Mains adaptor for MBP 13"

Discussion in 'MacBook Pro' started by costabunny, Oct 9, 2009.

  1. costabunny macrumors 68020


    May 15, 2008
    Weymouth, UK
    Well I am feeling a lot of love for my new 13" MBP, but I have a question:

    I still have a spare 85w Mains adapter and I'd like to be able to use it - my understanding (correct me if I am wrong) is that the MBP will pull the wattage from the mains so a larger one will do no damage. The Apple guy says he wouldn't recommend it (and hence tried to sell me a new 65w one).

    Is it safe for me to use the 85w one as my second mains unit? (I like to keep one upstairs and one in the lounge)?

    Little advice from someone who understands this wattage thing would be nice....
  2. rowsdower macrumors 6502

    Jun 2, 2009
    The watt rating indicates the maximum amount of power the adapter can provide. Both the 65w and 85w adapters provide the same voltage, which is what you need to worry about. So, it is safe to use either adapter with your MBP.
  3. shambo macrumors 6502a


    Apr 4, 2009
    I wouldn't use it myself for fear of my bad boy blowing. :eek:
  4. uberamd macrumors 68030


    May 26, 2009
    What he said.

    I wouldn't do it on my own laptop, but then again I have a 17" so using a 65w or 45w isn't an option. Just seems like it might have *some* unforeseen consequences.
  5. nanofrog macrumors G4

    May 6, 2008
    Assuming the 65 & 85W units are of the same voltage and MBP connector, you're golden. :D

    Only the deliverable current is different, and the computer will only draw what it needs. The higher rated unit should actually run cooler (presuming adequate heat sinking on the Voltage Reg's), and not be as stressed to provide the necessary load, as it's lower than it's rating. Not "force" a higher current through the computer, causing damage. The Apple guy apparently doesn't understand basic electricity as well as s/he thinks. ;) :p
  6. tofagerl macrumors 6502a


    May 16, 2006
    Unless something is actually wrong with either the lines in your house, the adapter or the machine, it's going to get the ~65W it needs, and not one...picowatt more.
    If something IS wrong with one of those three places, it would be wrong no matter what the specified wattage of the adapter was.

    In other words: Use a "larger" adapter if you want, but don't use a "lower", since it will either charge slowly or not at all.
  7. miles01110 macrumors Core


    Jul 24, 2006
    The Ivory Tower (I'm not coming down)
  8. costabunny thread starter macrumors 68020


    May 15, 2008
    Weymouth, UK
    thanks everyone - She is happily suckling electrojuice from the 80w and all is good :)

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