85W vs 65W Ac Adapter

Discussion in 'MacBook Pro' started by bennygoodx, Mar 23, 2009.

  1. bennygoodx macrumors newbie

    Joined:
    Mar 17, 2009
    #1
    Hey guys- I couldn't find anything when I searched that answered my question.

    I have a new MBP and an older MB. Curious what would happen, if anything, if I accidentally connected the wrong power supply to either computer.

    I have both of these next to each other on my desk....

    Thanks,
     
  2. jonbravo77 macrumors 6502a

    jonbravo77

    Joined:
    Feb 20, 2008
    Location:
    Phoenix, AZ
    #2
    Let's see, there is this thread that answers some of the question:
    http://forums.macrumors.com/showthread.php?t=670367&highlight=65W+vs+85w

    And then there is this thread that will probably finish answering your question:
    http://forums.macrumors.com/showthread.php?t=390967&highlight=65W+vs+85w
     
  3. Patriks7 macrumors 65816

    Patriks7

    Joined:
    Oct 26, 2008
    #3
    Try it to see some awesome fireworks! :cool:





    Nah, joking. Nothing bad should really happen. Big thing you will notice is that your MBP will take even longer to charge.
     
  4. TEG macrumors 604

    TEG

    Joined:
    Jan 21, 2002
    Location:
    Langley, Washington
    #4
    You could find your answer by searching, but I will help.

    If you plug the MBP wire into the MB, it should work fine, as the converter will modulate for what ever power is needed. As for the MB to MBP, that may cause problems, or it may work fine, depends on the load, although it is almost guaranteed that the battery won't charge.

    TEG
     
  5. belvdr macrumors 601

    Joined:
    Aug 15, 2005
    #5
    If you use the 65W when 85W is required, you will pull more power through that charger. The charger will get hotter and hotter, and could eventually start a fire. I learned this when a colleague plugged a 65W adapter into a docking station that required 95W.
     
  6. kenned macrumors member

    Joined:
    May 16, 2008
    Location:
    Denmark
    #6
    If you plug in the 65W adapter and the computer needs 75W, it will drain the extra 10W from the battery untill it is empty, and then crash to prevent damage to the system.
     
  7. belvdr macrumors 601

    Joined:
    Aug 15, 2005
    #7
    I don't believe laptops have that sophisticated of a charging system. It's either all AC or all battery, not a combination like some UPS systems can do. Why would a system crash to prevent damage? That's not really making any sense.

    The system will attempt to pull the entire 75W through that adapter, generating tons of heat.
     
  8. alphaod macrumors Core

    alphaod

    Joined:
    Feb 9, 2008
    Location:
    NYC
    #8
    The 85W adapter is auto-switching meaning it supports both 60W and 85W. When you plug in the MacBook, it will deliver 60W and when you plug in the MacBook Pro, it will delivery 85W; that said, I don't understand why anyone would buy the MacBook only 60W adapter. They are the same price and the 85W adapter runs cooler when only delivering 60W.
     
  9. belvdr macrumors 601

    Joined:
    Aug 15, 2005
    #9
    Auto-switching on an AC adapter means it will switch between 100/200V depending on the voltage at the outlet.

    The power rating is the maximum it can deliver, so there's really nothing switching in the circuit to provide that power. Same holds true for DC power supplies in ham radio. ;)
     
  10. kenned macrumors member

    Joined:
    May 16, 2008
    Location:
    Denmark
    #10
    This is what i've heard.

    And i don't believe a computer is damaged just because the power is cut off, why would that be a problem, except for damage to data ofc.
     
  11. belvdr macrumors 601

    Joined:
    Aug 15, 2005
    #11
    It would be just logical issues. However, if the system is that smart, it should be smart enough to shutdown gracefully before time runs out.
     

Share This Page