Solar controllers

Discussion in 'Hybrid' started by bad dog, Dec 17, 2012.

  1. bad dog
    Joined: Apr 2009
    Posts: 155
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    Location: Broken Bay, Australia

    bad dog bad dog

    G'day - I'm wanting to compare notes with anyone who has a pure solar/electric drive system (not hybrid). Please redirect me if I have missed a thread on this, but I went back several pages and couldn't see anything.

    I am running 500w of Solbianflex panels via GSL BMPPT800 controller, to a Torqueedo Cruise 2 and a pair of Optima 12v 55AH Blue Tops. The boat an 18' cat.

    I find that the GSL controller does an excellent job of charging the batteries, but it will not drive the motor load directly. In fact, the motor load is 'shielded' from its view behind the batteries.

    This means that the full output of the array can not be utilised.

    The boat still works well, it's only a first world problem! ;-)
  2. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    This is pretty well known in the solar car community (I used to build those in engineering school). Only a handful of solar cars have ever run with a direct array-to-drive connection, and they're extremely finicky. Without a battery, the bus voltage jumps all over the place whenever you tweak the throttle, often swinging beyond the MPPT's ability to compensate.

    The usual configuration is a two-rail (+120V / 0V) DC bus to which the array, motor controller, battery controller (a typical solar car carries 25 kg = 5 kWh of Li-poly batteries) and auxiliary power tap are all connected. The array simply pumps as much power as it can create into the bus. The motor controller takes whatever it needs from the bus (and feeds back into it when braking). The battery stabilizes the voltage, absorbs anything the array's producing that the motor can't use, and makes up any shortfall when you hit the throttle and the array can't keep up with the motor.

    When the motor power equals the array power, no appreciable current is flowing in or out of the battery- it's just stabilizing the voltage, and the array's current is going straight to the motor controller. Very efficient.
    1 person likes this.
  3. bad dog
    Joined: Apr 2009
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    Location: Broken Bay, Australia

    bad dog bad dog

    Thanks Matt,
    We are looking at that idea. Interestingly also, Redarc are looking at the possibility prototyping a controller that will do the same thing, in one sealed unit.

  4. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

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