What is the least resistance in this RC circuit?

[laclry311]

TL;DR

least resistance in RC circuit

Hello, I know that the lower the resistance the lower the charge/discharge time in an RC circuit, i.e. 5RC is about the charge/discharge time for the capacitor. But how small is the resitstance allowed to be? I'm guessing that the lower the resistance the more the circuit looks like it has just a capacitor (bad,yes?). Is there a specifice value of what the lowest resistance could be?

 

[berkeman]

To answer the question well, you need to consider the source resistance as well.

Is your question about a switched-on voltage source with an output resistance Rs, in series with an explicit resistor R1 and a capacitor C1 that has and equivalent series resistance of ESR1?