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*To*: tesla-at-pupman-dot-com*Subject*: Re: Big Capacitor?*From*: "Jim Lux" <jimlux-at-jpl.nasa.gov> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)*Date*: Mon, 09 Oct 2000 11:09:44 -0600*Delivered-To*: fixup-tesla-at-pupman-dot-com-at-fixme

Those huge caps, though, have very limited high frequency (meaning kHz in this case) response. At some level, the line between electrolytic cap and rechargeable battery gets fuzzy. A run of the mill car battery is 12V -at- 60 Ah =720 Wh (about 1 HP/hr, btw), or just under 260 kJoule.. that's about 13 kJ/kg (figuring 20 kg mass). Compare that to a 70's energy discharge cap of 5 kJ in a 50 kg can... Of course, the energy discharge cap can dump the energy in a few microseconds, it takes 20 hours to get the rated energy out of the car battery... ---------- > From: Tesla list <tesla-at-pupman-dot-com> > To: tesla-at-pupman-dot-com > Subject: Re: Big Capacitor? > Date: Sunday, October 08, 2000 9:31 PM > > Original poster: "Phillip Heslin" <pheslin-at-home-dot-com> > > Hi folks, > > I think the key here is something that hasn't been mentioned yet. The > size of the cap is a function of the total energy storage of the the cap > as measured in Joules and the energy density of the particular type of > cap. The total energy stored in a cap is calculated with the equation > E=(F/2)*(V^2) where E is the total energy in Joules, F is the > capacitance in farads and V is the voltage. ( I hope I remembered that > correctly) Energy densities vary with the type of construction I.E. > electrolytics have a different energy density than a foil cap. I believe > that the highest energy density record is held by the relatively new > Maxwell powercache capacitors. I have seen a rectangular cap about the > size of a 12 oz coke can with a rating of 2500 farads, yes farads! and > rated at 2.5V > > B.T.W if I mis-remembered that formula, someone please correct me. > > > Safe Coiling! > > Phil Heslin > > > --snip-- > > I have a question or two for any one out there. How big would a capacitor > > have to be, (physical dimensions), to have a value of 1 Farad? I know that > > voltage rating would be a determining factor, but just a ballpark figure. > > Has anybody ever seen one? > > Just curious. > > >

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