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Re: ECHO Battery life



Right on the mark Bob!  Finally we are getting to the point where we can
reference most valued publications rather than simply casting about hoping
for the best.  SMAD is probably one of the best references and one of a 
dozen that should be consulted when making any spacecraft design decision!
Cliff K7RR  CUBESAT Cal Poly  

McGrane wrote:
> 
> Hi bob- thanks for info, I know you have made a satellite so I value the
> information. Thank you very much, 73, pat n2oeq
> 
> On Tue, 29 Mar 2005, Robert Bruninga wrote:
> 
> > >>> McGrane <tmcgrane@suffolk.lib.ny.us> 3/27/05 10:29:39 AM >>>
> > >The ECHO batteries are rated for ...50,000 cycles or 10years.
> > >How does depth of discharge [DOD]... affect battery life?
> > >This is a serious question, please ,  informed answers only.
> >
> > >From Space Mission Analysis and Design: For NiCd's
> > For 80% DOD you might get 300 cycles
> > For 60% DOD you might get 1000 cycles
> > For 40% DOD you might get 5000 cycles
> > For 20% DOD you might get 25000 cycles
> >
> > Most space applications design for 20% or less DOD.
> >
> > So it really pays to not deep discharge your batteries. !
> > I know this flies in the face of "consumer wisdom" that
> > says to deep discharge every time, but that is only the
> > recommendation of the Battery MFRS that want you to
> > buy a new battery pack every year!
> >
> > How can they get by with saying such a thing?  Simple:
> > They base their claim on your need for MAXIMUM
> > performance on every use.  In that case, you are
> > trading off maximum LIFE for maximum PERFORMANCE
> > and they are right.  Because the deep discharge and
> > full soak recharge balances the cells so that on the
> > next use, they may last a few minutes longer... But at
> > DRASTICALLY reducing the overall life of the cell (and
> > maximizing their ability to sell you more batteries)..
> >
> > Buyer beware... and be informed....
> >
> > In space, you cannot buy another pack...
> > de WB4APR, Bob
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