4412Views5Replies

# How do you know if a capacitor is finished charging to its full potential capacidence? Answered

How do you know if a capacitor is finished charging to its full potential? Also if you were to have a group of capacitors linked together in a series or parallel fashion how could you determine whether or not the capacitors were charged completely? I am mainly referring to polarized capacitors.

Tags:

The forums are retiring in 2021 and are now closed for new topics and comments.

A capacitor is charged when the voltage across the capacitor equals charging voltage and the current drops to almost nothing.
This simple method works with series and parallel capacitors.
Even after the capacitor is charged you will get a small current, even good capacitors will leak a little current.

technically you can never acutally completly fill a capacitor, you can just get to the point where it doesn;t matter anymore

The equation that describes the charging of a cap is:
Q=Qmax[1-e(-t/RC)], where Q is the charge in the cap, RC is the the time constant, and t is the time since you started charging.

So if I were to have a 470uf cap and I were to charge it for a ten seconds the equations would look something like this? Sorry I don't know how to type in exponents so I just used the carrot symbol.
.00047(1-e^(-10/60))

The capacitor is fully charged when the voltage across it equals the charging voltage, before the charging resistor, or, alternatively, if the voltage across the charging resistor is zero

Series connected capacitors rarely charge to identical voltages, because the capacitor values vary quite widely. When its essential, then high value resistors are connected across each cap.