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Traic does not turn off on 12V charger

Discussion in 'Electronic Design' started by George Jefferson, Jun 30, 2010.

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  1. I have an industrial strength 12V charger. Initially it would not turn off
    on battery removal. Replaced the triac and now works 95% of the time but in
    some cases it still does not turn off.

    The way it works: Controller triggers triac to supply charging power(from
    transformer). The controller senses the voltage from the battery to
    determine how to charge the battery(full charge, "trickle", etc...).

    Either the controller is bad(not turning off the triac), the triac is bad,
    or the circuit used is not well designed for the application(and/or designed
    for a specific triac).

    Again, what happens is when the cables to the battery are disconnected the
    controller stays on instead of turning off as normal(and again, does not
    happen most of the time).

    Simply because of the sparking involved when removing the battery cables it
    is obviously inductive(obviously because of the transformer). I believe
    that a snubber is probably in order(not sure if the controller has one
    and/or is bad/weak).

    Any other obvious possibilities that I'm overlooking?
  2. Grant

    Grant Guest

    One is supposed to turn off the power before disconnecting battery to
    avoid sparks which my ignite the explosive hydrogen given off during

    Try Jan's suggestion, but I'd use a lower value resistor, maybe 220 or
    less, to quench any snubber circuitry.

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