rMBP 13 charges faster with 85W Magsafe?

Discussion in 'MacBook Pro' started by scooby321, Mar 31, 2013.

  1. scooby321 macrumors newbie

    Joined:
    Jul 27, 2012
    #1
    Does the rMBP 13 charge faster with a 85 W Magsafe adaptor? Has anyone ever benchmarked?

    If I understand correctly, size difference between 60 W and 85 W is minimal but I could not find any information on weight difference. Any information would be greatly appreciated!
     
  2. justperry macrumors 604

    justperry

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    #2
    Most likely it will not charge faster, the Wattage is the maximum the Power Supply delivers, it does not mean it will deliver that much, it would not be good for a charger to be charging at 100% capacity.

    The Laptop is the one asking (controlling) for Power, so if it asks for 2 Amps it won't matter if the power supply can deliver 10 Amps.
     
  3. Stetrain macrumors 68040

    Joined:
    Feb 6, 2009
    #3
    I use an 85w charger with my 2008 13" aluminum Macbook. As far as I can tell the charging speed difference is negligible, but the charger does stay much cooler since it isn't being used at max capacity.
     
  4. justperry macrumors 604

    justperry

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    #4
    You confirmed what I was thinking, and yes it should stay cooler since the load is less.

    Thanks
     
  5. drambuie macrumors 6502a

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    Feb 16, 2010
    #5
    The one situation where the 85W charger could provide quicker charging than the 60W one, is when you are using the MBP at high CPU load while charging the battery.
     
  6. justperry macrumors 604

    justperry

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    #6
    You don't know, the MBP internal SMC might prevents higher charging, there is very likely to be a maximum Amp set so it won't matter.
     
  7. drambuie macrumors 6502a

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    Feb 16, 2010
    #7
    I know the maximum charging rate is fixed. I was referring to situations where the battery charges much more slowly, or even drains, especially with USB peripherals attached, if the MBP is being used at high load while charging.

    My 15" MBP charges a lot faster if powered off during charging. The 15" could probably do better with a 100W power supply.
     
  8. justperry macrumors 604

    justperry

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    #8
    Of course it will charge faster if off, then all the power from the charger is available for charging instead of half to the System half for charging, a 100 Watt charger would not do anything or very little as confirmed by Stetrain.
     
  9. dusk007 macrumors 68040

    dusk007

    Joined:
    Dec 5, 2009
    #9
    According to a thg article the 15" charges at 35W when off max and never more than 30W when on.
    The 13" has a few cells less so it is probably a little less. Everything past that it won't do because the battery pack doesn't like to be charged too quickly. Afaik it is always a bit of a tradeoff between longevity and fast charging. Or was it capacity. Anyway usually how fast a given battery is supposed to be charged is limited. You can always charge lower but not faster, at least it ain't smart to do.
    Between 80 and 100% the charge rate sinks dramatically. Once it is mostly full it needs less.

    If the supply can deliver those 30W on top of what the machine consumes while you are using it, charge rate will be as good as it can be.
     

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