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Re: [RFI] Big Farad versus Hybrid Caps?

To: RFI List <rfi@contesting.com>
Subject: Re: [RFI] Big Farad versus Hybrid Caps?
From: Michael Keane K1MK <k1mk@alum.mit.edu>
Date: Fri, 19 Jun 2009 08:59:00 -0400
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
On 6/18/2009 8:35 PM, kd4e wrote:
> Ignoring the hype and the prices - can someone address the
> difference in technology between a big Farad cap and a Hybrid?

I'm assuming that a "big Farad cap" is a colloquial name for an electric 
double layer (aka electrochemical) capacitor 

AFAIK, Hybrid® Capacitors are a product line of Evans Capacitor 
(<http://www.evanscap.com>). Hybrid® caps have a lower Equivalent Series 
Resistance (RSR) and somewhat better "high frequency" characteristics 
than electrochemical caps.

A typical electrochemical capacitor behaves as a capacitor only at 
frequencies < 1 Hz

An  electrochemical capacitor will help with battery "sag" that occurs 
over a timescale of seconds.

However, an  electrochemical capacitor will not provide much filtering 
for load variations that are happening at audio frequencies (like voice 
peaks). To filter out audio peaks you'd want to use a big electrolytic.

Mike K1MK

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