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How to charge a 7.5v battery from a mini-wind generator of 12v?

Discussion in 'Power Electronics' started by MEERA, Feb 16, 2014.

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  1. MEERA


    Jan 29, 2014
    im working for a project of charging mobile phone (5v,500ma) using wind generator (DC motor 12v)

    im using power bank battery of 7.5v 700mAh Li-On (Dump load) i need to charge this battery which is regulated to 5v for charging phone (output)

    i have almost completed this project:eek:

    but some issues are noted on working condition :(

    on testing wind generator with no load the voltage is around 10-15 v
    on connecting dump load in parallel , it shows voltage of battery only ... which shows no charging condition of battery:confused:

    the below circuit diagram may help u to understand better

    please solve me this problem and also tell me that this way of charging battery is correct or any other changes to be made in order to improve efficiency !

    Attached Files:

    • ckt.png
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  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    One should not charge a 7.5V Li Ion battery from a 10V source. Li Ion batteries are very sensitive to overchargeing read this discussion on proper charging techniques for Li Ion batteries.
    Where exactly do you connect the dump load? Show the connection in the diagram.
  3. MEERA


    Jan 29, 2014
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Sorry, that's a very poor circuit.
    Best case: your batteries will not last very long.
    Worst case: your batteries will catch fire.

    Read the articel I linked to. Google "charging li-ion batteries" for even more information. Use a dedicated Li-Ion charger IC.
  5. Arouse1973

    Arouse1973 Adam

    Dec 18, 2013
    Absolutely Harald. It is very very dangerous to do what you are doing. Lithium batteries generally require a constant current / constant voltage charging system. They start off with a constant current and finish charging with a constant voltage and when the current is about 3% of the maximum charge current they should switch off. The battery can not handle over charge and can catch fire.

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