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2010 Solar ventilation capacitor?

Discussion in 'Gen 3 Prius Accessories and Modifications' started by Mikethe3d, Jun 11, 2022.

  1. Mikethe3d

    Mikethe3d Junior Member

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    It bugs me that the fan will only run under direct sunlight when the solar ventilation is turned on.

    Does anyone know if it would be possible to splice in a capacitor somewhere downstream from the solar panel output? so that the fan can run more smoothly when a cloud passes over?

    I know Michael Cline mentioned he put a 25v filter cap on the input of his buck converter, but I don't really care too much about recharging my 12v bat

    Thanks!

    Posted via the PriusChat mobile app.
     
    #1 Mikethe3d, Jun 11, 2022
  2. ChapmanF

    ChapmanF Senior Member

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    Have you done the preliminary sort of drawing-board steps yet, like measuring what current the fan draws while the solar controller is running it, and choosing your target for how long you would like it to keep going under cloud cover, then doing the math for what size capacitor that would take?

    I'm curious what use for the solar vent you have in mind. I think Toyota designed it just as something that keeps the hottest air out of the cabin while you're not around, and since you're not around, you don't notice that the fan comes and goes. Me, while I'm in the car, I don't think the solar fan operation blows enough to keep me comfortable anyway.
     
    #2 ChapmanF, Jun 12, 2022
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  3. PriusCamper

    PriusCamper Senior Member

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    Lol, with the cloudy rainy summer in PNW this year people probably think that system is broken in their Prius... I don't know if a capacitor is going to be able to overcome how little power those low quality solar cells can generate. You might need to add a little more solar power or modify it to run on 12v?
     
    #3 PriusCamper, Jun 12, 2022
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  4. Mikethe3d

    Mikethe3d Junior Member

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    Thanks for the replies, i sometimes sit in my car so it's nice if the outside air temperature is fairly cool.

    I don't really have the electronic skills or patience to do any calculations lol. Would be cool if it could last 10-20 seconds even just to bridge the gap during a cloud. Because the fan seems to stop entirely if the power is just slightly below the minimum threshold.

    Theoretically, I suppose all you would need to do is attach the positive lead of the cap to the output line from the solar, and the negative to body ground? I wonder if that would possibly mess up any of the various relays/control boards. Say like a cap rated for 25vdc and XmA.

    Sorry if it's a silly question, I don't know much about electronics, if such a size of capacitor is even feasible.
     
    #4 Mikethe3d, Jun 14, 2022
  5. ChapmanF

    ChapmanF Senior Member

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    Well, this is where you might have a chance to venture beyond your comfort zone and do a little basic math.

    A capacitor's chief property is its capacitance, C, which is a relationship between its voltage, V, and the amount of charge stored in it, Q. If you measure C in farads, V in volts, and Q in coulombs, Q = CV.

    One coulomb is the amount of charge carried in one second by a current of one amp. So if you had a capacitor of one farad (that would be one honkin' capacitor, it's more common to talk about microfarads or smaller), if you draw a steady current of one amp out of it, its voltage will be dropping by one volt every second.

    So for your project, you'd want to know:

    • what maximum voltage it could get charged to when the sun shines
    • what minimum voltage in can drop to and still run the fan
    • how many amps are needed to run the fan, and
    • how many seconds you want to be able to do that before the voltage has dropped to the minimum.

    That'll give you a ballpark value for C, and then do a little window-shopping to see what's available in that ballpark.

    I don't think I've seen any threads here where somebody else has had quite the same project.
     
    #5 ChapmanF, Jun 14, 2022
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