87W Power adapter with Macbook

Discussion in 'MacBook' started by Mjb347, Nov 1, 2016.

  1. Mjb347 macrumors newbie

    Joined:
    Jun 11, 2013
    #1
    Planning on buying the 2016 MBP and already have a 2016 Macbook. Can I use the 87 power adapter with both even though the 2016 MB has a lower watt adapter?
     
  2. BeyondtheTech macrumors 68020

    BeyondtheTech

    Joined:
    Jun 20, 2007
    #2
    Like previous MacBooks and MacBook Pros, it will only draw the power it needs. Won't charge any faster, either, of course.

    In reverse, if you use the low-power adapter on the newer MacBook Pro, it will likely not have enough juice and ultimately result in a slower drain of the battery, as it's fighting to keep up with the draw that the MacBook Pro needs. If the MBP is in sleep mode or fully powered down, it will charge, but much more slowly than if you used the adapter it came with.
     
  3. speedbumpnv macrumors 6502

    Joined:
    Jul 2, 2007
    #3
    Do we have to worry about the larger MacBook over-drawing current through a charger meant for a smaller MacBook? Or will the chargers only deliver what they are rated for regardless of what the computer wants/needs?
     
  4. evec macrumors regular

    Joined:
    Jun 8, 2016
    #4
    Machine and Power supply have separated internal current (power)limits.
    For example 29W power supply only can delivery about 27W to the mac side whenever the mac need.

    The power supplied by adaptor will first supply to system, and remain power will supply to battery when need to change.
    So if you put a 29W in larger MacBook, if the system require more that 29W power (mbpr sometime may need 40W or above)
    , the system will get power from the battery, and recharge to battery when the system drain power lower that about 27W.

    USB-C power supply and device have additional communicating system, which two devices can get information from opposite and set suitable voltage/current limit.
     

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