RE: [amsat-bb] batteries

["Dr Tom Clark" <w3iwi@xxxxxxxx>]

Wayne replied:

> I think the original question was more about battery
> "performance" than battery reliability.  Surely it would be
> desirable to use utilize the dramatically higher energy
> density of new battery technologies IF it could meet all
> reliability requirements.  If Lithium Polymer cells could be
> demonstrated to work reliably in the charge/discharge
> environment of a satellite, why wouldn't we want double the
> capacity with half the weight and volume?
>
> Lithium cells require charging regimes that might not be well
> suited to solar charging in space.  Perhaps there is a long
> list of considerations that make Lithium cells unsuitable for
> use in space.  But the original question was reasonable: Can
> new cell technology such as Lithium Polymer be used in future
> satellites?

Wayne:

Most of the prevailing wisdom, as I understand it, is that if you use a
metric something like [ (watt hours) per (kilogram) per (factors involving
operating temperature range) per (lifetime in charge/discharge cycles) per
(dollar) per (other factors too mentionable to be numerous, including
familiarity and simplicity of implementation) ], then NiCd cells of the type
Larry described are tough to beat.

Larry made a great contribution in establishing the technology and
methodology of making good battery packs. Before his pioneering efforts
20-25 years ago, space qualified battery cells were made of a rare substance
called Unobtanium. The "space rated" cells for AO-7 were flight spares for a
NASA satellite called RAE-B. If we had purchased them, the individual cells
would have cost thousands of $$$ each, and the battery pack has (if I
recall) 12 cells. What Larry did was to develop ways to select the really
good commercial, industrial grade cells from a larger batch for a cost to
AMSAT in the hundreds of $$$ per cell with intelligent screening. Larry's
"problem solved" comment shows his pride that his battery packs have lasted
at least 4 times as long as the expensive "space qualified" did. Give him a
big hand!

However, new technology is happening every day and the old folks (me
included) who were involved years ago need to be replaced. AMSAT certainly
could use a resident "poobah on the mountaintop" "Battery guru" to help make
sensible decisions in the future. Would you be willing to become the expert?

People have asked how to get "hired" by AMSAT. The answer is to identify a
problem and take the responsibility for solving it.

73 de Tom, W3IWI


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