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NiCd Battery Experts?



Real NiCd battery experts?

PCsat's batteries presently get 65 minutes of charge and then 35 minutes
of discharge.   Discharge is deep to below 1.0 volt per cell.  Even the
minimum load is not low enough to make it through eclipse  due to the
degraded condition of our  batteries and our 50% reduction in solar power
input due to loss of the -Z  panel in the southern hemisphere.

GIVEN that we are going to go through a deep discharge anyway, the
question is, "which will  hold off the inevitable  cell-reversal/cell-
shorting failure the longest:

1) Putting the most charge in the battery? (wider cycle)
2) Putting less charge in the battery?  (deeper cycle but less range)

GIven that neither of them are sufficient to prevent deep discharge.
Which one will last longer?

The presumed answer is (1).  But "how much better" is (1) than (2) if say
the ratio of charge rate differnce is only say about 20%.  OR, is there
some subtle and not so obvious second order effect that says if you keep
the batteries less charged, that the "cycling" damage is reduced.  In this
case, we could turn on EVERYTHING and make sure the batteries do not get
much charge before the next full discharge..

The option of just turning off everything, keeping batteries dead for 3
weeks and then awakening to great sunshine would be nice, but is not
possible.

Right now we are taking the assumption that the differences between (1)
and (2) are not going to make that much difference over the next 300
cycles, so we may as well let the users use it... (option 2).

Before you reply, remember that all of us HAMS consider ourselves as
experts in NiCd's, just assume we already have more than enough opinions
already and don't need any more...  But documentable and proven facts are
welcome...

de WB4APR@amsat.org, Bob

PCsat WEB  page     http://www.ew.usna.edu/~bruninga/pcsat.html

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