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battery charging

Discussion in 'Electronic Basics' started by Ken O, Jul 7, 2006.

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  1. Ken O

    Ken O Guest

    Hi

    I have been looking at schematics for battery charger. All the circuit I
    have seen so far seem to stop the charging to the battery from the source.
    most of them uses a pnp transistor to bypass the charge battery , therefore
    creating a link from the source + to ground.
    http://www.aaroncake.net/circuits/charger1.htm
    Anyhow, the battery voltage will eventually decrease, and the charger will
    go again , and again ....
    How would i go about it so that the charger don't start again.

    thanks

    ken
     
  2. Jamie

    Jamie Guest

    use an SCR in series with the output?
    using a current pulse sensor when you put the
    dead battery on line should be used to auto switch
    the SCR on. or use a m-pushbutton switch.

    Scr's will hold in the on state until the current
    being past drops below its holding spec.
    thus if you put the + on the anode side and use
    the cathode as the output and switch the SCR via
    the gate when you want the charger to start you will
    be all set.
    i've seen this type of charging switch used in many
    cases where you don't want the charger to come back
    on.
     
  3. Rich Grise

    Rich Grise Guest

    You could do this with a relay. Wire it such that the "start" switch pulls
    in the relay, which provides power to the charger. Also, pick off that
    power and supply the relay coil in parallel with the switch (maybe with
    isolation diodes). When the charger finishes its cycle, use that signal
    to open the lead to the relay, which drops out and removes power until
    you press the start switch again.

    Good Luck!
    Rich
     
  4. ehsjr

    ehsjr Guest

    The circuit shown on that page will never shut off
    current to the battery completely. There is a path
    from the 18 volt supply through R1 (500 ohms) and
    R7 (.2 ohms) to the battery, regardless of anything
    else that happens.

    I guess the designer's idea was this: The ~8 mA through
    that path, once the battery is fully charged, should make
    up for any self discharge, keeping the battery at full
    charge.

    Ed
     
  5. Ken O

    Ken O Guest

    Yes , this is why I am looking for a method the the charger will not come
    back on once the battery is charged.

    ken
     
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