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Amperage of capacitor

  1. May 7, 2012 #1
    Dear Experts

    I bought some 3 Farad electrolytic capacitors at 2.5v each.

    I am wondering how much amperage can i get from 1 such capacitors if charged fully and then discharged fully?

    I think this is measured in Amp-hours.

    Is there a formula to derive the amperage from the capacitor's farad rating?

    Please recommend where I can get free samples of super capacitors or boost capacitors.

    Thanks a lot :)


    Best regards
    Ramone
     
  2. jcsd
  3. May 7, 2012 #2

    Averagesupernova

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    You can find what you want to know from some of the most basic electrical laws and formulas. You know, the basics like Q=CV, definitions, etc. When you fully discharge a capacitor from fully charged the current (amps) will be constantly changing. Not sure what you are trying to do here but that is something to think about. BTW, what you call amperage is generally called current and is measured in amperes. Amp-hours is usually something that is associated with batteries. A battery is able to produce a given current for a specified time and the product of those two is amp-hours. A battery that is rated for 100 amp hours can do 10 amps for 10 hours or 5 amps for 20 hours.
     
  4. May 7, 2012 #3

    psparky

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    What will your capacitor be charging? Any time you change the load (resistance)....you just changed the RC constant.

    I'm assume you are using a battery to charge it? Also assuming you are talking about a cap in series with a resistor (load)

    If so.....just google "RC constant formulas"..."or RC transient"....and plug and chug for the current.

    The formula for use of battery looks like this:
    i(t)={[V-Vc(0)]/R}*e^((-t/(RC))

    V is your voltage source......and Vc(0) is your initial charge on your capacitor.

    If you are charging cap....Vc(0) will just be zero........

    If you are discharging the cap.......disconnect the battery....and ignore the V in your formula. I'm assuming Vc(0) will be 2.5 volts in this case.
     
  5. May 12, 2012 #4
    Hello Averagesupernova and Psparky

    Thanks very much for your replies and advice .

    Psparky guessed correctly. I am trying to charge a lithium ion battery.

    Will cyclic discharging of the capacitors to the battery cause the battery to age faster or is constant DC voltage slow charging better for the battery life?

    Thanks!

    regards
    Ramone
     
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