Re: [amsat-bb] ECHO Battery life

[McGrane <tmcgrane@xxxxxxxxxxxxxxxxx>]

Hi kevin- thanks for explanation; very educational, 73, pat


On Sun, 27 Mar 2005, wa6fwf wrote:

> On Sunday 27 March 2005 07:29, you wrote:
> > Happy easter to all from patrick N2OEQ
> > 
> > Regarding ECHO; The batteries are rated for a life of 50,000 cycles or 10
> > years. 
> > 
> > How does depth of discharge and subsequent charge levels affect battery
> > life? This is a serious question, please , serious informed answers only.
> > 
> > Thank you, 73, patrick
> > ----
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> > 
> 
> Hi Patrick,
>    I think that is a optimistic number, the matching of cells surely helps, but 
> Ni-Cads  do best when the are charged, completely discharged and then charged 
> fully, chronic undercharging or overcharging leads to crystal formation which gives 
> you the shorted cells. The worse thing you can have is running a pack down and have 
> one cell empty first and then go reverse voltage, the careful matching of the cells
> helps prevent that. 
>   If you get a really good matched set, where they all discharge and charge equally then you 
> end up with a pack like what was on UO-14, no one cell gets under or over charged and the
> pack lasts for years and years.
>    
>   AO-40's batteries died an early death, IMO they were micro-cycled, AO-40 was supposed
> to be 3 axis with the panels opened and directed at the sun giving you a steady charge current,
> instead because of problems it had to keep spinning with the panels closed, this caused
> a pulsating charge effect on the batteries.
> 
> Hindsight is always 20-20 but plotting the battery voltage you could see the batteries getting worse
> and worse, it probably needed to have charging shut off  let the batteries run down and then recharged
> fully to cycle them and possibly regain some capacity.
> 
> But one could understand when you have a sat of "iffy" reliability from an accident that you tend
> to leave it alone to not make things worse...
> 
>    As far as Echo is concerned I have no doubt Mike KE4AZN is very conscientious and is keeping a close eye
> on the battery health which is the best possible thing that could happen to ensure a long life for
> Echo.
> 
> 73
> Kevin
> WA6FWF
> #19623
> ----
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