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Alkaline and rechargeable batteries and devices

Discussion in 'Electronic Basics' started by kimiraikkonen, Nov 7, 2007.

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  1. Hi,
    I heard something but i want to make sure that i experienced that:

    If i use non-alkaline rechargeable batteries (i have GP ones, 1.2V
    NiMH) on a mp3 player, after sometime although battery level is shown
    %50 full, the mp3 player is turned off unexpectedly by itself.

    So, isn't healty to use rechargeable batteries on mp3 players or
    digital cameras?

    If i use non-rechargeable standard AAA alkaline batteries (for once
    use), the battery level info is much more reliable and mp3 player's
    operation life is longer.

    I knew that but i want to see a clear explanation why it is.

    Thanks...
     
  2. BobG

    BobG Guest

    =================================
    If the computer is looking for 1.3 volts and it sees 1.2, it thinks
    the voltage is too low and the batteries need charging?
     
  3. Hi,
    I'm talking about mp3 player or digital cameras. Another issue i don't
    know why rechargeable batteries has labeled 1.2volts?
    But that's not the answer of my question stated in first message.
     
  4. The voltage is determined by chemistry. There's a reason carbon zinc
    and alkaline batteries are 1.5v when fresh, and it's not because someone
    decided to make them that way. That's what basic "cell" puts out. If
    you need higher voltage, you cascade them. Take apart a regular 9v
    battery, and you will see that it's made up of multiple cells, each producing
    1.5v and when added together put out the necessary 9v. Same with any
    higher voltage battery. The chemistry determines the voltage, and the
    only way to get a higher voltage is to put more then one cell in
    series.

    Likewise rechargeables have a voltage defined by their chemsitry, which
    good or bad ends up being slightly less than carbone zinc and alkaline
    batteries. The only way you could boost the voltage is by putting
    more "cells" inside the package, which gets problematic since there
    isn't room to put more than one "cell" in an AA or AAA package and still
    keep current capacity the same. And if you boosted the voltage, it
    would be in 1.2v increments, not the needed .3v increment. Take a close
    look at rechargeable 9v batteries, and many or most of them are actually
    rated at 7.2 volts, ie six times 1.2v. Some squeeze in another "cell"
    to get closer to 9v, but they are an exception.

    Devices that use batteries are generally expecting 1.5volts, though in
    this day of rechargeables that may need to be revisited. So any voltage
    reading is based on the voltage starting at 1.5v (or some multiple if
    there are more than one battery in there) and dropping down. The
    rechargeables start out at 1.2v, which gives an illusion of weaker
    batteries to start with.

    Rechargeables do have less of a "life". If the unit needs a minimum
    voltage, the rechargeables will decay to that voltage before the 1.5v
    batteries, since they start out at a lower voltage. Some equipment
    may even watch the voltage and turn itself off if the voltage goes
    below a certain point, again working against rechargeables.

    Some devices need the 1.5v to start out, and rechargeables aren't the
    way to go. Likewise, some devices that have such a slow current draw
    are better off with alkalines, since they keep their voltage longer
    than a rechargeable.

    Michael
     
  5. Rich Grise

    Rich Grise Guest

    Because NiMHs are crap.

    Cheers!
    Rich
     
  6. It is just fine, *if* the product is designed to support them.
    Virtually all digital cameras support NiMH.
    Lots of MP3 players only support Alkaline cells.
    That is because the MP3 players voltage detection circuitry has been
    obviously designed for Alkaline cells only.
    Alkaline and NiMH cells have very different discharge characteristic
    cells. So it's not always practical to have the one circuit to detect
    both. For example, an Alkine cell will have expended all of it's
    energy when it drops to 0.8V or so. A NiMH cell will have discharged
    all it's energy when it drops to 1V. The circuitry in the device must
    be designed to detect this and extract the maxmimum energy from a
    chosen battery technology.
    Products that support both will usually have a software detectable
    threshold level that you can select in a menu somewhere.

    Dave.
     
  7. Phil Allison

    Phil Allison Guest

    "Michael Black"

    ** Not true at all.

    Alkaline cells are only * nominally * 1.5 volts - real examples test
    around 1.6 volts when unused FALLING almost linearly to below 1.0 volts
    when exhausted.

    Any equipment maker who relies on a voltage of 1.5 volts ( or even 1.3
    volts ) from each alkaline cell for his design to work is a criminal ASS !!

    Very few devices are so *badly designed* that they will not work perfectly
    OK with cells supplying 1.2 volts each.



    ** Complete nonsense.

    NiCd and NiMH cells have a very " flat " voltage discharge curve - the
    voltage stays close to the nominal 1.2 volt value until the cell is
    virtually exhausted. Alkaline cell voltage just keeps steadily falling in
    use until they reach exhaustion at about 0.8 volts.

    Rechargeable NiMH cells * long outlast * alkalines in devices like digital
    cameras.


    ** Only junk designed by total idiots would switch off at more than 1.2
    volts per cell.

    Apparently some crappy MP3 players qualify.


    ** Bollocks.

    Such a ridiculous device would only ever use about 10% of the capacity of an
    alkaline cell.


    ** Yeah - in things like wall clocks and rarely used torches.




    ........ Phil
     
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