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Discussion in 'Electronic Basics' started by leaky_caldron, Dec 15, 2003.

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  1. The AC/DC charger for my 15.6v cordless drill has stopped working.
    It's definitely the charger, not the base or the battery.

    I have been unable to source a replacement 18v,300ma charger. I've
    tried various outlets, including local DIY stores, Ebay and charger/
    adapter manufacturers sites on the internet. They all seem to have a
    maximum of 12v available. Obviously I don't want to pay through the
    nose for a charger that might end up costing more than a new drill!

    I have found an old, working US Robotics adapter from a modem. This is
    rated at 18V but delivers 500ma.

    What is the likely impact of using this charger to charge the drill
    battery?I've checked the polarity which is +ve on both, so the only
    issue seems to be whether 500ma is too high a charge to deliver to the
    battery who's original charger is rated 300ma (5 HOURS CHARGE TIME).
    Is it possible that the adapter base in some way limits the charge to
    300ma or would charging at proportionately less time at 500ma (3
    hours) be okay?

    Any ideas please?
  2. Louis Bybee

    Louis Bybee Guest

    This seems so elementary I'm almost afraid to ask, but have you tried the
    manufacture of the drill to see if a replacement charger is available?


  3. --
    Regards ............... Rheilly PhoullIf I understand what you are asking
    it's "Can I use a 500mA supply to replace a 300mA one to charge my drill
    (via the charging adaptor base)".
    IMHO it would be an improvement, since the wallwart would run cooler. The
    "base" sets up the current used and the wallwart only has to supply what the
    load requires.
  4. Only holds true if there is some regulating circuitry in the base. So far,
    I' ve seen several ones with nothing at all in them, just a direct
    connection to the wall wart (which relied on the transformer's internal
    resistance to limit the charging current). Since modem PSUs sometimes rely
    on the modem to do the filtering and regulation I would recommend first to
    check whether the accumulator heats up more than needed and (in this case)
    use a shorter charging time.

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