[Beowulf] power usage, Intel 5160 vs. AMD 2216

Robert G. Brown rgb at phy.duke.edu
Fri Jul 13 18:25:43 PDT 2007

On Fri, 13 Jul 2007, Jim Lux wrote:

>> I have never seen a NiCd last that long.  One is lucky to get a hundred
>> power cycles out of them.
> Something is seriously wrong.
> Typical Lead Acid should take 1000 cycles (where a cycle is full discharge)
> NiCds, properly charged and used, should last for tens of thousands of cycles 
> (e.g. they use them in spacecraft orbiting the earth 14 times a day)
>> NiMH aren't even doing too well in my copious
>> supply of rechargable batteries at home.  And of course a car battery
>> that makes it to seven or eight years is more the exception than the
>> rule.
> That's more driven by exposure to high temperatures and vibration in the 
> under-hood environment.

Yeah, well, empirically the memory effect kills the NiCds way earlier
than that.  And I don't think anything is "wrong" -- I think that's just
the way OTC NiCds work.  Maybe the space program does it better, but
they probably spend a few thousand dollars each on those 10Kcycle
batteries... and their chargers.

> Just as with UPSes, they carefully design the battery charger/life to not be 
> too long (hence too expensive).  It's a sufficiently well understood 
> engineering exercise that they can draw a fairly accurate graph of charge 
> capacity vs time (with the variability of mfr and use factored in).
> you get real long life in a spacecraft application because they carefully 
> hand select and match the cells, and very carefully manage the charge and 
> discharge profiles.

This I believe.


> FWIW, the Mars Rovers use Lithium Ion batteries, with nominally 1000 cycles 
> life. (which they've exceeded by now) 

Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu

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