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  • testing a cap?

    does anyone know of a way i can test a cap i recently got to see if it is working? i tried and couldn't locate anything

  • #2
    charge it, then get like a 12 volt LED, hook it up, and see how long it stays lit. minute or 2 should be good. If that works, charge it again, and hook up a volt meter and make sure it's not putting out a weak voltage. That's the best way I know.
    Tidder

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    • #3
      How big is the cap?

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      • #4
        Originally posted by Tidder
        charge it, then get like a 12 volt LED, hook it up, and see how long it stays lit. minute or 2 should be good. If that works, charge it again, and hook up a volt meter and make sure it's not putting out a weak voltage. That's the best way I know.
        it wouldn't burn out the led? its like .5 farads i think.

        thanks for the info though

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        • #5
          if you got a good cap it should come with a charging card and what i was told is that after its charged if you put the card back on ( dont charge it ) just see if the green led comes back on if it does your good to go.

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          • #6
            Originally posted by Elderm007
            if you got a good cap it should come with a charging card and what i was told is that after its charged if you put the card back on ( dont charge it ) just see if the green led comes back on if it does your good to go.
            ah i got it used.. i wonder if i just stuck a volt meter on it after charging it that might work.. if all else fails i can stick a screwdriver across the poles and see what kind of spark i get

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            • #7
              nice, I would go with the screwdriver, it will only sting for a sec

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              • #8
                Originally posted by Elderm007
                nice, I would go with the screwdriver, it will only sting for a sec
                A screwdriver?!?! You won't get nearly as accurate a test as your tongue.
                Kefka_Killer.owns(you);

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                • #9
                  Use a volt/ohm meter. Put it on ohms, the resistance should increase as the cap charges from the meter. Switch to volts, voltage should drop as the cap discharges through the meter.

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                  • #10
                    Originally posted by mhorton
                    Use a volt/ohm meter. Put it on ohms, the resistance should increase as the cap charges from the meter. Switch to volts, voltage should drop as the cap discharges through the meter.
                    thanks, i'll try that.

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                    • #11
                      No, it won't burn out your LED(?) Caps store energy, not step it up or down. So if your car is a 12v system (13.?) then your cap puts out the same. All else fails, I got a charge/discharge card that came with my Cap that I'll sell ya for uhh... $5? Sound good? It has LED's on it so you know what's happening.
                      Tidder

                      Try RevFE
                      The best resurrected frontend I've ever used, period.


                      I Wish I could ban people

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                      • #12
                        Originally posted by Tidder
                        No, it won't burn out your LED(?) Caps store energy, not step it up or down. So if your car is a 12v system (13.?) then your cap puts out the same. All else fails, I got a charge/discharge card that came with my Cap that I'll sell ya for uhh... $5? Sound good? It has LED's on it so you know what's happening.
                        thanks but i'll try the voltmeter idea and see what i come up with

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                        • #13
                          Use a lamp

                          Originally posted by mhorton
                          Use a volt/ohm meter. Put it on ohms, the resistance should increase as the cap charges from the meter. Switch to volts, voltage should drop as the cap discharges through the meter.
                          It will take a lot of time for a .5F cap to charge/discharge through a meter... I don't think that would do much good for testing that kind of capacitor.

                          You have to charge it with a resistor in series between the battery and the cap (use a 12V/21W lamp and wait 20 seconds) so that the cap doesn't short-circuit the battery while it is charging (with possible damage to the capacitor). Pay attention to the polarity. After it is charged, connect the lamp to it - a 21W lamp should stay on (to 36% of it's brightness) for about 3.5 seconds.

                          If you try it with a 5W bulb you have to wait about a 72 sec. for the cap to charge and in the discharge cycle the lamp should light for about 14.5 sec. until 36% brightness.

                          If the light stays on for much less time than these, the capacitor is not good, probably with current leakage or someting.

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                          • #14
                            I know this is an old post but I am in process of installing my carp PC and audio system. I am not getting power to my amps and I am currious if it is my 1 Farad Capacitor. I charged it initially to around 12 volts (it seemed to take a long time to charge it considering it should only take a few seconds. After that I hooked everything up and no go. the battery or + side of teh cap reads around 12 volts and the output to the fuse dist block / amps read 1-2 volts. Should this side not say 12 volts as well? Even if the car is turned off right? The reason I say this is i need to double check my remote on line for the amps to see if they are being turned on at all.
                            My BMW 2004 330i

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