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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Notebooks > MacBook Power Adaptor: Diff between 60w & 85w?

MacBook Power Adaptor: Diff between 60w & 85w?
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Love Calm Quiet
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Jul 29, 2009, 05:10 PM
 
So my wife got white(plastic) MacBook just couple months ago, and we want a backup MagSafe Power Adaptor.

The ratings at Amazon suggest that both 60watt and 85watt frequently have mechanical/electrical issues.

Is it okay to use the 85watt model ("for MacBook Pro") with the MacBook?

Also one seller says theirs is: " GENUINE APPLE BRAND, Slightly larger version of Apple's, 85W AC Power Adapter." Anybody guess why an item could possibly be "slightly larger"? The refurb process? [I have trouble figuring how one of those could ever be refurbed anyway.]
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turtle777
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Jul 29, 2009, 05:12 PM
 
You can always use a HIGHER rated adapter w/o problems.

You might blow the adapter if you try to use a lower rated one.

-t
     
Love Calm Quiet  (op)
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Jul 29, 2009, 05:43 PM
 
Thanks. I was figuring that should be so...

I especially wanted to make sure that there weren't differing couplings into the different MBs.
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ghporter
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Jul 29, 2009, 05:51 PM
 
The MagSafe connector is the same. You can use the MBP's 85W adapter on a MacBook without any problem, but the other way around is not such a good idea. 60W is not enough to power an MBP and charge the battery, and maybe not enough to even fully power it if you're doing much at all. This can lead to problems...

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Big Mac
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Jul 29, 2009, 07:26 PM
 
Technically, Apple says that using a MBP adapter with a MB battery may artificially shorten the life of the battery by supplying an excess amount of power to it.

"The natural progress of things is for liberty to yield and government to gain ground." TJ
     
turtle777
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Jul 29, 2009, 09:00 PM
 
Originally Posted by Big Mac View Post
Technically, Apple says that using a MBP adapter with a MB battery may artificially shorten the life of the battery by supplying an excess amount of power to it.
Typical CYA statement.

-t
     
ibook_steve
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Jul 29, 2009, 11:45 PM
 
Originally Posted by Big Mac View Post
Technically, Apple says that using a MBP adapter with a MB battery may artificially shorten the life of the battery by supplying an excess amount of power to it.
Source? This makes no sense. An electrical system only uses as much power as it needs. The battery charging system is smart. It's not going to force extra power into the battery if it's available.

The "larger" mention in the ad refers to the size of the brick itself. The 85W adapter for the first couple of generations of MBPs was noticeably larger than the 60W. They now look exactly the same.

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Brien
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Jul 30, 2009, 12:17 AM
 
See, if Apple were smart they'd can the 45 and 60W adaptors and just sell the 85W and avoid the confusion.
     
Simon
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Jul 30, 2009, 03:28 AM
 
There's lots of FUD about this and a good portion of corporate CYA as turtle already pointed out.

• You can always charge any Mac with an adapter rated for a higher max output. It's the computer that determines how much the adapter should charge. The adapter has no problems delivering less than its max rating. Using a MBP charger with a MB will not damage the charger or the MB.

• You can also charge a higher power Mac with a lower power charger. The Mac might request more than the charger can deliver, but that's not really a problem for the charger; it simply won't output more than it's rated to do. And charging will simply take longer. Again, do not expect damage to either the charger or the Mac. But you definitely won't charge a MBP as fast with a MB adapter. Also, under heavy use it might no longer be sufficient to charge at all and all it will do is keep the MBP running. The extreme case is the 45W MBA charger used with a MBP. Under heavy load the MBP will draw more than the 45W the MBA charger can deliver. In such a case it will run down the battery even though you think you are charging. Worse yet, if no battery is inserted (bad idea anyway) or the battery is empty, the Mac could just shut off when its load peaks beyond the 45W the MBA adapter can deliver.

Summary: the very worst that can happen is that your Mac unexpectedly shuts off. This is a rare case though (MBP under peak load, MBA charger, no battery or empty battery). Beyond that, the only thing to worry about is charging speed. In any event, no damage will occur to the charger or the Mac.
( Last edited by Simon; Jul 30, 2009 at 03:34 AM. )
     
Simon
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Jul 30, 2009, 03:36 AM
 
Originally Posted by Brien View Post
See, if Apple were smart they'd can the 45 and 60W adaptors and just sell the 85W and avoid the confusion.
That would indeed be convenient, but it would cost Apple more money. That's the whole reason behind having multiple chargers.
     
Love Calm Quiet  (op)
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Jul 30, 2009, 07:11 AM
 
Originally Posted by ibook_steve View Post
The 85W adapter for the first couple of generations of MBPs was noticeably larger than the 60W. They now look exactly the same.
Steve
Thanks Steve - that was the most mysterious part to me.

Let's just hope that the construction quality on those earlier was no worse than most recent ones (which are bad enough, judging from recent Amazon review comments) - I decide to that one a whirl, being available at $10 less.

Thanks to everyone. I'll forgive Apple the confusion they provide... if they'll just up the lifetime/durability on both the brick and cord.
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Simon
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Jul 30, 2009, 08:19 AM
 
Originally Posted by Love Calm Quiet View Post
Let's just hope that the construction quality on those earlier was no worse than most recent ones (which are bad enough, judging from recent Amazon review comments) - I decide to that one a whirl, being available at $10 less.
I have one of those bulky 85W adapters for an original CD MBP sitting right here. It's in use pretty much 24/7. Right next to it is a modern 85W adapter charging a new unibody MBP. The latter is significantly smaller, but they both work just fine. Haven't had any problems with either. Not even the over three year old one. It's just plain bulky.
     
Love Calm Quiet  (op)
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Jul 30, 2009, 12:14 PM
 
Originally Posted by Simon View Post
I have one of those bulky 85W adapters for an original CD MBP sitting right here. It's in use pretty much 24/7. .... Not even the over three year old one. It's just plain bulky.
Gracias, Simon... this one'll just be for the desk, not travel, so that's good news.
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chabig
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Jul 31, 2009, 10:22 AM
 
Originally Posted by Love Calm Quiet View Post
Let's just hope that the construction quality on those earlier was no worse than most recent ones (which are bad enough, judging from recent Amazon review comments)
You should be fine. Online reviews are OK, but remember that generally speaking only people with problems post. This leads to the illusion that a product is rife with problems. I've had no problems with any of my 5 MacBook adapters.
     
   
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