Capacitor discharge

[Silver Streak]

Just wondering, how long does it take for a 1 farad capacitor to discharge? With a load, say a small 5 watt bulb, and without a load?

[Luc]

If you consider the half-life time period, the exponential decay would be 1 million hours.

[DrtySthV6SE]

just wondering, y are you trying to discharge it with something so small

[Eye8Pussies]

I've thought about this question too vbefore, and the best way that I figured is to use something that can connect to your cigarette lighter, such as your impact gun or something, and using wires hook it up to your cap....

just let your gun spin for a bit, and I'm sure your cap'll be mostly discharged

[Silver Streak]

Man, lemme rephrase my question...let's say I hook up a cap to my audio system. I run the car, it's charged, turn off my engine, and then disconnect the cap. How long will the cap stay charged for? Does it lose it's charge immediately or does it take hours, days? Basically, does it act as a battery?

I was just using the 5 watt bulb as an example...c'mon master Luc, I know you know!!!

[Luc]

I'm trying to recall the circuit class days. There is a time constant for the capacitor to discharge, and that is equivalent to 1/(RC), I believe, where R is the resistor value. You'll have to parallel wire up the R & C, of course. Obviously, you want to use something like a 10-W resistor (of a value) to handle the discharge. A 5-W light should be ok, I think, but unless you know the load impedance, it would be hard to determine how long it would take to discharge. Yes, it does act like a battery, but unlike it, I don't think it can be deep cycled, only drained.

[rayray]

i remember reading about discharging a cap before installing when i bought my cap (used). i used a test light to discharge it. i thought it would only take 3min or so.... ended up being around 7 - 10 min. don't know if the cap was fully charged or not. i did this before installing it.


-rayray