electrolytic capacitor

[pete g]

how does leakage(parallel) in an electrolytic cap affect capacitance?

[wasedadoc]

It does not affect the true capacitance. It may affect (reduce) the capacitance value indicated by some capacitance meters. It may also reduce the effective capacitance in some circuits such as timing circuits.

[srb1954]

It does not affect the true capacitance. It may affect (reduce) the capacitance value indicated by some capacitance meters. It may also reduce the effective capacitance in some circuits such as timing circuits.

Or it could increase the effective capacitance. It depends on the configuration of the timing circuit.

If you have a capacitor charging up to a threshold voltage e.g. in a 555 timer circuit, the effect of leakage will be to slow the charging rate and it takes longer to reach the threshold voltage. The effective capacitance thus appears to be larger in this case.

[pete g]

so, if i were to measure a cap with an esr meter, a leaking cap would show no evidence of leakage, the esr and cap value would not significantly change. is that correct?

[Zero999]

Leakage will not affect the ESR. It will probably result in a higher than expected reading when the value is tested, on most multimeters. This is because the impedance is measured at a specific frequency and leakage will reduce the impedance.

[RoGeorge]

By "leakage(parallel)" do you mean the parallel leakage resistor, or do you mean the electrolyte leaking out on the PCB and surroundings?

- If it's the first, ESR/capacitance won't tell you the parallel resistance of a capacitor, you need to test for dielectric losses.  A list with a few type of losses, there are more than parallel equivalent resistance:  https://passive-components.eu/esr-losses-in-capacitors-explained/

- If the second, if a capacitor is leaking electrolyte, most probably will show:  lower capacitance, higher ESR than nominal, visual indication and/or bad smell.

[barshatriplee]

This article discusses Electrolytic Capacitors characteristic of leakage current and how it is important to allow 'self-healing':
https://eepower.com/technical-articles/electrolytic-capacitor-leakage-current/#

[pete g]

thanks guys, your comments were very helpful.