Replacing a Broken Higher Voltage AC Adapter for Cordless Drill

Hi All, need help please:

I have a cordless 909 drill and the AC adapter on the removable battery charger unit has died. I'm having a hard time finding a replacement universal adapter due to the higher voltage (18V) and unusual tip size.

Specs of the broken charger:
OUTPUT: 18.0V, 0.4A DC

An option I can find at that voltage are universal "laptop" chargers on eBay
e.g. this, which has a much higher current out at 18V: 4.5A eBAy link

Is there something different/special about AC adapters labelled "laptop chargers" which would make this unsuitable to replace the broken "wall-wart" adapter?

Jaycar has a universal adapter for $35 (more than drill cost new!) so that is my last option but would prefer not to have to go down that route.

Thanks, any help appreciated

Comments

  • +1 vote

    What sort of battery is it? Is it NiCad or Ni-Mh or Li-ion? Did the old adapter trickle charge when full or do you need to unplug it after you charge it overnight?

    •  

      Battery is Li-ion

      The unit is from this old Masters deal:

      I actually have no idea about the charge time, I bought it 2 years ago and the unopened box was thrown into the cupboard. I've just opened it and the adapter died on the first use. Lesson learned: open everything the day you get it and make sure it works!

  • +1 vote

    Assuming that the old adaptor was just a dumb adaptor, all the charging regulatory circuitry should be in the drill, charging plate, or battery itself. By describing as a wall wort, I am assuming it is simple power adaptor.

    You should be fine replacing with any 18V adaptor that has the correct jack (or correct swappable jack). Failing that you could try to splice the old jack to the new cord (would be last resort).

    As far as I am aware, as long as the amperage of the adaptor is at least as much as the old adaptor, you should not have any issues (think of it as 18V at 'up to' 4.5A). The charging circuitry should regulate the amperage being pulled.

    I did some research a while back when I replaced a broken DC adaptor for the alarm system that came with the house with a higher amperage but same voltage adaptor and haven't had any issues.

    •  

      Thanks, helpful advice!

      The charging circuitry should regulate the amperage being pulled.

      That's what I am hoping but have no experience and don't want to deal with an exploded battery…

      •  

        As long as the voltage is correct Amperage rating is just the maximum possible.

        Definitely nothing to worry about there.

  • +1 vote

    The higher current is fine. Voltage needs to be the same though. Output same as well. DC to DC. The battery will draw the amount of current it needs.
    Be careful if it is Li-ion battery. Over charging them can cause them to explode. If it is, charger should be made for Li-ion to prevent overcharging.

    •  

      If it is, charger should be made for Li-ion to prevent overcharging.

      Yup that's what I'm worried about as the battery is Li-ion but the drill is a cheap one - especially with the 10x higher amp output of the laptop charger.

  • +1 vote

    Higher Voltage AC

    18V is low DC Volt.

    • +1 vote

      Yeah sorry, what i meant is it's a higher voltage than almost all cheapie universal AC adapters, which seem to max out at around 12V DC output.

  • +1 vote

    Should be fine.. Buy the UK plug version $6.99 vs $18.98!

    The only other thing you need to consider is the polarity, centre positive or negative?

    Have a look for one of these symbols on the 909 charging dock or on the old plugpack
    https://en.wikipedia.org/wiki/Polarity_symbols

    •  

      The only other thing you need to consider is the polarity, centre positive or negative?

      Cheers, yes I think the laptop charger I linked to has the option to do either centre + or - by reversing the orientation of the tip

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