Related snippets:
Memory in NiCds is long debated and minimal with proper
treatment. Memory in NimH does exist (the manufacturers say)
but is small and easily removed when a deep cycle is
resumed. Cause is crystal structure effects and % reduction
is small at worst in NimH.
Prius uses NimH and gets about 10 year life by aggressive
battery management.
Modern consumer NimH of large energy density (say over 1600
mAh in an AA size) mostly do not support long term trickle
charge. Lower capacity cells do. NiCd do. Thermal issues may
be the cause.
Limiting the top and bottom end storage (10% each end) of
NimH is said to allow 2000 cycles of use. (See eg OLTPC). As
little as 500 cycles in more normal use (see manufacturers'
data sheets).
LiIon typically give 500 cycles to 70% capacity. (see
manufacturers' data sheets).
LiIon have typically longest life if stored at about 2/3
capacity. As this is about at the transition from constant
current to constant voltage charge it is easy to do.
Typical LiIon have a 4.3V max charge voltage. Reducing this
to 4.2V markedly increases cycle life at the cost of
reducing charged capacity somewhat. Seems like an excellent
tradeoff to me.
Many people claim desulphation and pulse charging restore
dead as dead LA to life. I can't comment usefully but years
ago experience with desulphation was not good.
LA have excellent shelf life. Energy density is low but
charged and discharged half intelligently they work very
well. I see them as an excellent choice where size and
weight are not issues and disposal can be controlled.
If NiCd packs go flaky after 10 cycles I'd suspect either
low quality cells or low quality chargers. Chargers in cheap
power tools are often very poor - often a series resistor
from a power supply. Boiled NiCds have low lives. My
experience of de-whiskering NiCds is that it often works but
a cell thus treated tends to do it again easily. Connection
of a reverse Schottky diode across each NiCd will stop
whiskering!!!
Vaguely related: FWIW, connection of a FORWARD SILICON
diode across silicon solar cells makes them much much more
immune to partial shadowing effects. A solar panel with a
single shadowed cell will have its output current reduced to
about the capability of the shadowed cell,
Russell McMahon
{Quote hidden}> In my experience, this does not apply so much to Lead Acid
> batteries.
> To me, LA are the most forgiving type out there. It is
> easy to damage
> Lithium Ion (and apparently they do not like to be
> continually charged
> or even stored fully charged, either). LA self discharge
> is pretty
> slow. Takes about 6 months to drain to about 50 to 70% of
> start (that
> is, 50 to 70% remaining).
>>>> For those of you who have restored dead NiCads or Lead
>>>> Acid
>>>> batteries, was it worth it ?
>> For me, it essentially turns out that NiCd, NiMH, and LA
>> batteries
>> are not "worth it", period. They can't stay in a charger
>> getting
>> "topped off", they don't store charged, and storing them
>> uncharged
>> seems to quickly lead to a condition where they will no
>> longer take a
>> charge. I'm prepared to believe that there are
>> circumstance where
>> they behave better than that (use every day, charge
>> overnight), but
>> my usage patterns don't seem to match... I don't care
>> whether the
>> problem are "memory", or "over charging" or something
>> else entirely.
>> They just don't work for me in most applications.
>>
>> Since this means that I tend to get something like 5 to
>> 10 uses out
>> of a NiCD pack before they need "attention", if a zapping
>> gets
>> another 5 or 10 charges, that's pretty good...
sbcglobal.net>:
