Alt-BEAM Archive
Message #05144
To: beam@sgiblab.sgi.com
From: Bob Shannon bshannon@tiac.net
Date: Thu, 08 Jul 1999 19:09:46 -0400
Subject: [alt-beam] Re: Supercaps
Steven Bolt wrote:
> On Wed, 7 Jul 1999, Wilf Rigter wrote:
>
> > In the latest Newark Electronics Cat.117, page 83
> > ELNA super caps
> > DZ series - radial lead
> > 100F @ 2.5V $81.10
>
> Boggles the mind. Tad expensive, too - may not compare well with an
> NiMH battery.
Right, I understand that the ESR of these 100F caps is very high.
Conversley, a VL2320 Lithium Pentoxide coin cell battery can deliver
more energy than most supercaps, if you need energy as a slow trickle.
If you need lots of power fast, use a battery.
> > and perhaps more interesting
> > DC series - coin
> > 2.2F@2.4V $3.12 (5/8" diameter by 1/16" thick)
About the size of the VL-2320 battery (which is cheaper) but a fraction of
the
energy density.
> Caps are basically two strips of foil rolled up together. Current
> is taken from the ends, so narrow strips deliver less current than
> wide strips.
> In tall caps with a small diameter, the strips are wide and
> relatively short --> less internal resistance, more current for
> your motors.
> In coin type caps with a large diameter, the strips are very long
> and narrow --> high internal resistance, not good for the usual
> BEAM applications.
>
> Just thought I'd mention it.
Actually the large supercaps use bulk porus (sintered) material so that the
energy
storage happens throughout the bulk material rather than on the surface of
the foil (technically the space between the foil).
No one can roll 100 farads of capacitance up that small using a standard
foil plate capacitor.
These supercaps are very high tech toys.
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