magsafe power adapter question

Discussion in 'MacBook Pro' started by zamboknee, Mar 2, 2015.

  1. zamboknee macrumors regular

    Aug 10, 2009
    I have a 2008 Macbook Pro (15") that I've got about 2 additional power adapters for situated at various locations. I JUST bought a brand new 15" Retina Macbook Pro and would like to reuse the power adapters on it.
    Is this possible?
    Physically the magsafe plug won't fit but isn't there an adapter out there?
    What's the wattage restrictions on this?

    MacBook Pro with Retina display, OS X Yosemite (10.10.2), 2.5ghz, 15 inch
  2. kage207 macrumors 6502a

    Jul 23, 2008
  3. rctlr macrumors 6502a

    May 9, 2012
    I asked the same thing at the apple store.

    I had an 85w magsafe power supply, and wanted to use it with the magsafe2 adapter to my mac book air.

    The Air uses a 45w supply, and was told that even though it would work, they do not recommend it as the magsafe connector and magsafe2 adapter would heat up, and possibly fail, damaging the port. This is because of the large gap between wattages.

    So I decided against getting one.

    If the wattage is a lot closer, then Im sure it would be a lot better.


    Looking it up the new 15" has an 85w Power Supply.
    The 2008 also has a 85W (18.5V 4.6A), so my comments above are moot.

    A magsafe/2 adapter will certainly do the trick.
  4. zamboknee thread starter macrumors regular

    Aug 10, 2009
    Cool. So basically as long as the wattage is the same it should be fine, right? (after magsafe adapter, of course)
  5. snaky69 macrumors 603

    Mar 14, 2008
    Whoever told you this is full of it and needs to get his information correct.

    The computer draws what it needs from the magsafe, the magsafe doesn't push power into the computer. Even with a 85W adapter, a MBA will only draw 45W from it, with no additionnal heat generated.
  6. Richdmoore macrumors 68000


    Jul 24, 2007
    Troutdale, OR
    Exactly right. Here is an article direct from apple about using higher wattage power supplies with lower wattage devices. (It also mentions the MagSafe 2 adapter.)

    Power adapters for Intel-based Apple notebooks are available in 45W, 60W, and 85W varieties. Although you should always use the proper wattage adapter for your Apple notebook, you can use an adapter of a higher wattage without issue.
    For instance, if you have a MacBook (13-inch Late 2009) that normally uses a 60W adapter, you can also use an 85W adapter with that computer. You would not use a 45W adapter with that computer; it would not provide enough power for that MacBook.

    If you use a MagSafe 1 to 2 adapter, I would consider getting a MagSafe cozy adapter, just so you can keep from losing the small adapter.
  7. zamboknee thread starter macrumors regular

    Aug 10, 2009
    Is this an 85w adapter?

    Attached Files:

  8. snaky69 macrumors 603

    Mar 14, 2008
    Power (Watts) = Voltage (V) x Amperage (A)
    18.5V times 4.6A = 85.1W.

    Yes, it is an 85W adapter.
  9. rctlr macrumors 6502a

    May 9, 2012
    Thanks for that. That info came from an Apple Staff member at White City, London.
    Makes no odds now, I sold the spare 85w charger on Ebay now.

Share This Page