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    Does a cap pull power, when the cars off?

    Simple question-
    I have a RF 1 farad cap in my system, its installed exactly as the instructions state and so far I have had no problems with it, what Im wondering though is, does a regular cap (no remote on) still pull power after you shut off your car and go to bed, or go away for awhile or whatever, Im asking because im a little nervous about leaving the car shut off for more than a couple days for fear of the cap draining the battery, I have a Pheonix Gold breaker at the battery that I could easily flip off to avoid drainage problems, but I would prefer not to have open the hood and pop the breaker every time I travel.







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    maylar's Avatar
    maylar is offline Electrical Weenie



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    A perfect capacitor draws zero current when it's fully charged. The clock in your head unit draws more.



    dave
    ----------
    1999 Buick Park Ave Ultra
    Head Unit: JVC KWHDR720
    EQ: Audiocontrol EQL
    Front Stage: Hybrid Audio Technologies Imagine 5.25 mids, Morel Maximo tweets
    Sub Stage: Boston G3 10", 0.5 cu ft sealed
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    stones's Avatar
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    HEY- Thanks for the quick response, I really appreciate that, I owe you a beer




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    imral3 is offline Sponge Bob Rules !!!!!



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    if i had known there was a beer at stake...



    good luck and good listening!

    L8r

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    LJM
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    Re: Does a cap pull power, when the cars off?

    Originally posted by stones
    Simple question-
    I have a RF 1 farad cap in my system, its installed exactly as the instructions state and so far I have had no problems with it, what Im wondering though is, does a regular cap (no remote on) still pull power after you shut off your car and go to bed, or go away for awhile or whatever, Im asking because im a little nervous about leaving the car shut off for more than a couple days for fear of the cap draining the battery, I have a Pheonix Gold breaker at the battery that I could easily flip off to avoid drainage problems, but I would prefer not to have open the hood and pop the breaker every time I travel.
    A cap acts as an open circuit to DC current. Therefore, when a cap is hooked up to a battery it does absolutely nothing.




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    blackgeltabs is offline Knowledge is Power



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    Dont most caps slowly drain over time and when you start you car it powers up again? Im pretty sure its like this in circuit board capacitors. Does anyone know?




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    Originally posted by blackgeltabs
    Dont most caps slowly drain over time and when you start you car it powers up again? Im pretty sure its like this in circuit board capacitors. Does anyone know?
    Real capacitors will loose charge over time; the loss of charge is called "leaking". In reference to an earlier question, a capacitor only responds to changes in voltage according to the equation, i = C (dv/dt). Therefore, when a capacitor is connected across a constant DC source, such as a battery, it will act as a open circuit. Hence, it will not drain the battery when the car is shut down, unless it has an internal short circuit. It is only when the DC voltage is varying that the capacitor will supply a current. For example, when an amplifier begins to draw a large current, the battery's voltage will drop and the capacitor will react by supplying the necessary current on demand. In other words, a capacitor is a transient reservoir of charge.

    LJM




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