Re: [amsat-bb] ECHO Battery life

["Robert Bruninga" <bruninga@xxxxxxxx>]

>>> 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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