Using a Voltage regulator

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

  1. MMH

    Thread Starter Member

    Feb 8, 2013
    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::)
  2. JMac3108

    Active Member

    Aug 16, 2010
    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


    Aug 21, 2008
  4. MMH

    Thread Starter Member

    Feb 8, 2013
    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?