# Capacitor Charge Time

by OZwurld
Tags: capacitor, charge, time
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 P: 7 Hello all, I was reading this post on calculating the capacitor charge time: http://www.physicsforums.com/showthread.php?t=145203 . 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. Thanks.
 P: 115 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.
 P: 7 is there a typical value that i should use, or does that all depend on how much current i want?
Sci Advisor
Thanks
PF Gold
P: 12,194
Capacitor Charge Time

 Quote by OZwurld is there a typical value that i should use, or does that all depend on how much current i want?
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.
 Sci Advisor Thanks P: 1,923 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.
 Sci Advisor PF Gold P: 3,686 here's a pretty good overview of large capacitors http://www.vishay.com/docs/28356/alu...troduction.pdf

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