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AMSAT's Power Developments in the news



Many of you have heard that Lew McFadin (W5DID), working with Steve
Bible (N7HPR) and Steve's colleagues (especially Keith Curtis) at
Microchip (the PIC people) have been working on a next generation power
conditioning system. The basic idea is to have a power charge/discharge
conditioner for each cell of the spacecraft's battery pack. This will
allow the use of several different battery technologies (NiCd, NiMH,
LiIon, etc) and also some of the new "super capacitors". Some of you who
were at Dayton may have seen the breadboard mockup of system that Steve
brought and Lew was showing. Lew was also showing some ~2000 Farad(!) 3
volt capacitors (some of us dubbed them "flux gate capacitors").

The SuperCap developments have been exploding of late. One immediate
service is for regenerative braking in hybrid and electric vehicles,
since the capacitors seem to be able to withstand a (virtually) infinite
number of charge/discharge cycles, and then can "soak up" & discharge
huge currents -- must faster than any chemical batteries can do.
Batteries store watt-hours of energy, while capacitors handle large
numbers of watts of power. One German light-rail system employs a total
of 600 2600Farad capacitors for regenerative braking. Some US electric
buses have capacitor banks with 144 18Farad capacitors that deliver 400
Amps at 360 Volts.

Today I received the 11.15.07 edition of Electronic Design magazine, and
there is an interesting technology review paper entitled "Get the
Lowdown on UltraCapacitors" starting on page 45; the article is
available online at
http://electronicdesign.com/Articles/ArticleID/17465/17465.html.

Starting on page 50 (the 3rd page of the online version) The
AMSAT/MicroChip effort is described along with schematics (figure 6,
also http://electronicdesign.com/files/29/17465/Figure_06.jpg). The
closing paragraph (which doesn't mention the planed use of these
concepts on Suitsat2) says:

> Microchip worked with AMSAT-NA, the not-for-profit private
organization that develops
> amateur-radio satellites. AMSATís next big project, the Eagle
satellite, is slated for
> launch in March 2009. To make Eagle function for decades, it will have
a power system
> based on this work that combines solar panels, lithium-ion batteries,
and ultracaps
> in an integrated power system that will optimize the use of each of
those components.

Pretty good publicity!

73, Tom
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