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Difference between Lithium Ion and Nickel Metal Hydride

  1. Jul 17, 2015 #1
    Obviously there are MANY differences, but I'm curious about one in particular.

    In an article I read, the creator used NiMH batteries because of their high charge density, but also because they do not require a charge controller and voltage regulator in the circuitry. Why is this, and is there any way a Lithium Ion battery can also function without a charge controller/voltage regulator?
     
  2. jcsd
  3. Jul 17, 2015 #2
    Many modern batteries can be damaged if used incorrectly. Some (not commercial ones I hope) might even burn/explode.

    The lithium ion battery has a problem of lithium metal build up at high current discharge. Lithium is a very reactive metal and can burn easily.

    Disabling safety devices is dangerous/stupid/a no-no. That would include using a battery inappropriately.
     
  4. Jul 17, 2015 #3

    davenn

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    is it a reliable source ?? for me that statement if false
    all NiCds and Ni Metal Hydrides I have ever owned have timed charge controllers
     
  5. Jul 18, 2015 #4
    It's from a peer reviewed journal entry, but it's ~10 years old.
     
  6. Jul 18, 2015 #5

    meBigGuy

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    A timed charge controller for a NiMH or NiCad battery is a totally different animal from a 3 phase charge system for Li-ion.

    A li-ion charger starts with a small charge current until the battery reaches a low voltage threshold, then applies a constant current (usually 0.1C) until it reaches precisely 4.2V (+- 50mV), then maintains exactly 4.2V by progressively reducing the charge current until the current is below a "fully charged" threshold. Then the charger stops charging.

    Too much current, or too high a current, then you damage the battery or it catches fire.
    Not enough current, then it takes forever to charge.
    Not enough voltage and it doesn't reach full charge.
     
  7. Jul 18, 2015 #6
    The same article said that such a charge controller would take up a lot of power. Is there any information on exactly how much?
     
  8. Jul 18, 2015 #7

    meBigGuy

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    It's not good to reference articles without linking to them. It is very possible you are misunderstanding or mis quoting.

    Read this:
    http://www.digikey.com/en/articles/techzone/2012/sep/a-designers-guide-to-lithium-battery-charging [Broken]

    And then this:
    http://www.ti.com/lit/ds/symlink/bq2000.pdf


    The charger efficiency depends on how the charger is implemented. A linear current source (using a transistor to drop the voltage to the proper voltage to maintain the current) would waste power by the ratio of the source voltage to the battery voltage since all the voltage dropped across the pass transistor times the constant current would be wasted power. Chargers for other technologies have a similar issue if a wasteful linear controllers is used.

    A switching regulator is pretty efficient.

    As for the efficiency of the chemical process itself, I think it is pretty good in all cases since the battery doesn't heat up a lot, but I don't know the numbers off the top of my head.
     
    Last edited by a moderator: May 7, 2017
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