Re: NTLK Re: Batts in the freezer

From: Ed Kummel (tech_ed@yahoo.com)
Date: Sun Jul 09 2000 - 23:16:17 CDT


I remember talking to an engineer at Alexander
Batteries about the so-called memory effect. They
obviously believe that the memory problem does exist
in all rechargeable batteries and sell quite a few
expensive devices to counter act this memory problem.
I used to work for a company that rented cell phones
and before that company that rented walkie-talkies.
Both devices requiring rechargeable batteries. Each
battery would be rented perhaps 3-4 times a month with
who knows what kind of charge/discharge cycle the
customer inflicted to it. Using the battery analyzer
from Alexander Batteries, we would be given an
accurate readout in volts and mAh for each battery
tested. (the device was a $1,500 battery
tester/conditioner) If the values fell below a
predefined level, then we would condition the battery.
This entailed a deep discharge and a full charge. This
is repeated two additional times for a total of 3
discharges and 3 charges. Unless the battery was at
the end of it's life, in every case the mAh would
increase to within 1-5% of it's original value! (we
indicated each battery's value on a lable on the back
of each battery) This technique was used on over
10,000 batteries consisting of NiCAD, NiMH and Lion.
In some instances when we knew that the battery was
good, but a deep cycle would not revive it, we would
use a pulse charger. I'm not too sure how it worked,
but it used some kind of positive/negative pulse
combined with a charge/discharge in quick sucession.
The engineer was sworn to secrecy because of a pending
patent, but he did say that it pulsed between a
charge/discharge over 100 times/sec. He wouldn't go
into details. The company I was with was a beta tester
for the device and it did work. I was even able to get
over 100 additional charges out of a NiCAD that was
leaking (it was a rare and hard to get flatpack NiCAD.
We were working with a developer to create additional
batteries and needed this last one for a short time).
While it only held 3/4 of it's original charge time,
it did work. In all, the company had over $30,000 in
battery equipment and about $1 million in batteries
that needed to be kept in peak condition at all times.
Professional level battery conditioners DO work in
maintaining battery efficiency!
Ed
web/gadget guru
--- NewtonOz <newtonoz@ix.netcom.com> wrote:
> Your eM@il from ratinox@peorth.gweep.net on 7/4/00
> 8:45 PM said this:
>
> >Well, no, because "memory" is a myth. It doesn't
> occour except in sintered
> >plate nickel-cadmium cells of a type used in early
> telecommunications
> >satellites (Telstar and such), and then only under
> exacting laboratory
> >conditions. Modern cadmium paste cells simply do
> not suffer from charge
> >cycle memory. What is frequently called "memory"
> is in fact permanent
> >physical damage to the cell caused by either
> overcharging or
> >overdischarging. Once such damage occours the cell
> is ruined; there is no
> >way to fix the damage. Freezing it will not help,
> and could cause more
> >damage.
> >
> >Under normal use, cadmium crystals will form within
> the paste; this reduces
> >maximum charge capacity of the cell. THIS IS
> NORMAL. It is not memory; it
> >is the normal life cycle of a NiCd cell.
> *OCCASIONAL* deep discharge of
> >NiCd cells will break up these crystaline deposits
> somewhat, restoring some
> >of the capacity of the cell. But it is perfectly
> normal for the maximum
> >charge of a NiCd cell to gradually decline over
> time.
> >--
>
> Hmm... recalling from chem classes from long ago...
>
> I seem to remember that the crystalization can be
> counteracted in NiCads
> by using a trickle or quick charge that is over the
> usual voltage. I
> can't remember which. But I do remember that using
> this method decreases
> the battery's life anyway, which means it should
> only be done for
> batteries for which you have no replacement. "S.S.
> Rat" is right, there
> is no such thing as a "memory" effect for modern
> batteries that are used
> normally. This is just a catch phrase that has
> charmed the masses who
> know no better.
>
> The best thing for you to do is have at least three
> sets of batteries.
> One set should be in use, one set should be for
> standby, and one should
> be charging. It doesn't matter whether you use the
> batteries all the way
> or not; charge them when you find it handy. The
> discharge of a NiCad to
> the minimum voltage ONCE EVERY 30 or so times will
> be sufficient to break
> the crystals. Most people will do this unwittingly
> during the course of
> the battery's life anyway.
>
> -Oz
> of NewtonOz
>
>
>
> With NiCads, and regular NiMH cells, you are going
> to have full discharge
> from 27 to 35 days, depending on the battery age.
>
> -The Folks at NewtonOz Items
> newtonoz@ix.netcom.com
>
> (818) 781 1009
> Business Hours:
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>
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=====
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