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transisor sl100

Discussion in 'Homework Help' started by domz15, Aug 5, 2011.

  1. mvs sarma

    mvs sarma Well-Known Member

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    It is NOT the battery but the charger controller that has/would have the facility to stop further charging.
     
  2. domz15

    domz15 New Member

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    and that charger controller is inside the cellphone?
     
  3. mvs sarma

    mvs sarma Well-Known Member

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    For example, please see the microchip device
     

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  4. dave

    Dave New Member

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  5. domz15

    domz15 New Member

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    i can't understand it :(
     
  6. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Why don't you read about Lithium batteries at The Battery University (on the internet)?????

    A lithium battery charger requires a circuit that detects when it is fully charged. The detection circuit must stop over-charging to prevent the battery from catching on fire.
     
  7. Ziddik

    Ziddik Member

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    hi domz..

    Here is a typical charger circuit without using any transistor but a regulator ic for external DC power IN

    [​IMG]
     
    Last edited: Aug 13, 2011
  8. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The charger that Ziddik posted is for an old fashioned Ni-Cad battery and will cause a modern Lithium battery to explode or catch on fire.
     
  9. Ziddik

    Ziddik Member

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    i use this circuit to charge a 3.7v cellphone battery and it works perfectly
     
  10. domz15

    domz15 New Member

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    is that circuit automatically cut off the charging process when fully charged?
     
  11. alec_t

    alec_t Well-Known Member Most Helpful Member

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    No! It doesn't prevent over-charging, with the risks that Audioguru has pointed out plus the likelihood of a very short battery life. DON'T USE IT if your phone has a lithium battery (even if Ziddik does)!!.
     
  12. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Ziddik never said what is the type of battery in his cell phone. Lead-acid? Ni-Cad? Ni-MH? Lithium?

    Don't all modern Lithium cell phone batteries have a 3rd contact for the thermistor inside?
    Ziddik's "charger" does not use it.
     

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  13. Ziddik

    Ziddik Member

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    I use nokia bl-5c n will take 2 or 3 hours to fully charge my battery, I use it for a long time n still my battery is good..
     
    Last edited: Aug 14, 2011
  14. mvs sarma

    mvs sarma Well-Known Member

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    there are some chargers in society sold by China( see link http://www.amazon.com/Universal-Mobile-Phone-Battery-Charger/dp/B001AHU6QU )
    These have two adjustable leads and nothing more other than mains connecting pins on the other side
    the clip is pressed and battery with proper polarity is placed inside.
    For universality, the pins are to be adjusted to make contact with battery terminals.
    Audio guru may wonder that this item is sold on amazon.com

    so the thermistor etc are not cared, even though it was incorporated for safety.

    As such perhaps Ziddik might also be using his charger.

    No doubt that these chargers are highly dangerous and the battery might explode.

    yes we heard cases of Chinese batteries sold as replacements exploding.
     
  15. audioguru

    audioguru Well-Known Member Most Helpful Member

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  16. domz15

    domz15 New Member

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    My professor changed my project, She wants me to have a cellphone battery indicator instead of automatic cut-off.. Do you know a circuit of battery inidicator?
     
  17. audioguru

    audioguru Well-Known Member Most Helpful Member

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    What do you want to indicate? The battery temperature? The battery voltage?
     
  18. crutschow

    crutschow Well-Known Member Most Helpful Member

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    There is no way to accurately determine the charge on a lithium battery, expect by monitoring the amount of charge into and out of the battery, since Li battery voltage is not a reliable indicator of its state of charge. There are ICs designed to monitor the battery charge flow just for that purpose.
     
  19. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Since all cell phones have a battery charger circuit inside then you can make an indicator that the lithium battery is fully charged by monitoring its charging current. When the battery is fully charged then the charger IC disconnects the battery from the charger so the charging current becomes zero.
     
  20. domz15

    domz15 New Member

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    what IC it is?
     
  21. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Almost every semiconductor manufacturer makes a lithium battery charger IC. But I don't know which manufacturers are available in your country. Maxim make some good ones.
     

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