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Charge battery

  1. Aug 23, 2014 #1
    Please if we charge battery with high voltage like the battery charge voltage 4.2v and we supply 5v, is that will reduce the battery life.
    Thank you
  2. jcsd
  3. Aug 24, 2014 #2


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    Hi Kussy. Welcome to the Physics Forums.

    Almost certainly it will. To charge lithium cells with such excess voltage is dangerous. You have no idea what current this would force into the cells. Rechargeable cells are an expensive investment, you should buy the proper charger to maximize their performance and life. They need both voltage and current carefully controlled. Incorrect charging can imperil your safety, and that of others, and risk your home.

    There is another thread with specific details. https://www.physicsforums.com/showthread.php?t=767178
    Last edited: Aug 24, 2014
  4. Aug 24, 2014 #3
    Thank you for your reply NascentOxygen I will read more,
  5. Aug 24, 2014 #4
    My idea to use converter from AC-DC and use anther converter DC-DC to get the right voltage and current to charge Lithium-ion Battery (5 batteries Batteries on the parallel link) and covert the 3.6V to 12V to supply it for fan blower, I don't have much experience with electronic I need help with that
  6. Aug 24, 2014 #5
    What's your AC source? If you're going to grid connect this thing then buy a thoroughly tested, professionally built solution instead of building your own, otherwise there's a very real chance you might be exposed to a lethal electrical shock.

    Also, unless you know what you're doing, you shouldn't be connecting lithium-ion batteries in parallel. It's very easy to damage your batteries this way, and worst-case scenario you'll start a fire (possibly when you're not around to do something about it).
  7. Aug 24, 2014 #6
    Thank you Milesyoung for your advice, according to the data sheet of the Lithium-ion Battery show that over charge will cause no fire no explosion and because I don't have much space and wight and need for high capacity I think the Lithium-ion Battery is perfect for me and the data sheet for battery
  8. Aug 24, 2014 #7
    Let me just again emphasize that you shouldn't grid connect anything unless you have experience in designing for high-voltage applications.

    Your batteries might not explode or catch fire, but that isn't really a good indicator of performance. If you need more current from your lithium-ion battery, then buy a preassembled pack where the cells have been carefully matched - these also usually include some degree of protection circuitry. Even if you have a bunch of batteries of the same model the chances are high that they have different discharge characteristics.

    Have you considered just buying a 12 V battery pack and charger?
  9. Aug 25, 2014 #8


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    If this is true then you really should not start gaining electronics experience with a project like this. Whatever you may have read, elsewhere, take the advice from PF and use a commercial charger or you risk damaging your expensive Battery and, possibly, yourself. Buy one and you know just how much it will cost you. Save up your pennies for one.
    Learn about electronics, starting with simple audio amplifiers and flashing light projects. Electronics is a field that requires a lot of basic ground work before you launch out on clever stuff.
    If you don't want to believe me then see what DIY construction project kits are available. I very much doubt that you will find Lithium Battery chargers amongst them. There's a good reason for that.
  10. Aug 25, 2014 #9
    If I understand your question correctly: Of course; it's also fairly dangerous. There are voltage ratings for very good reasons.
    Last edited: Aug 25, 2014
  11. Aug 25, 2014 #10
    Hmmm...seems like some fairly advanced stuff you're wanting to do here; especially if you have little experience in electronics. I would suggest finding something already made and start with something...erm...more...appropriate...for your skill level.
  12. Aug 25, 2014 #11


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    Thread is closed for being too dangerous of a discussion, based on the OP's lack of experience.

    @Kussy -- Please seek help with a local expert who lives near you. You need to learn a lot more about electronics before you try to work on projects that can catch fire it you do them wrong.
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