Re: MMC or Maxwell? Which is better?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net> 


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, February 28, 2004 9:03 AM
Subject: Re: MMC or Maxwell? Which is better?


 > Original poster: Chris Roberts <quezacotl_14000000000000-at-yahoo-dot-com>
 >
 > Thought that my being one of the 2 geek mmc failures that I should add my
 > two cents. =D
 > If you add all of those strings on the mmc, it could get more expensive
 > than the maxwell, but the mmc still has availability and flexibility on
 > it's side. You can go right to the geek group's website and order several
 > hundred caps to make a super capacitor that would equal the maxwell's
 > current rating, along with being able to change the value and voltage
 > rating to whatever you want. The only thing is you give the geek group the
 > extra grief of trying to fill the order of several hundred caps. =D On the
 > other hand, I have found maxwell's to be extremely hard to find, let alone
 > finding the perfect value, rating, etc.

Surplus Maxwells this is true.  Brand new, you just call up GA and order
them.

This is an interesting point.... you have to be careful comparing brand new
components on one hand, and surplus of uncertain provenance on the other.
Even guaranteed new surplus ("true surplus" as in mfr production overruns,
etc.) has the problem of limited availability (fine for a one-off, if it
happens to work, bad if you have to radically alter your design to fit
what's available (or, part of the fun, as it happens) or if you need to
produce more than one).

I haven't priced new Maxwell caps recently, but I'll bet the LEAST expensive
ones suitable for a TC are going to be >$1000 each. I seem to recall that
low rep rate (1 pulse/sec) storing a few kJ were about $1100, 6 kJ -at- 20 kV
(30uF) was $2500.    The price per kilojoule is pretty constant... high rep
rate caps suitable for a TC are going to be a lot more expensive (on a per
joule stored basis)

You can buy a heck of a lot of brand new geekgroup caps, lay out a PC board,
   and pay a "trained professional" to assemble them for that.



 > Although, IMHO, you can't beat beer bottle caps for price and
availability! =D
 >
 > -Chris
 >
 > Tesla list <tesla-at-pupman-dot-com> wrote:
 > Original poster: "Virtualgod"
 >
 >
 >  > With respect to the question at hand: which is better, I must mirror
Dan
 > M,
 >  > Matt D, Terry, and Dr R's comments. There is no question that an
 >  > appropriate commercial pulse cap has higher current ratings than an
MMC,
 >  > but an MMC will cost significantly less in most circumstances and
deliver
 > a
 >  > similar performance to a commercial cap.
 >
 > Of course you could just add more strings (~8Arms/430Apk each) to the MMC
 > till the current is higher than the pulse cap, though I'm not sure if the
 > cost would still be cheaper than a pulse cap.
 >
 >
 >