[Elecraft] battery care

[Rich Lentz]

-----Original Message-----

I don't see where you got the idea that SLA batteries are meant for=20
emergency use.  I saw no such statement.  Sure it listed emergency=20
applications but it also listed an equal amount on non-emergency=20
applications.  My wheelchair uses a pair of small 33 AH SLA's and after=20
three years of constant use, are just now starting to show signs that=20
they will need to be replaced eventually.

------------------- New

I have worked with SLA batteries that have been use in what I call
"emergency" applications.  Some of these are  more than twenty years =
old.
Only a few have been replaced after less than ten years - BUT rarely do =
the
get used. The battery in my home security (SLA) is over 15 years old, =
and it
did its job on a recent two day loss of power. On the other hand, I have
known several people that have owned and later junked SLA battery =
powered
lawn mowers.  These have died after two or three years and the =
replacement
cost of the SLA batteries was as much as the mower. =20

SLA's only have several hundred cycles in them, less if used as a deep =
cycle
when it was not built as a deep cycle.  A wheel chair SLA battery should =
be
a deep cycle battery and thus you will get your 200 - 500 cycles of
charging.  The K2 battery is not a deep cycle battery, so if you charge =
it
up, take it on a trip and run it down, then you will get less than 200
cycles.

NiCad's are deep cycle batteries, the also give ~ 1000 cycles, but how =
long
did the last in your cell phone?  On the other hand, they last 3 - 5 =
years
in the portable phone that you put back in its cradle (almost) every =
night.=20

The newer lithium batteries have even more cycles but cost even more.

I once saw an analysis of the cost of using the different batteries for
portable operation, and believe it or not, the cheapest was to get the
cheapest alkaline batteries, save them until ready for use, and discard
after use.=20

And as far as "Memory" goes, every case that I have seen in the last 25
years has been one of the individual cells being shot while the others =
are
still good.  6 cells charge up to 8.4+ volts and follow their normal
discharge rate.  But 5 cells when charged with a charger designed for 6
cells will still charge them up to ~8.4 volts.  These quickly discharge =
to
the voltage that indicates "Low Battery" though.  Usually the bad cell =
was
created by overcharging and boiling out one of the cells.  Or letting
discharge to the point that an internal short is created.=20

Rich