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Making MP3 Player capable of charging batteries

Discussion in 'Power Electronics' started by syrevo, Dec 3, 2013.

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  1. syrevo

    syrevo

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    0
    Dec 3, 2013
    I'm trying to convert non-chargeable mp3 players into charger and mp3 player at the same time so the user can simply plug the mp3 into any USB to charge his battery

    To lower the cost of converting as much as possible my idea is to use a 2.4v zener diode (the device hold 2x AAA batteries) connected between the USB connector positive pin and the battery positive pole.

    My question is since the device will try to charge the batteries constantly as long as it's connected to USB (5V - up to 500mhA) will that setup harm the batteries if left for a long period of time and is there any other options?

    I'm thinking about using Ni-Ca batteries since Ni-Ca can endure overcharge better than Ni-Mh and Lithium
     
  2. davenn

    davenn Moderator

    13,765
    1,920
    Sep 5, 2009
    hi there
    welcome to the forums :)

    a zener isn't connected in series like that
    have a look at this Wiki Page and scroll down to Uses
    to see there is a current limiting resistor in series and the zener is in parallel with the load

    cheers
    Dave
     
  3. syrevo

    syrevo

    2
    0
    Dec 3, 2013
    Thank you for your reply

    I see, so i need to add a resistor. is 5.6 ohm good for the circuit?
     
  4. davenn

    davenn Moderator

    13,765
    1,920
    Sep 5, 2009
    from that page ......

    The diode wattage rating will also need to be chosen to handle the current

    Dave
     
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