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Difference in NiCad replacement batteries

Discussion in 'Electronic Repair' started by Puddin' Man, Aug 5, 2011.

  1. Puddin' Man

    Puddin' Man Guest

    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."
     
  2. shrtrnd

    shrtrnd

    3,673
    453
    Jan 15, 2010
    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.
     
  3.  
  4. Puddin' Man

    Puddin' Man Guest

    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."
     
  5. 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.
     
  6. Phil Allison

    Phil Allison Guest

    "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
     
  7. Peter Hill

    Peter Hill Guest

    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.
     
  8. Phil Allison

    Phil Allison Guest

    "Peter Hill"

    ** The man is totally insane.

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



    ..... Phil
     
  9. 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.
     
  10. gregz

    gregz Guest

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

    Greg
     
  11. Phil Allison

    Phil Allison Guest

    "gregz"

    ** 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
     
  12. Probably not. The Norelco "charger" is probably little more than a
    resistor
    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.
     
  13. I've read that charge terminating NiMH by temperature rise is
    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.
     
  14. 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.
     
  15. gregz

    gregz Guest

    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
     
  16. Ah, German precision...
     
  17. mike

    mike Guest

    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.

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

    ba-DUM!

    That's no longer possible.

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

    mike Guest

    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?
    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
     
  20. Phil Allison

    Phil Allison Guest

    "William Sommerwerck"


    ** Nah - probably Jewish and too terrified to stop.





    ..... Phil
     
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