Using a Voltage regulator

Discussion in 'The Projects Forum' started by MMH, Feb 21, 2013.

  1. MMH

    Thread Starter Member

    Feb 8, 2013
    143
    4
    Hello there!! I was just thinking whether i could make a Li-ion or Lead acid(not sealed-4.2v) charger using a voltage regulator(eg.LM317), or a timer(NE555). I have 2-4.2v Lead Acid Batts(Capacity unknown- Extracted from flashlights) and a 3.7v li-ion cell( Capacity unknown- Extracted from a mobile phone). As what I have Read Li-ion And Pb batts are charged by voltage(unlike NIMHs). Is it possible?:rolleyes:

    Any help will be greatly appreciated.and please dont forget to help me with these::)
    https://forum.allaboutcircuits.com/showthread.php?p=573597#post573597
    https://forum.allaboutcircuits.com/showthread.php?p=573595#post573595
     
  2. JMac3108

    Active Member

    Aug 16, 2010
    349
    66
    LiIon charging is more complicated than a simple voltage source. To fully charge a LiIon safely, you need a CVCC (Constant Current / Constant Voltage) charge algorithm. The voltage termination (4.2V/cell) is very critical.

    Also, LiIon batteries can be quite dangerous and you should not charge them unless you fully understand them.

    I'd suggest a google search on LiIon charging to get a little background before you consider designing a charger.
     
  3. DickCappels

    Moderator

    Aug 21, 2008
    2,648
    632
  4. MMH

    Thread Starter Member

    Feb 8, 2013
    143
    4
    Thanks for answering. What do you think about lead acids? Cant they be charged using Lm317? And what shall de the values of the resistors, transistors, etc if the required V is 5 and the V out is 9? Can a LM317 calc. help?
     
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