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Re: super capacitors



I missed the first part of this, and am well behind, so forgive me if this 
has been suggested already...  But, it would seem to me that the best use of 
a Super cap would be for power situations like we have on PCSat-1, where 
there is enough power on average, but not enough for the peak draw.  Add a 
undervoltage transmit inhibit, and the bird would stretch out the packets 
instead of staying discharged.

Greg  KO6TH


----Original Message Follows----
From: Robert McGwier <rwmcgwier@comcast.net>
To: rhyolite@nettally.com
CC: amsat-bb@AMSAT.Org
Subject: Re: [amsat-bb] super capacitors
Date: Thu, 27 Jul 2006 02:04:37 -0400

Joe and others:

It sounds like you guys need to join the Eagle power team!

Lou McFadin is leading the power effort.  He and his team have proposed a 
highly redundant collection of clusters.

I have already done the calculations for the team that show that a 2700F 
supercapacitor (about what you can buy now) has about the same capacity as 
an ordinary D cell.   We are also have the same kind of lithium batteries 
that are on the Mars rovers and are working so beautifully (same 
manufacturer).    Lou's team is designing a very careful charging system for 
the Li-Ion cells.  If treated properly, the rovers show they will live a 
long life.

In the currently planned orbit,   we will short eclipses and the cells will 
not be discharged a lot.   We will also not have really bad seasons.  Our 
solar panel plans are to have adequate power for our transponders at all sun 
angles and enough to run "paying experiments"  between 1/3 and 1/2 of the 
year.

As engineers with new technologies at our disposal,  we are now able to 
mitigate some of the things which have bitten us before.

Bob
N4HY


Joe Leikhim wrote:
>What about constructing a highly redundant power system of clusters of low 
>voltage batteries and solar cells. Each solar cell would be paired with one 
>NICAD cell and this pairing would include its own low voltage boost 
>regulator (charge pump). There could be dozens of these feeding a higher 
>voltage bus. The failure of a battery, solar cell or boost regulator would 
>not load down the high voltage bus. There would only be a degraded source 
>of current. There would be no requirement for potentially unreliable A/B 
>back up switching as all cells would be on line at a time.  K4SAT
>
>


--
AMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats,
NJQRP/AMQRP, QRP ARCI, QCWA, FRC. ARRL SDR Wrk Grp Chairman
"An expert is a man who has made all the mistakes which can be
made in a very narrow field."  Niels Bohr
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