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How do I build a simple charger for 3 or 4 LI-Ion cells ?

Discussion in 'Power Electronics' started by enocknitti, Aug 24, 2021.

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  1. enocknitti

    enocknitti

    3
    0
    Aug 24, 2021
    I have a number of 18650 Li-Ion cells I want to use in some home-made stuff.
    What I want to build is a charger for the cells. Input is 12-18 V. Preferably something that can be built-in.
    I need overcharging protection, deep discharge protection I can do without..

    Any suggestions ?
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,667
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    Nov 17, 2011
    Do you want to use the batteries single or in combination (parallel or serial connection)?
    For single use, you can buy inexpensive charger modules (example) that operate from 5 V, so you'll need an additional step-down module (also not expensive. Example) to create the 5 V from 12 V ... 18 V. These charger module are used to build a 5 V power bank from the Li-Ion battery.
    For a parallel connection of the batteries the same setup can be used. But paralleling Li-Ion batteries bears a certain risk, read e.g. here.
    For a series connection you will need a charger with charge balancing to ensure long life of the battery pack.
     
  3. enocknitti

    enocknitti

    3
    0
    Aug 24, 2021
    I need series connection.
     
  4. Bluejets

    Bluejets

    5,001
    1,050
    Oct 5, 2014
    How many in series..??

    Here is one for 3S, couple of dollars just about antwhere online.

    3S1P.jpg
     
    Last edited: Aug 24, 2021
    Harald Kapp likes this.
  5. Harald Kapp

    Harald Kapp Moderator Moderator

    11,667
    2,700
    Nov 17, 2011
    Note the connections at B1 and B2? These are for charge balancing.
     
  6. enocknitti

    enocknitti

    3
    0
    Aug 24, 2021
    Thanks for your info. With the help of your image and goggle image search I was able to find a seller in EU.
     
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