Does a cap pull power, when the cars off?

[stones 10+ year member]

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 10+ year member]

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

 

[stones 10+ year member]

HEY- Thanks for the quick response, I really appreciate that, I owe you a beer

 

[imral3 10+ year member]

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

 

[LJM]

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.

 

[blackgeltabs 5,000+ posts]

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?

 

[Unregistered]

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