnected at full charge? Or is the
    diversion load connected across the battery/panal
    If the diversion load has the same rating as the
    panal, it should keep the battery from receiving
    additional charge. The only problem I can see is
    if the diversion load should drop out. That would
    cause the battery to over charge.
  2. vaughn

    vaughn Guest

    In a perfect world, the charge controller would be smart enough to allow the
    panels to continue to supply just enough power to supply system loads while
    preserving the full charge in the battery. Sometimes residual uses are
    found for the heat from a dump load (such as water heating) but other than
    that, nobody has yet explained to me the reasons for a dump load in a PV
    system. The panel can hardly overspeed like an unloaded wind turbine. I
    have never heard of a panel being damaged by its own open-circuit voltage,
    but perhaps someone here will educate me.

    My controller seems to put a partial load on my panels when full charge has
    been achieved. I assume that the controller is just shorting out the panels
    intermittently with a PWM arrangement, thus the panel's internal resistance
    is serving as the dump load, but I don't (yet) know why they bother.

  3. Gordon

    Gordon Guest

    I'm mystified by that too.
    But what really gets me is the idea that there is power to be
    harvested and it has no where to go. I suppose that's the
    attraction of grid tie systems; you can dump as much power
    as you have into the grid.

    I suppose that on a stand alone system, I could just switch in
    another battery.
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