I have a beard trimmer that runs on a Ni-cad battery that I recharge
about once a month when the battery runs low. Recently, the battery
stopped being able to hold a charge. I charged it for ~12 hours,
tested the voltage, and got zero. OK, fine, so I soldered in a new
ni-cad, and everything works fine now. The trimmer is only a few years
old, so I thought the battery died earlier than I would have expected.


Then I got to thinking about the charger, which is just a simple wall
wart. The battery is one AA ni-cad, 1.2 V 600 mAh. The wall wart
charger is labeled 2.3 V, and I measured 7.5 V DC actual output. The
charger is what came with the trimmer, and molded into the trimmer is
something about "use only charger # such-and-such", which is also the
number on the charger. So I'm sure that the charger is the one that
the manufacturer intented to be used with the trimmer.

Did the higher than expected voltage on the charger lead to the early
demise of the ni-cad battery? Should I find a new wall wart that has a
voltage closer to 1.2 V? If so, what current output should it have?
(I save each and every wall wart from every dead appliance that I have
ever owned, so I have a wide selection to choose from a box in the
attic, although I think most of them are 5V and up.)

Ken

Ken wrote:
I have a beard trimmer that runs on a Ni-cad battery that I recharge
about once a month when the battery runs low. Recently, the battery
stopped being able to hold a charge. I charged it for ~12 hours,
tested the voltage, and got zero. OK, fine, so I soldered in a new
ni-cad, and everything works fine now. The trimmer is only a few
years old, so I thought the battery died earlier than I would have
expected.


Then I got to thinking about the charger, which is just a simple wall
wart. The battery is one AA ni-cad, 1.2 V 600 mAh. The wall wart
charger is labeled 2.3 V, and I measured 7.5 V DC actual output. The
charger is what came with the trimmer, and molded into the trimmer is
something about "use only charger # such-and-such", which is also the
number on the charger. So I'm sure that the charger is the one that
the manufacturer intented to be used with the trimmer.

Did the higher than expected voltage on the charger lead to the early
demise of the ni-cad battery? Should I find a new wall wart that has
a voltage closer to 1.2 V? If so, what current output should it have?
(I save each and every wall wart from every dead appliance that I have
ever owned, so I have a wide selection to choose from a box in the
attic, although I think most of them are 5V and up.)

Ken

You found that voltages change depending on how you measure them.

The battery is rated at the voltage it can deliver (likely under a
specific load).

The charger is rated at the voltage it delivers under a certain load.

The voltage you measured was likely with a modern digital meter that
have a very high resistance, resulting in the high voltage recorded.

If you were to measure the voltage when you first put a battery in need
of a charge on it and then measure it again when the battery is fully
charged you are going to get two more measurements, the last likely near
that 2.3V specified for the charger.

Measure the voltage output of that 5V vampire with that same meter and
no load and you might get something about 10V.

The moral of the story, stick with the one designed for the use you
have.

--
Joseph Meehan

Dia duit

"Ken" wrote in message
oups.com...
I have a beard trimmer that runs on a Ni-cad battery that I recharge
about once a month when the battery runs low. Recently, the battery
stopped being able to hold a charge. I charged it for ~12 hours,
tested the voltage, and got zero. OK, fine, so I soldered in a new
ni-cad, and everything works fine now. The trimmer is only a few years
old, so I thought the battery died earlier than I would have expected.


Then I got to thinking about the charger, which is just a simple wall
wart. The battery is one AA ni-cad, 1.2 V 600 mAh. The wall wart
charger is labeled 2.3 V, and I measured 7.5 V DC actual output. The
charger is what came with the trimmer, and molded into the trimmer is
something about "use only charger # such-and-such", which is also the
number on the charger. So I'm sure that the charger is the one that
the manufacturer intented to be used with the trimmer.

Did the higher than expected voltage on the charger lead to the early
demise of the ni-cad battery? Should I find a new wall wart that has a
voltage closer to 1.2 V? If so, what current output should it have?
(I save each and every wall wart from every dead appliance that I have
ever owned, so I have a wide selection to choose from a box in the
attic, although I think most of them are 5V and up.)

Ken

Stick with the recommended unit. The open circuit measurement doesn't mean
much.

1.325 is the voltage of a fully charged cell.

For a longer cell life don't leave it in the charger all the time.

Under charge load it probably is the right charger and voltage of apx
1.36-1.5v. 1.35 is fully charged for a nicad. 1.2v is considered
discharged. Likely just a cheap battery as alot of junk is made. Sanyo
and Panasonic are tops. Just don`t leave in the charger and overcharge,
and over discharging ruins nicads. When it just slows it is dead. 1.2v
is discharged

I've got a Norelco that's doing a similar thing. I carry it in the truck for
when I forget to shave at home.

It's only got one cell. I'm really tempted to drill a hole in the side of
the shaver, and wire on a single AA battery holder. Put a high capacity
NiMH cell in. Then in two years just pop in another cell. Or use an alkaline
(I've got lots of those) and change battery when it gets weak.

--

Christopher A. Young
Learn more about Jesus
www.lds.org
www.mormons.com


"Ken" wrote in message
oups.com...
I have a beard trimmer that runs on a Ni-cad battery that I recharge
about once a month when the battery runs low. Recently, the battery
stopped being able to hold a charge. I charged it for ~12 hours,
tested the voltage, and got zero. OK, fine, so I soldered in a new
ni-cad, and everything works fine now. The trimmer is only a few years
old, so I thought the battery died earlier than I would have expected.


Then I got to thinking about the charger, which is just a simple wall
wart. The battery is one AA ni-cad, 1.2 V 600 mAh. The wall wart
charger is labeled 2.3 V, and I measured 7.5 V DC actual output. The
charger is what came with the trimmer, and molded into the trimmer is
something about "use only charger # such-and-such", which is also the
number on the charger. So I'm sure that the charger is the one that
the manufacturer intented to be used with the trimmer.

Did the higher than expected voltage on the charger lead to the early
demise of the ni-cad battery? Should I find a new wall wart that has a
voltage closer to 1.2 V? If so, what current output should it have?
(I save each and every wall wart from every dead appliance that I have
ever owned, so I have a wide selection to choose from a box in the
attic, although I think most of them are 5V and up.)

Ken

"Stormin Mormon" wrote in message
...
I've got a Norelco that's doing a similar thing. I carry it in the truck
for
when I forget to shave at home.

It's only got one cell. I'm really tempted to drill a hole in the side of
the shaver, and wire on a single AA battery holder. Put a high capacity
NiMH cell in. Then in two years just pop in another cell. Or use an
alkaline
(I've got lots of those) and change battery when it gets weak.

You might want to use at least a C cell.

I wonder if it would happen if it was hooked to 12 volts. DC motors draw
very little current unless they stall. The faster they run the more back
EMF they create. Still, 12 might be too much for it.


I did something along that line. I had an old rechargeable B&D screwdriver
with two sub C cells. They died and the instructions were how to dispose of
the whole thing. I opened it up and about three feet of heavy wire out. I
found that the charger would charge 4 batteries if left on long enough so I
hooked up 4 D cells. It has power now!!

Get rid of the problematic Ni-cads

Go to Wal-Mart and buy the NiMh rechargeables.
They are the same type of battery that digital cameras
often use. The have no real memory effect and are
cheaper than N-cads. You can usually find the batteries
sold with a charging unit. I have found a four AA battery
charger with four batteries for as low as $10 at Wal-mart.

You can also browse http://www.thomasdistributing.com/

Ken wrote:
I have a beard trimmer that runs on a Ni-cad battery that I recharge
about once a month when the battery runs low. Recently, the battery
stopped being able to hold a charge. I charged it for ~12 hours,
tested the voltage, and got zero. OK, fine, so I soldered in a new
ni-cad, and everything works fine now. The trimmer is only a few years
old, so I thought the battery died earlier than I would have expected.


Then I got to thinking about the charger, which is just a simple wall
wart. The battery is one AA ni-cad, 1.2 V 600 mAh. The wall wart
charger is labeled 2.3 V, and I measured 7.5 V DC actual output. The
charger is what came with the trimmer, and molded into the trimmer is
something about "use only charger # such-and-such", which is also the
number on the charger. So I'm sure that the charger is the one that
the manufacturer intented to be used with the trimmer.

Did the higher than expected voltage on the charger lead to the early
demise of the ni-cad battery? Should I find a new wall wart that has a
voltage closer to 1.2 V? If so, what current output should it have?
(I save each and every wall wart from every dead appliance that I have
ever owned, so I have a wide selection to choose from a box in the
attic, although I think most of them are 5V and up.)

Ken

Lead acid battery chargers are voltage dependent (i.e. 13.5v to charge
a 12v battery). Ni-Cad battery chargers are current dependent (i.e. ~
500ma charging current). So the voltages you measured are somewhat
irrevelant. You can take a 12v battery charger and hook a 12v
lightbulb that draws 300-500ma in series with your Ni-Cad battery and
it will charge just fine.
I've done it for years.

Bob S.

wrote:
Get rid of the problematic Ni-cads

Go to Wal-Mart and buy the NiMh rechargeables.
They are the same type of battery that digital cameras
often use. The have no real memory effect and are
cheaper than N-cads. You can usually find the batteries
sold with a charging unit. I have found a four AA battery
charger with four batteries for as low as $10 at Wal-mart.

You can also browse http://www.thomasdistributing.com/

If I am guessing right, the OP needs a battery that is soldered in the
device. He may not be able to find a NiMh with the proper solder strips
attached. Really no need for NiMh as the Ni-cads do just fine.

--
Joseph Meehan

Dia duit

Rich256 wrote:
1.325 is the voltage of a fully charged cell.

A fully-charged cell that's in good condition, you mean. As they lose
capacity through abuse, the terminal voltage goes up.

--
I miss my .signature.

"Ken" wrote in message
oups.com...
The trimmer is only a few years
old, so I thought the battery died earlier than I would have expected.

From my experience in using ni-cads for the past 30 years or so, you did
good. they do not last forever.



Did the higher than expected voltage on the charger lead to the early
demise of the ni-cad battery?

No it is probably just fine. Some chargers give a high reading under no
load. Others can expain it better than I can.
Stick with what you have.

"Joseph Meehan" wrote in
:

wrote:
Get rid of the problematic Ni-cads

Go to Wal-Mart and buy the NiMh rechargeables.
They are the same type of battery that digital cameras
often use. The have no real memory effect and are
cheaper than N-cads. You can usually find the batteries
sold with a charging unit. I have found a four AA battery
charger with four batteries for as low as $10 at Wal-mart.

You can also browse http://www.thomasdistributing.com/

If I am guessing right, the OP needs a battery that is soldered in
the
device. He may not be able to find a NiMh with the proper solder
strips attached. Really no need for NiMh as the Ni-cads do just fine.


The NiCd battery in his device is probably not a standard AA size,either.
It could be a 2/3A,N,or smaller NiCd.("A" cells are slightly larger in
diameter than a AA cell.)

--
Jim Yanik
jyanik
at
kua.net

clifto wrote in :

Rich256 wrote:
1.325 is the voltage of a fully charged cell.

A fully-charged cell that's in good condition, you mean. As they lose
capacity through abuse, the terminal voltage goes up.


ISTR that it takes 1.55v per cell for charging a NiCd.(loaded V)
You need more voltage than what the cell is rated for.

--
Jim Yanik
jyanik
at
kua.net

"Edwin Pawlowski" wrote in
om:


"Ken" wrote in message
oups.com...
The trimmer is only a few years
old, so I thought the battery died earlier than I would have expected.

From my experience in using ni-cads for the past 30 years or so, you did
good. they do not last forever.



Did the higher than expected voltage on the charger lead to the early
demise of the ni-cad battery?

No it is probably just fine. Some chargers give a high reading under no
load. Others can expain it better than I can.
Stick with what you have.




I have a Dustbuster that the first pack lasted for 10 years,the cells are
designed to be charged 24/7/365,while most NiCds are not.
The Dewalt repair center charged less to replace the pack than for what I
could have bought new cells from Digi-Key(of the same charge type).

--
Jim Yanik
jyanik
at
kua.net

"Joseph Meehan" wrote in message
...
wrote:
Get rid of the problematic Ni-cads

Go to Wal-Mart and buy the NiMh rechargeables.
They are the same type of battery that digital cameras
often use. The have no real memory effect and are
cheaper than N-cads. You can usually find the batteries
sold with a charging unit. I have found a four AA battery
charger with four batteries for as low as $10 at Wal-mart.

You can also browse http://www.thomasdistributing.com/

If I am guessing right, the OP needs a battery that is soldered in the
device. He may not be able to find a NiMh with the proper solder strips
attached. Really no need for NiMh as the Ni-cads do just fine.

--
Joseph Meehan

Dia duit



There are a couple pros to using ni-cd over NiMH if the info I read on the
net was actually correct.

Ni-Cd hold a charge for longer when not in use and I believe will endure
more charge cycles then NiMH. Also, NiMH is rather nasty if it is heated to
above a certain (rather high) temperature.

I usually tape the trigger on when my Ni-Cd tools run low and let it
completely drain the battery before I charge it. They hold a good charge
for quite a while. I've found the tool wears out before the battery does...
but I'm a little rough.

On 2 Jun 2005 00:31:38 GMT, Jim Yanik . wrote:

"Edwin Pawlowski" wrote in
. com:


"Ken" wrote in message
oups.com...
The trimmer is only a few years
old, so I thought the battery died earlier than I would have expected.

From my experience in using ni-cads for the past 30 years or so, you did
good. they do not last forever.



Did the higher than expected voltage on the charger lead to the early
demise of the ni-cad battery?

No it is probably just fine. Some chargers give a high reading under no
load. Others can expain it better than I can.
Stick with what you have.




I have a Dustbuster that the first pack lasted for 10 years,the cells are
designed to be charged 24/7/365,while most NiCds are not.
The Dewalt repair center charged less to replace the pack than for what I
could have bought new cells from Digi-Key(of the same charge type).

It is generally accepted that you can charge sealed NiCads at 1/10th
capacity on a continual basis. ( 500mA battery on a 50mA charger)

DJ

Olaf,

Good advice, but I don't agree with taping the trigger to fully discharge
the cells. That is overkill and all of my electrical engineering buddies
have advised me that 100% discharge to avoid memory effects is not
the way to go. When you notice that your drill is struggling to operate,
then recharge at that time. You'll get much better life from the cells.

Gideon

===============

Olaf wrote in message ...

"Joseph Meehan" wrote in message
...
wrote:
Get rid of the problematic Ni-cads

Go to Wal-Mart and buy the NiMh rechargeables.
They are the same type of battery that digital cameras
often use. The have no real memory effect and are
cheaper than N-cads. You can usually find the batteries
sold with a charging unit. I have found a four AA battery
charger with four batteries for as low as $10 at Wal-mart.

You can also browse http://www.thomasdistributing.com/

If I am guessing right, the OP needs a battery that is soldered in the
device. He may not be able to find a NiMh with the proper solder strips
attached. Really no need for NiMh as the Ni-cads do just fine.

--
Joseph Meehan

Dia duit



There are a couple pros to using ni-cd over NiMH if the info I read on the
net was actually correct.

Ni-Cd hold a charge for longer when not in use and I believe will endure
more charge cycles then NiMH. Also, NiMH is rather nasty if it is heated to
above a certain (rather high) temperature.

I usually tape the trigger on when my Ni-Cd tools run low and let it
completely drain the battery before I charge it. They hold a good charge
for quite a while. I've found the tool wears out before the battery does...
but I'm a little rough.

Andy writes

I disagree. It is generally accepted that the 1/10 rate is the
desired rate to charge a NiCad without overheating. Once the
cell is fully charged, you can THEN overcharge it if you leave
it there..... So 1/10 for about 15 hours is a good rule of thumb
to get to full charge...... If you want to "float" it, drop the
charging
current to 1 or 2 ma to just equal the self-discharge rate.

Andy

DJ wrote:
It is generally accepted that you can charge sealed NiCads at 1/10th
capacity on a continual basis. ( 500mA battery on a 50mA charger)

==========

DJ,

Yep - that is the 16 hour charge rate and it is the basis for many/most
dumb chargers. Unfortunately, many of us are in a hurry and some
manufacturers have put out equally dumb quick chargers which will
begin toasting battery packs once they have reached full charge. Sadly,
the general public doesn't realize why their cordless items need new
battery packs every year or so.

Gideon

Andy writes:

Since the best way to charge a NiCad is with a constant
charging current, it looks like the wall wart has been design
to do that. It probably has a rectifier inside and a series
resistor set to approximately:

7.5 - 1.2
---------------- ohms or around 1200 ohms
.05

in which case it is a very inefficient supply, but will provide a
fairly constant charging current of, in this case, 50 ma.

This is a cheap way to do it, but it is foolproof , works very
well, and doesn't have a failure mode that results in a battery
explosion....

You can verify this by reading the open circuit voltage (which
you said was 7.5 volts, and shorting the output to ground and
reading the short circuit current. That gives you the internal
Thevinen resistance. If it is anywhere in the vicinity of 1K-2K,
you know that is what they are doing...... I doubt that there are
any electronics inside the wall wart other than a rectifier and
a resistor, and probably not even a filter capacitor since it
isn't needed......

If this is the case, Meehan is correct when he says you should
not substitute another wall wart since it will not have the current
limiting resistor.

Andy

Gideon wrote:
Olaf,

Good advice, but I don't agree with taping the trigger to fully discharge
the cells. That is overkill and all of my electrical engineering buddies
have advised me that 100% discharge to avoid memory effects is not
the way to go. When you notice that your drill is struggling to operate,
then recharge at that time. You'll get much better life from the cells.

Gideon

===============

Olaf wrote in message ...

"Joseph Meehan" wrote in message
...

wrote:

Get rid of the problematic Ni-cads

Go to Wal-Mart and buy the NiMh rechargeables.
They are the same type of battery that digital cameras
often use. The have no real memory effect and are
cheaper than N-cads. You can usually find the batteries
sold with a charging unit. I have found a four AA battery
charger with four batteries for as low as $10 at Wal-mart.

You can also browse http://www.thomasdistributing.com/

If I am guessing right, the OP needs a battery that is soldered in the
device. He may not be able to find a NiMh with the proper solder strips
attached. Really no need for NiMh as the Ni-cads do just fine.

--
Joseph Meehan

Dia duit




There are a couple pros to using ni-cd over NiMH if the info I read on the
net was actually correct.

Ni-Cd hold a charge for longer when not in use and I believe will endure
more charge cycles then NiMH. Also, NiMH is rather nasty if it is heated to
above a certain (rather high) temperature.

I usually tape the trigger on when my Ni-Cd tools run low and let it
completely drain the battery before I charge it. They hold a good charge
for quite a while. I've found the tool wears out before the battery does...
but I'm a little rough.




Agreed. You can reverse bias the weaker cells in the pack that way and
bugger them up real good.The "memory effect" with nicads is a much
overated problem. About the only times it really comes into play and
reduces the capacity of the battery is with devices like cordless
phones, when they are used in a mode where they get put back on the
charger after each short phone call and never really get discharged very
much at all.

Jeff

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

Actually, it really is a standard AA size. I expected to see a sub-C
or something when I opened it up. I had some good AA NiCd batteries
laying about, so I soldered one in. It didn't have the solder tabs,
but I was able to get a blob of solder to stick to each end without
cooking the battery with heat.

Ken

Ken,

Without getting into the chemistry of ni-cads, keep in mind these facts:

(New) ni-cads are typically good for about 1000 charge / discharge cycles.
Shelf life depletes the charge about 1% a day.
Occasional deep discharge does help you get your 1000 cycles.
Batteries may be kept on the charger continuously in some cases. Let me
explain.

Assume your "AA" battery has a listed current rating of 1100 milliamp hours
(Mah). This means it should deliver 1100 milliamps for 1 hour or 110
milliamps for 10 hours or 11 milliamps for 100 hours. You get the idea. The
1 hour rate (1100) is known as it's "1R" parameter.

Now, regarding chargers, you can charge a totally dead cell at the 1R rate
(1100 milliamps) and expect a complete charge in just over 1 hour. You can
also charge at the 1/10R rate for about 14 hours and get the same results.
The important factor to remember is that once a cell is completely charged,
a high charge rate will cause it's temperature to rise and that's a "bad
thing". The trick is to know when a cell is "full" so the charger current
can be reduced or stopped. Two ways exist to determine a full charge.
Carefully monitor the cell voltage or carefully monitor the internal
temperature (rectal and oral have no meaning here).

In specialized cells (think Motorola commercial walkie-talkies) where quick
charging is desirable, custom batteries are built with internal temperature
sensors. That's why these batteries have more than two contacts.
Customized (smart) chargers use these sensors to know when to reduce the
high charge rate (1R) to the 1/10R rate.

Finally, a ni-cad cell can be left connected to a 1/10R charger indefinitely
with no ill effects. The off-gassing that occurs is offset by the
re-combining chemistry within the cell so overheating does not occur at the
1/10R rate. How do you know if your wall wart is designed to deliver at the
1/10R rate? Easy. If the owners manual indicates a complete charge may
take 14 - 16 hours, you have one. If it says it can charge a dead battery
in substantially less time, you don't.

Nickel metal hydride (Nimh) and lithium ion cells have different rules.
Another time, perhaps.


"Ken" wrote in message
oups.com...
I have a beard trimmer that runs on a Ni-cad battery that I recharge
about once a month when the battery runs low. Recently, the battery
stopped being able to hold a charge. I charged it for ~12 hours,
tested the voltage, and got zero. OK, fine, so I soldered in a new
ni-cad, and everything works fine now. The trimmer is only a few years
old, so I thought the battery died earlier than I would have expected.


Then I got to thinking about the charger, which is just a simple wall
wart. The battery is one AA ni-cad, 1.2 V 600 mAh. The wall wart
charger is labeled 2.3 V, and I measured 7.5 V DC actual output. The
charger is what came with the trimmer, and molded into the trimmer is
something about "use only charger # such-and-such", which is also the
number on the charger. So I'm sure that the charger is the one that
the manufacturer intented to be used with the trimmer.

Did the higher than expected voltage on the charger lead to the early
demise of the ni-cad battery? Should I find a new wall wart that has a
voltage closer to 1.2 V? If so, what current output should it have?
(I save each and every wall wart from every dead appliance that I have
ever owned, so I have a wide selection to choose from a box in the
attic, although I think most of them are 5V and up.)

Ken

"Craven Morehead" wrote in
:




Finally, a ni-cad cell can be left connected to a 1/10R charger
indefinitely with no ill effects.

I do not believe this to be true.
Digi-Key lists NiCds *specifically designed* to be left on the charger when
not in use. If what you said was true,this would not be necessary.
My own experience also shows it to be false.


--
Jim Yanik
jyanik
at
kua.net

Ken wrote:
Actually, it really is a standard AA size. I expected to see a sub-C
or something when I opened it up. I had some good AA NiCd batteries
laying about, so I soldered one in. It didn't have the solder tabs,
but I was able to get a blob of solder to stick to each end without
cooking the battery with heat.

Ken

Same with mine, but I bought a new NiCd and for 25¢ they spot welded the
tabs.

--
Joseph Meehan

Dia duit

I've read this isn't a good idea. Sometimes one cell goes weak before the
others, and then you get voltage reversal on the weak cell.

--

Christopher A. Young
Learn more about Jesus
www.lds.org
www.mormons.com


"Olaf" wrote in message
...


I usually tape the trigger on when my Ni-Cd tools run low and let it
completely drain the battery before I charge it. They hold a good charge
for quite a while. I've found the tool wears out before the battery does...
but I'm a little rough.

Agree. I don't believe in total discharge. I was involved with recharging
banks of NiCad batteries. We never deeply discharged and had them last for
20 years or more. Of course those were big commercial units. We never let
them get below 50% state of charge.

My theory is that memory only shows up if you repeatedly discharge to the
same level of state of charge. Varying the depth of discharge or even just
one deep one with wipe out any accumulated memory effect.

I think more important is the number of discharges.

For tools and the like I keep them on a curcuit where I turn on a switch
occasionaly for a few minutes. A timer would work too.


"Stormin Mormon" wrote in message
...
I've read this isn't a good idea. Sometimes one cell goes weak before the
others, and then you get voltage reversal on the weak cell.

--

Christopher A. Young
Learn more about Jesus
www.lds.org
www.mormons.com


"Olaf" wrote in message
...


I usually tape the trigger on when my Ni-Cd tools run low and let it
completely drain the battery before I charge it. They hold a good charge
for quite a while. I've found the tool wears out before the battery
does...
but I'm a little rough.

Rich256 wrote:
Agree. I don't believe in total discharge. I was involved with
recharging banks of NiCad batteries. We never deeply discharged and
had them last for 20 years or more. Of course those were big
commercial units. We never let them get below 50% state of charge.

My theory is that memory only shows up if you repeatedly discharge to
the same level of state of charge. Varying the depth of discharge or
even just one deep one with wipe out any accumulated memory effect.

There may be something to that. I will add one additional personal
observation. It appears that the earlier (like 1970) NiCds did suffer from
the memory effect much more than today's do. It may be due to different
chargers, but I suspect they made some improvement to battery formula and
design over the years. Those old NiCd batteries in the flashes for the
Polaroid 100 cameras all seemed to have the problem. I recovered many of
them for irate customers back then. Two or three deep cycles did the trick.
That and instructions to allow them to discharge fully from time to time,
seemed to make happy customers out of un-happy ones.



I think more important is the number of discharges.

For tools and the like I keep them on a curcuit where I turn on a
switch occasionaly for a few minutes. A timer would work too.


"Stormin Mormon" wrote in message
...
I've read this isn't a good idea. Sometimes one cell goes weak
before the others, and then you get voltage reversal on the weak
cell.

--

Christopher A. Young
Learn more about Jesus
www.lds.org
www.mormons.com


"Olaf" wrote in message
...


I usually tape the trigger on when my Ni-Cd tools run low and let it
completely drain the battery before I charge it. They hold a good
charge for quite a while. I've found the tool wears out before the
battery does... but I'm a little rough.

--
Joseph Meehan

Dia duit

Jim Yanik wrote:
clifto wrote in :
Rich256 wrote:
1.325 is the voltage of a fully charged cell.

A fully-charged cell that's in good condition, you mean. As they lose
capacity through abuse, the terminal voltage goes up.

ISTR that it takes 1.55v per cell for charging a NiCd.(loaded V)
You need more voltage than what the cell is rated for.

With the charger attached to the battery, 1.55V isn't a bad estimate for
the voltage you'll see at full charge. With the charger detached, 1.325V
is a decent estimate for the battery voltage.

--
I miss my .signature.

Thanks for all the info. I don't recall the exact number, but I do
recall the manual saying something about the charge taking the better
portion of a day. Basically, I try to trim my beard some morning, find
that it is dead, plug in the charger, and then unplug it either that
night or else the next morning if I forget.

Ken

"Jim Yanik" . wrote in message
.. .
"Craven Morehead" wrote in
:




Finally, a ni-cad cell can be left connected to a 1/10R charger
indefinitely with no ill effects.

I do not believe this to be true.
Digi-Key lists NiCds *specifically designed* to be left on the charger
when
not in use. If what you said was true,this would not be necessary.
My own experience also shows it to be false.

Jim Yanik
jyanik
at
kua.net

Digi-Key does not make the batteries; they only sell them. This claim of
unique capability is only sales talk. They claim a special benefit which
is, in fact, common to all ordinary NiCads -- a widespread practice with
sales people.

SJF

"Gideon" wrote in message
...
Olaf,

Good advice, but I don't agree with taping the trigger to fully discharge
the cells. That is overkill and all of my electrical engineering buddies
have advised me that 100% discharge to avoid memory effects is not
the way to go. When you notice that your drill is struggling to operate,
then recharge at that time. You'll get much better life from the cells.

Gideon


Cool! Thanks. :-)

Ken wrote in message
ps.com...
Actually, it really is a standard AA size. I expected to see a sub-C
or something when I opened it up. I had some good AA NiCd batteries
laying about, so I soldered one in. It didn't have the solder tabs,
but I was able to get a blob of solder to stick to each end without
cooking the battery with heat.

Ken
Being a cheap basthud I'd check the battery by subjecting it to a quick
shot at a higher voltage then check to see if the cell is still dead. I've
zapped apperently dead cells back to stretch the life a bit. I hit a cell
with the 12v battery charger (i said quick- a touch ) then I checked to see
if the battery is still dead. Leave it sit for perhaps 6 hrs and see if it
is still holding a charge. About 1/3 of the time , I can manage to get the
dead cell to hold the charge for a while, then I go to a complete slow
charge (a typical 500-740 aa cell) will be charged at 50mah overnight.If you
already have the cel why not give it a shot. I just retired a 500mah aa
nicad that had a 1974 manufacter date. Course it was down to mebbe 40% of
capacity for the last year, but I did get some work outa the battery. Pat

"SJF" wrote in news:d0Ine.56$xr.35@fed1read05:


"Jim Yanik" . wrote in message
.. .
"Craven Morehead" wrote in
:




Finally, a ni-cad cell can be left connected to a 1/10R charger
indefinitely with no ill effects.

I do not believe this to be true.
Digi-Key lists NiCds *specifically designed* to be left on the charger
when
not in use. If what you said was true,this would not be necessary.
My own experience also shows it to be false.

Jim Yanik
jyanik
at
kua.net

Digi-Key does not make the batteries; they only sell them. This claim of
unique capability is only sales talk. They claim a special benefit which
is, in fact, common to all ordinary NiCads -- a widespread practice with
sales people.

SJF





Bulls..t.
It's not "sales talk",it's in their printed catalog.


--
Jim Yanik
jyanik
at
kua.net