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Capacitor Charge Time

  1. Jun 22, 2014 #1
    Hello all,

    I was reading this post on calculating the capacitor charge time:
    Code (Text):

    My problem is i have a capacitor (1000uF) and i want to determine its charge time but dont know the R value, is it something i chose arbitrarily or should it be in a datasheet.

  2. jcsd
  3. Jun 22, 2014 #2
    It should come from the circuit. If your resistance is at or near 0, then your current is very large and your capacitor would fill up instantaneously.
  4. Jun 22, 2014 #3
    is there a typical value that i should use, or does that all depend on how much current i want?
  5. Jun 22, 2014 #4


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    In the limit, it absolutely depends upon the resistance (and the Inductance) of the rest of the circuit. In real life, a Capacitor is never charged "instantaneously". The leads and internal structure of the C will also have resistive and inductive components; when using Capacitors at RF, the self Inductance can be very relevant; any Capacitor can resonate and behave as a short circuit, open circuit or even an Inductor, above self-resonance.
  6. Jun 22, 2014 #5


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    The critical parameters relating to minimum charge time will be specified in the manufacturers data sheet.
    1000uF will almost certainly be electrolytic, so the parameters will be;
    1. ESR, the effective series resistance. 2. Ripple current, I_ripple. 3. Temperature rating.

    If you try to charge an electrolytic capacitor too quickly, the high current flow may fuse the internal foil. That can also happen if you short circuit a capacitor. If you repeat the charge-discharge cycle often, the I2R power dissipated in the capacitor ESR may overheat the electrolyte. Keep the current below the ripple current specified.

    To charge a capacitor, C, from a fixed DC voltage, V, through a resistor, R, will require the minimum resistor value to be R = V / I_ripple.
  7. Jun 22, 2014 #6

    jim hardy

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