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Super Capacitor operation with internal resistance (ESR)

Super Capacitor operation with internal resistance (ESR)

(OP)
When looking at charge and discharge rates for capacitors (super caps in this case), can you model the device as a perfect capacitor with an external resistor equal to the ESR value? Also, I notice that some vendors list a maximum operating current for their super capacitors and others do not. I assume trying to pull current out of them too fast can harm the capacitor. When you're not given a maximum on the specification sheet what would you limit the current to?

RE: Super Capacitor operation with internal resistance (ESR)

Yes, a resistor and a cap is a valid model. Just watch that the datasheet probably has some margin o the worst case ESR, so it will probably be lower and may vary with temperature.

Imax = Charged voltage / ESR

Z

RE: Super Capacitor operation with internal resistance (ESR)

I believe it's not so much a damage issue as a charge transport issue such that you can't get the charge back out any faster than what's stated. Hence, some companies not listing it as it isn't a damage issue. (but I'm guessing here)

It's all here (including how to model them):
http://www.tecategroup.com/ultracapacitors-supercapacitors/ultracapacitor-FAQ.php

Keith Cress
kcress - http://www.flaminsystems.com

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