Funeral for a Friend [Death of a NiMH]

On Fri, 17 Oct 2003 16:00:53 GMT, John Steinberg wrote:

Recently, I found a missing set of six in two Motorola radios that sat
unused for about six months. All of the NiMHs were brand new at the
time of insertion into the radios, and all but one of the batteries
charged up well after the extended state of inactivity. Still, this one
NiMH has resisted all attempts at resuscitation and it's become
something of an obsession to get him charged again.

Regrettably, he (an how, pray tell, does one actually determine the sex of a
battery?) has probably gone on to his eternal rest.

NiMH batteries have a high self discharge rate. So you don't want to use them in
anything that can sit around unused for a while (no longer that a couple of
weeks). This typically includes flashlights, GPS units, and radios. If you do
use them in those applications, take them out and recharge them every few weeks.
Otherwise, they will self discharge to the point that irreversible bad things
happen to their electrodes, just as if you had actually run them to the ground
in a current drawing appliance.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

John Steinberg wrote:

Chris L Peterson wrote:

Regrettably, he (an how, pray tell, does one actually determine the sex of a
battery?) has probably gone on to his eternal rest.

Sniff I pretty much figured as much, but I wanted to have secondary
confirmation before letting him go.

If NIMH's are at all like NiCADs, here is a website that may
help bring it back from the dead.
http://www.uoguelph.ca/~antoon/gadgets/rejuv.html

Quote:"It is a well known fact that rechargeable batteries have a
tendency to "play possum", appearing to be dead, while merely
napping instead. It is also a known fact that such batteries can
be awakened from their siesta by giving them the proper "wake-up call".
....Nickel-Cadmium batteries have a tendency to grow internal "whiskers"--fine
weblike shorting paths between the internal battery elements--when not used
for prolonged periods of time. Those whiskers eventually discharge the cell
completely. when attempting to charge such a battery, the internal whiskers
short out the relatively small charging current (which is usually only about
1/10th of the cell's ampere rating), preventing the battery from being recharged.
Awakening a nickel-cadmium cell (assuming that it can be aroused) requires
that a high-current be applied to the battery for a couple seconds to
blast away the whiskers. Once the whiskers are gone, you can charge
the battery in the normal manner."

Tom Clarke

On Fri, 17 Oct 2003 16:00:53 +0000, John Steinberg wrote:

Recently, I found a missing set of six in two Motorola radios that sat
unused for about six months. All of the NiMHs were brand new at the
time of insertion into the radios, and all but one of the batteries
charged up well after the extended state of inactivity. Still, this one
NiMH has resisted all attempts at resuscitation and it's become
something of an obsession to get him charged again.

While I like NiMH batteries for certain things, their relatively low cell
voltage (1.2V) and self-discharge rate cause me to avoid them for certain
things. For flashlights, remote controls and such, I use rechargeable
alkalines. I used to have trouble with them blowing up in the charger
(and one or twice in an appliance), but that hasn't happened for a couple
years now. They are only good for 1 or 2 dozen charges before the battery
life gets annoyingly short, but they are about twice the price of normal
alkalines and they have their place in my house. For emergency lights, I
still use just regular batteries.

Russ

I can vouch for the 'high current for a few seconds' method restoring old NiCd
cells but haven't tried it yet on NiMh yet. I've got a big 40,000uF capacitor
that I charge up to 20v and then zap the battery, it works every time.


"Tom Clarke" wrote in message
...
John Steinberg wrote:

Chris L Peterson wrote:

Regrettably, he (an how, pray tell, does one actually determine the sex of
a
battery?) has probably gone on to his eternal rest.

Sniff I pretty much figured as much, but I wanted to have secondary
confirmation before letting him go.

If NIMH's are at all like NiCADs, here is a website that may
help bring it back from the dead.
http://www.uoguelph.ca/~antoon/gadgets/rejuv.html

Quote:"It is a well known fact that rechargeable batteries have a
tendency to "play possum", appearing to be dead, while merely
napping instead. It is also a known fact that such batteries can
be awakened from their siesta by giving them the proper "wake-up call".
...Nickel-Cadmium batteries have a tendency to grow internal "whiskers"--fine
weblike shorting paths between the internal battery elements--when not used
for prolonged periods of time. Those whiskers eventually discharge the cell
completely. when attempting to charge such a battery, the internal whiskers
short out the relatively small charging current (which is usually only about
1/10th of the cell's ampere rating), preventing the battery from being
recharged.
Awakening a nickel-cadmium cell (assuming that it can be aroused) requires
that a high-current be applied to the battery for a couple seconds to
blast away the whiskers. Once the whiskers are gone, you can charge
the battery in the normal manner."

Tom Clarke

"John Steinberg" wrote in message
...
I am, by my own admission, a NiMH junkie. Since 'discovering' them
some years ago, I have amassed a collection of several dozen AA size,
and several chargers to keep them in peak form. So many astro and
astro-related toys use the NiMHs that I just can't break the habit.

Hi John,

You (unintentionally) had me going there for a minute. I scanned the topic
and thought I saw funeral and Nim in the same line. My mind must have
reorganized it as Min and got my hopes up.

Now my hopes have been dashed.

;-(

Chuck Taylor
Do you observe the moon?
Try the Lunar Observing Group
http://groups.yahoo.com/group/lunar-observing/

On the flip-side of all of this, laptop (Li-Ion) batteries need to be fully
discharged on a regular basis or they crystalize and lose capacity. If your
laptop is supposed to go 3 hours on a charge and only goes 30 minutes....
you don't run it down enough before charging.

However, it is also important to recognize that some of these are smart
batteries and they keep track of the number of charge cycles, and the depth
of the cycle. I can't remember (nor do I care to) the calculations, but
there is a point where it gets upside down if you repeatedly perform charge
cycles when the battery is above some percentage threshold of charge, in
relation to the number of cycles. Unlike the crystalized condition, the
battery indicates it has less life, than it does. The smart technology in
your laptop will then indicate the false low condition. By turning off the
System Power Alert options, I've seen my laptop run for two hours on 0%
charge.

Sometimes it's good to boot to DOS (or the F8 screen), and let it run itself
out.... twice. We used to call that "forming" the battery. I don't know what
to do for a Mac laptop.

Just some helpful tips from a former laptop test engineer.

On Fri, 17 Oct 2003 11:53:19 -0500, "Russ W. Knize"
wrote:

They are only good for 1 or 2 dozen charges before the battery
life gets annoyingly short, but they are about twice the price of normal
alkalines and they have their place in my house.

I've heard this before, but it isn't my own experience. I've been rotating
through the same two sets (of four) NiMH batteries for my Coolpix 990 camera for
more than two years now. Each set must have close to 100 charges on it, and
still delivers the original performance, better than 200 pictures per charge.

I also have a pair of NiMH cells in my DSC, and after maybe 50 charges (and a
couple of extended periods of neglect) are still giving me 8 hours of operation
in sub-zero conditions.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

John Steinberg wrote:

I am, by my own admission, a NiMH junkie. Since 'discovering' them
some years ago, I have amassed a collection of several dozen AA size,
and several chargers to keep them in peak form. So many astro and
astro-related toys use the NiMHs that I just can't break the habit.

Recently, I found a missing set of six in two Motorola radios that sat
unused for about six months. All of the NiMHs were brand new at the
time of insertion into the radios, and all but one of the batteries
charged up well after the extended state of inactivity. Still, this one
NiMH has resisted all attempts at resuscitation and it's become
something of an obsession to get him charged again.

Is it *really* dead or is there some way to revive the poor little guy?
He's a Powerex 1600 mAH 1.2 v. model and if he's really gone I can
take the news unfiltered. But, if there's any chance at saving his
little voltage-free body I'm willing to take pay any price, bear any
burden, and suffer any consequence. (Well, I am willing to just buy a
new one, but let's not let him know that just yet.)

etc.

You've plenty of replies by now. If you want a few dozen more, join the
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to . The subject line of the message can be blank.
In the body of the message type the words "subscribe eflight".

On Fri, 17 Oct 2003 18:59:04 +0000, Chris L Peterson wrote:

On Fri, 17 Oct 2003 11:53:19 -0500, "Russ W. Knize"
wrote:

They are only good for 1 or 2 dozen charges before the battery life gets
annoyingly short, but they are about twice the price of normal alkalines
and they have their place in my house.

I've heard this before, but it isn't my own experience. I've been
rotating through the same two sets (of four) NiMH batteries for my
Coolpix 990 camera for more than two years now. Each set must have close
to 100 charges on it, and still delivers the original performance,
better than 200 pictures per charge.

I was referring to the rechargeable alkalines for the 1 or 2 dozen
charges. I have NiCads that are very old but still perform fine because
they are used frequently (and reconditioned once or twice). None of my
NiMH cells have gone bad, though I have only been using them within the
past year or so. One the other side of the coin, I have a rechargeable
toothbrush that has NiMH cells that can only run the thing for a couple of
minutes now (about 3 years old). Probably low quality cells, but I thought
I'd throw that out there....

Russ

John Steinberg wrote:

...

Sexing a battery isn't all that easy, but one sure fire way of doing so
is installing it in a TV remote. If it only allows you to tune to
Lifetime, you've got yourself a female.

Just look on the shape of the top..

D