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Difference in NiCad replacement batteries

P

Puddin' Man

Jan 1, 1970
0
I've got this old Norelco T6000 Beard Trimmer, designed as a throw-away,
that I've been nursing from year to year by soldering in new batteries.
I fear I'm down to my last solder, expect something to break, rendering
the unit unusable (given my modest skills).

Looks like a AA, Amazon has specs at 600mAh and 1.2V.

What is the best and most-long-lived battery I can buy for such a unit? I
assume there are some differences judging from the price range ($4 to $15).

Have been looking for a good replacement for the unit for years, seen
nothing the least bit impressive. "They don't make 'em like they
used to!"

Thx,
P

"Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
 

shrtrnd

Jan 15, 2010
3,876
Joined
Jan 15, 2010
Messages
3,876
www.allelectronics.com
I'd just get a newer manufacturer NiCad.
Most of them nowadays are more than twice the mAh (milli amp hour) capacity
of a 600mAh one. The charge circuit is the same, the battery between-charge times
is just longer, because of higher battery capacity. (They're ALL 1.2V cells)
Good luck keeping the Norelco running.
 
W

William Sommerwerck

Jan 1, 1970
0
Dave Platt said:
$15).

I recently bought a 2-AA-cell pack for this purpose from Mouser...
part number 6396-1K-F2 / CM1T-AA1000. It uses 1000 mAh NiCd cells,
and cost $5.95 plus shipping.
You could easily get more than twice that capacity by using NiMH cells
or a pack thereof, but if the charge-control circuit in the shaver is
designed for NiCd it might not work all that well with NiMH (might
over- or under-charge the battery, shorten its life, etc.).

Probably not. The Norelco "charger" is probably little more than a resistor
in series with the power supply. A NiMH should have no trouble with that.

Why not get some NiMH cells with tabs from Thomas Distributing? The ones I
used in my Polaroid #365 electronic flash work fine, and the #363 rapid
charger -- designed for nicads -- shuts off properly.
 
P

Puddin' Man

Jan 1, 1970
0
Probably not. The Norelco "charger" is probably little more than a resistor
in series with the power supply. A NiMH should have no trouble with that.

Why not get some NiMH cells with tabs from Thomas Distributing? The ones I
used in my Polaroid #365 electronic flash work fine, and the #363 rapid
charger -- designed for nicads -- shuts off properly.

Hmmmmmmm. I peruse
http://www.streetdirectory.com/travel_guide/159640/technology/nimh_vs_nicad_vs_li_ion.html
and it sez longer (than NiMh) life cycles for NiCd.

If true, I'd likely be better off with NiCd. No?

If the life cycle of 1.2v NiCd rechargables is appreciably variable, what is the
best NiCd I can buy? Brand or mnfgr or ? with the longest life cycle??

Thx,
P

"Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
 
W

William Sommerwerck

Jan 1, 1970
0
Nicads are obsolescent, if not actually obsolete. If you can find NiMH cells
that fit, use them.

I've been listening to my Sony Discman at work. It runs on two AA cells. I
use PowerEx (MAHA) 2700mAh NiMH cells. In two weeks, I've gone through 16
disks of Bach organ works, seven of Hermann Baumann playing valveless horn,
and I'm well into an Andras Schiff collection -- and they're still running
strong.
 
P

Phil Allison

Jan 1, 1970
0
"Puddin' Man"


** FFS - get some real information.

and it sez longer (than NiMh) life cycles for NiCd.


** Absolute nonsense.

The number of cycles quoted by makers is a complete fantasy that has almost
nothing to do with any real life application.

Wiki quotes 2000 cycles for NiCd, but gives no source for that mad claim.

IME, treat NiCd or NiMH cells with great care and you can expect a few
hundred cycles - do anything careless ( overcharge or overheat) and you
can ruin them in one day.



..... Phil
 
P

Peter Hill

Jan 1, 1970
0
"Puddin' Man"



** FFS - get some real information.




** Absolute nonsense.

The number of cycles quoted by makers is a complete fantasy that has almost
nothing to do with any real life application.

Wiki quotes 2000 cycles for NiCd, but gives no source for that mad claim.

IME, treat NiCd or NiMH cells with great care and you can expect a few
hundred cycles - do anything careless ( overcharge or overheat) and you
can ruin them in one day.



.... Phil

I'm using 1000mAh NiMH AA cells from Poundworld, sold in packs of 2
(everything £1, kinda like a 5 and dime) GPB). I'm very happy with
them for TV remotes, wireless keyboard / mice, 80's vintage CBM
calculator and even a hair trmmer. 2 AA cells for 1GPB. As almost
everything has $1 = £1 exchange rate should be able to find some for
about 1$ in USA.

At that price the key issue is how easy it is to rebuild the device
you are putting them in.
 
P

Phil Allison

Jan 1, 1970
0
"Peter Hill"
I'm using 1000mAh NiMH AA cells from Poundworld, sold in packs of 2
(everything £1, kinda like a 5 and dime) GPB). I'm very happy with
them for TV remotes, wireless keyboard / mice, 80's vintage CBM
calculator ..


** The man is totally insane.

Wonder if he uses any of his NiMh cells for what they are good at.



..... Phil
 
G

Geoffrey S. Mendelson

Jan 1, 1970
0
Dave said:
As I understand it, the problem with this approach is the question of
shutting off the charge when the battery is full. NiMH cells are less
tolerant of being overcharged than NiCd, and are best used with a
charger that has a somewhat more sensitive full-charge detector (e.g.
zero-delta-V and/or direct temperature sense, rather than negative-
delta-V as was often used with NiCd cells.

It's slightly more complicated, if you replace NiCad cells in a battery
pack with a temperature sensor, you have to replace the sensor too. NiMH
cells have a much lower "cook temperature" than NiCads.

The other night I was having trouble sleeping and read a very nice article
about modifying Motorola NiCad chargers to properly (and not over) charge
NiMH packs. Since it was late at night, I remember the main points and
that I read it, but not where. :)

Geoff.
 
G

gregz

Jan 1, 1970
0
William Sommerwerck said:
Nicads are obsolescent, if not actually obsolete. If you can find NiMH cells
that fit, use them.

I've been listening to my Sony Discman at work. It runs on two AA cells. I
use PowerEx (MAHA) 2700mAh NiMH cells. In two weeks, I've gone through 16
disks of Bach organ works, seven of Hermann Baumann playing valveless horn,
and I'm well into an Andras Schiff collection -- and they're still running
strong.

Depending on current draw, nicads will deliver more current due to lower
impedance. For motors that can be a problem.

Greg
 
P

Phil Allison

Jan 1, 1970
0
"gregz"
Depending on current draw, nicads will deliver more current due to lower
impedance. For motors that can be a problem.


** Simply not true.

AA cells in NiCd or NiMH have closely similar impedances and hence max
current outputs.

The figure is between 10 and 20 milliohms in both cases.


..... Phil
 
W

William Sommerwerck

Jan 1, 1970
0
Probably not. The Norelco "charger" is probably little more than a
resistor
As I understand it, the problem with this approach is the question of
shutting off the charge when the battery is full. NiMH cells are less
tolerant of being overcharged than NiCd, and are best used with a
charger that has a somewhat more sensitive full-charge detector (e.g.
zero-delta-V and/or direct temperature sense, rather than negative-
delta-V as was often used with NiCd cells.

This isn't a problem if you're charging at a fairly low rate. A good-quality
cell -- nicad or NiMH -- will tolerate an indefinite low ("trickle") charge.

If the resistor is chosen to give a 0.1C charge rate when the cell is at
about 1V, the charge rate when the cell has "fully" charged will be rather
lower ("depending").

It's only in the past decade or so that rapid-charging with auto-cutoff has
become commonplace. Prior to that, almost every nicad device was charged
with a simple series resistor. And guess what? It worked.

As I said earlier, I have a Polaroid #365 electronic flash with NiMH cells
that replaced the original nicads. The #363 rapid charger has no trouble
stopping and switching to trickle charge. It was designed almost 45 years
ago.
 
W

William Sommerwerck

Jan 1, 1970
0
I've read that charge terminating NiMH by temperature rise is
not good or proper, that it has to be done by voltage monitoring.
By the time the NiMH cells heat up, the damage has been done.

Based on what I learned at Microsoft Hardware, this is not true. "Hitting"
the NiMH cell "hard", to the point where it significantly heats the cell,
supposedly gives a deeper charge.

I've have NiMHs get quite warm -- even hot -- in chargers. If one such
occurrence ruined the cell, then most of my cells would be useless. None is.
 
W

William Sommerwerck

Jan 1, 1970
0
Depending on current draw, nicads will deliver more current due to lower
impedance. For motors that can be a problem.

Not in a circuit that regulates the current flow to the motor. Which, of
course, CD players have.

The only case I know of where what you say is true, is the use of nicads in
really cheap electronic flashes. These were designed so that the higher
internal resistance of alkaline cells would limit the current flow. With
nicads, they can overheat and be damaged.
 
G

gregz

Jan 1, 1970
0
Phil Allison said:
"Puddin' Man"



** FFS - get some real information.




** Absolute nonsense.

The number of cycles quoted by makers is a complete fantasy that has almost
nothing to do with any real life application.

Wiki quotes 2000 cycles for NiCd, but gives no source for that mad claim.

IME, treat NiCd or NiMH cells with great care and you can expect a few
hundred cycles - do anything careless ( overcharge or overheat) and you
can ruin them in one day.



.... Phil

I had a bunch of NiMH cells laying around for a few years, they just did
not work anymore.

From using them in model cars and Dustbusters, etc, the general idea 10
years ago was the nicads had lower impedance, but in reading further,
today's NiMH cell are better Z wise.

Still got some 50 year old German nicad packs that still work.

Greg
 
M

mike

Jan 1, 1970
0
William said:
This isn't a problem if you're charging at a fairly low rate. A good-quality
cell -- nicad or NiMH -- will tolerate an indefinite low ("trickle") charge.

I'd like to see a reference that supports that.

NiCd batteries are very tolerant of trickle charging.
Early NiMH cells were very INTOLERANT of trickle charging.
Lots has changed over the years. Maybe they're better now,
but I'd like to see some vendor info on that.

If the resistor is chosen to give a 0.1C charge rate when the cell is at
about 1V, the charge rate when the cell has "fully" charged will be rather
lower ("depending").

It's only in the past decade or so that rapid-charging with auto-cutoff has
become commonplace. Prior to that, almost every nicad device was charged
with a simple series resistor. And guess what? It worked.

Here's some empirical evidence.
Power tools have historically had three charge modes.
The cheapest have a trickle charger. People leave 'em on charge all the
time.
The "better" tools have a fast charger with a thermal coutout. The cell
gets HOT and the charge is terminated by the thermal cutout.

The "best" tools have a fast charger that often measures -deltaV for NiCds
or 0delatV for NiMH.

So, here's the experiment.

Go to a garage sale. Almost every garage sale has at least one battery
powered drill.
Have you EVER found a battery powered drill at a garage sale that had a
good battery? I haven't.
As I said earlier, I have a Polaroid #365 electronic flash with NiMH cells
that replaced the original nicads. The #363 rapid charger has no trouble
stopping and switching to trickle charge. It was designed almost 45 years
ago..

The bottom line is that you should always use the EXACT battery chemistry,
type, model number with the charger designed exactly for that battery.

If you're willing to reverse-engineer the charging circuit, you can often
use alternative cells.
Or you can redesign the charger to match the cells.
Or you can just get lucky with any random selection.
I've been lucky 99+% of the time. But I have also been unlucky.
One day I'll find the rest of the battery pack that exploded
when the lawnmower throws it thru a window.
YMMV
 
W

William Sommerwerck

Jan 1, 1970
0
Here's some empirical evidence.
Power tools have historically had three charge modes.
The cheapest have a trickle charger. People leave 'em on charge all the
time.
The "better" tools have a fast charger with a thermal coutout. The cell
gets HOT and the charge is terminated by the thermal cutout.

The "best" tools have a fast charger that often measures -deltaV for NiCds
or 0delatV for NiMH.

So, here's the experiment.

Go to a garage sale. Almost every garage sale has at least one battery
powered drill.
Have you EVER found a battery powered drill at a garage sale that had a
good battery? I haven't.

If it had a good battery, it wouldn't be at the garage sale.

ba-DUM!

The bottom line is that you should always use the EXACT battery chemistry,
type, model number with the charger designed exactly for that battery.

That's no longer possible.

NiMH "behavior" is "close-enough" to nicad that replacement often works
well.
 
M

mike

Jan 1, 1970
0
William said:
If it had a good battery, it wouldn't be at the garage sale.

ba-DUM!

You're letting your desire to be right overshadow your analysis.
How many battery powered drills does the average family need?
When every other garage sale has one, two or even three dead
drills, the statistics are hard to ignore.
The drills are rarely dead. It's almost always the batteries.

Take a design that was intended to be the cheapest initial
purchase cost based on the crappiest batteries available at the time.
Replace the cells with ones having 5x the capacity.
Now, even if the charger design was proper, fast charge termination
is unlikely to be anywhere near correct...as in "never terminates".

Sure, it often works. You feeling lucky?
That's no longer possible.

NiMH "behavior" is "close-enough" to nicad that replacement

often

I'm in complete agreement. The only thing we seem to differ on is the
consequences of when it DOESN'T work and if those consequences
are acceptable.


works
 
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