Mobile charger as Ni-MH charger

Discussion in 'General Electronics Chat' started by Arup, Apr 13, 2006.

  1. Arup

    Thread Starter New Member

    Apr 13, 2006
    I've a LG mobile phone fast desktop charger lying around with the following ratings
    input 12V, 0.3A
    output 4.2 V 0.5
    it has 3 pins at the output, the battery fits into a slot over it and has a bicolour LED for charge indication (red - charging, green - done)
    the circuit consists of 3 ICs
    K1A494AP - PWM controller
    LM358N - OP AMP
    GMS81C1102 - 8 bit CMOS microcontroller.

    My question is can this charger be used as a Ni-MH charger after modding the output voltage to 1.8/2.0 V.
    also what is the function of the third pin on the charger and the battery?

    Thanks and regards
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
    best answer is: maybe
    it depdends on the circuit.

    the third pin is usually connected to temperature sensor.
  3. paultwang

    Well-Known Member

    Mar 8, 2006

    A quick note: Your phone charger probably recharges a lithium ion battery. I am not sure if you can apply the Li-ion recharge pattern to NiMH batteries.
  4. Gadget

    Distinguished Member

    Jan 10, 2006
    Thats pretty much the way I understand it as well. Not 100% on LIon charging, but I think is a constant voltage charge (4.2v per cell which would tie in with your figures) and Charge detection based on a drop off in current.
    NiMH however (like NiCads) use a constant CURRENT charge with detection using either a slight drop in cell voltage at full charge, or the rise in cell temperature. I believe NiMH also like a fast charge.