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Trickle Charge Batteries

Discussion in 'Power Electronics' started by spike1947, Feb 21, 2016.

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  1. spike1947

    spike1947

    23
    1
    Feb 4, 2016
    Hi

    I am wanting to know how I can rig up a simple trickle charge for 4 x AAA Ni-MH Rechargeable Batteries .I need them to run a 5 volt laser for a security set up I am making .

    cheers

    spike
     
  2. cjdelphi

    cjdelphi

    1,096
    104
    Oct 26, 2011
    How simple? 4 x 1.2v = 4.8v

    Get an adjustable regulator, set 4.8v and stick a resistor on it to trickle charge..

    I've never been too sure about charging cells in series, but i think nimh cells don't mind too much
     
    spike1947 likes this.
  3. Arouse1973

    Arouse1973 Adam

    5,164
    1,081
    Dec 18, 2013
    LM317 as a current source, used this for years charging 7.2 volt NIMH, with no probs.
    Adam
     
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  4. Colin Mitchell

    Colin Mitchell

    1,417
    312
    Aug 31, 2014
    But you haven't told him what input voltage he needs.
     
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  5. spike1947

    spike1947

    23
    1
    Feb 4, 2016
    Hi cjdelphi

    I don't want to buy a regulator I want to build my own ! .

    cheers

    spike
     
  6. BobK

    BobK

    7,682
    1,686
    Jan 5, 2010
    You can charge them forever at C/20. Any higher and it gets complicated.

    Bob
     
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  7. cjdelphi

    cjdelphi

    1,096
    104
    Oct 26, 2011
    A couple of transistors and a sense resistor for current regulation? Cheaper and quicker if you buy an lm317/resistor

    Substitute the 10ohm resistor for a value that trickle charges your battery... i selected 10ohm as it sounded reasonable to charge your batteries, just provide the circuit a higher voltage than your battery total voltage
     

    Attached Files:

    spike1947 likes this.
  8. BobK

    BobK

    7,682
    1,686
    Jan 5, 2010
    All that is needed is a voltage source significantly higher than the batteries full charge voltage and a resistor. The resistor should be calculated to drop (Vin - Vbatt) at a current of C / 20.

    This will cause a higher charging current when the battery is depleted, which is okay, going down to the C/20 current when the battery is fully charged.


    Bob
     
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  9. spike1947

    spike1947

    23
    1
    Feb 4, 2016
    Thanks guys , very helpful I now have all the info I need to crack on .

    cheers

    spike
     
    Arouse1973 likes this.
  10. Alec_t

    Alec_t

    2,892
    776
    Jul 7, 2015
    As explained on the other forum, you need a supply to handle the laser current plus a trickle charge.
     
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