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Are 60w & 85w power adapters safe to use on MacBook Air?

I've seen internet postings on various sites saying that it's safe to use the 60w and 85w Magsafe power adapters with the MacBook Air (which comes with a 45w Magsafe power adapter). But I can't find any official statement from Apple confirming that this is so. Just curious if anyone can definitively confirm that it is indeed safe.

(I know the 60w and 85w Magsafe power adapters have a different form factor and that the MacBook Air can't sit flat on a surface if you use them -- I'm just curious if it's safe to use them on my MacBook Air.)

Thanks!

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well i have an old MBP needing 85W that will NOT work with 60W

i dont think that as mine is not backward compatible that the same mba - mac book air - of the same era would also not be compatable - it may work here n there temporarily but then damage the internal(s) of the machine as its designed to take less w-age - less wattage - NOT more or not 25W more then normal, however the only realy way to know is ... suck it and see some mac are different to other - i would not suck it an see id get a 60W as you dont want find it kills your mac if you try it its at your own risk.

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here's the definitive answer: YES, you can use a higher rated power adapter with your MBA (or whatever) with no ill effect.

see this KB article from Apple: http://support.apple.com/kb/HT2346

the power rating of the adapter is simply the maximum power that it can supply. the voltage of these adapters is all the same (I think around 18.5volts?), so it simply means the higher rated adapters are *capable* of providing higher current if necessary. some of the models require the higher current to charge their batteries, therefore those machines ship with higher wattage chargers. Your MB Air will just draw the same amount of current whichever adapter is used, as long as the minimum wattage is provided.

in the reverse case, if you use too low a wattage adapter (e.g. 45W one on a MB Pro), there won't be enough current to charge the battery, although you can run it off AC power while plugged in.

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Fantastic! The official word from Apple is what I was looking for and couldn't find. Thanks!

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The charger is a dual-voltage charger. It uses 16.5V for normal operations and switches to 18.5V for intensive tasks.

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It makes sense that you could use a higher wattage adapter on a lower wattage system if they were both the same voltage but the 85W adapter is 16.5/18.5 volts and the 45w adapter is a 14.5 volt adapter. I read the apple article and they say it is okay but I would like someone to explain why the voltage difference does not matter. Could it wear out your battery faster?

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Just for further information, the new MacBooks have the same angled connector as the MacBook Air, in 60 watts. So those are a direct fit with no angle awkwardness!

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This information isn't entirely true. I have been using a 45w adapter with my new mid2014 15" MBP for a couple of weeks. It will charge the batteries no problem so long as you're not doing anything power intensive. I expect that it wouldn't work for gaming, but for everyday use it's fine.

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With some testing, it is definitely safe for the charger if you are charging a macbook that needs more wattage.. The charger will never provide more than the rated wattage, and as such, there is no higher risk of failure.

On the other hand, if you use a 45w on your MacBook Pro, which requires an 85w charger while you are playing a game or editing video (using 100% CPU and/or GPU), your battery will still drain but at a must slower rate. I have read that if you let it reach zero, it'll keep on going and kill your battery as the voltage will go too low.

I personally use a 60w charger with my MacBook Pro Retina which comes with an 85w charger. It charges a tad bit slower but it's perfectly fine. Here are the screenshots:

In this image, I am using my 60w charger while low use (medium brightness, no CPU intensive tasks) but it is charging. It is only pulling 56.04 watts, well within the limits of the 60w charger.

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Here, I experimented with a 45w charger while I am stress testing with geekbench and full brightness, as you can see the charger is pushing out 40w, again, well within the limits. On the other hand, it is now draining the battery (but at a slower rate)

Block Image

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Another indirect evidence that it is OK to charge your MBA with an 85W magsafe is that the Thunderbolt Display has a magsafe cable that Apple claims can charge up to 85W for either MBP and MBA, suggesting that the display is outfitted with an 85W magsafe that can be used for a lower watt MBA. If that is true, I would deduce that you can use an 85W magsafe adaptor to also charge a MBA. I've just got a MBP and MBA and swap the adaptors depending on convenience (i.e. I carry only the 85W around and use it to charge either laptop), and no ill-effect. Just my 2-cents.

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So many explanations, but none cites simple technical point. As some mentioned, yes lower rated charger supplying higher load runs risk of burn out. Now, if apple makes "super quality" chargers which are capable of supplying to higher loads (although it would be surprising if thats true, as it increases manufacturing cost for usually unrealised "quality") thats a different story. If my charger is rated 60W I would NOT use it on a machine rated 85W. If someone did and didn't blow up the charger then s/he must be lucky, but its only matter of time before its toast. With that said, if the circuitry employs current limiters then you wont blow up the charger by using it on higher load, but it might well be incapable to charge battery at the rate its draining.

Chandrakanth.

Update

@Gabe, so it falls inline with expectations. It would charge slower. How long have you been using 60W on MBP? Did you ever try using your mac with battery charging from less than 25% while watching flash video with full screen brightness? (the idea is to draw max power).

If you did, and the charger is safe that confirms presence of current limiters which ensures safety. Thanks for sharing your experience.

-Chandrakanth.

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I use a 60w charger with my 15" MBPR everyday and it hasn't blown. It doesn't supply more than 60w of power so that's why it doesn't blow up. It just charges slower.

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Here's the 60w charger connected to my MBPR now, it's taking in 56.04 watts, less than 60, well within the capabilities of the charger.

http://cl.ly/image/1Y3n1W2v3x3o/Screen%2...

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Thanks, Gabe, for supplying some actual evidence -- you are about the only person replying to this question who has done anything other than state an unsubstantiated opinion.

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Here's a screenshot of me doing something even more extreme, a 45w charger while the CPU is running at 100% and brightness at max. As you can see, the charger is putting out 40w and my laptop is actually draining from the battery, but at a much slower rate. Once I stopped geekbench, I actually started to gain charge at 1748 mA.

http://cl.ly/image/0P242p0L2A0Y

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Awesome, that's great information! You should post this as an answer so we can vote it to the top! :-)

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How to Locate the Power Rating?

To find the right charger for Macbook ,there are three kinds of power rating Macbook power adapter in the market,45 watt, 60 watt, or 85 watt. It should be noted that higher wattage chargers can be used on the lower wattage laptops, but not vice versa.For example,If you have mac laptops that have used all three wattages. you could buy the 85w ones as my back up. Why? Because the 85w will work on any laptop, but the 45 and 60 will not. Further, the cost difference between the 45w, 60w and 85w is virtually nothing so you might as well “go big” and never worry if you have the right adapter for the right laptop.You can also find the Power Rating details on your orignal macbook charger and get the same Power Rating as your origanl macbook charger .

For More:http://goo.gl/1rNhIA

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85 W may use dynamic negative resistance, but be stable with load to provide variable voltage. Can use 60 W on 15" MBP which may be constant voltage, but battery will run down if using discrete display. Discrete display is required for external monitor or projector.

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A related issue - these macbook power supplies are 'class 1' They have two parts: the supply itself and a lead/plug that connects it to the mains/wall socket. The slotted bit that slides onto the supply has metal sides that make the earth connection to the round metal stud on the supply. That's fine however ipad/iphone power supplies use the same connection method except ipad/phone supplies are class 2 and don't have an earth. On the mains plug part that comes with these the slot is all plastic ie no earth connection is possible. The above macbook supplies will fit these just the same. They need an earth but they won't get one!!!!

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I bought a 60 watt charger for a 2012 15 inch Macbook Pro.. The white box is running so hot you could cook an egg on it. So, I need to get the higher rated one.

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Disable the WinVidia. Use built in Intel GPU.

With my mid 2010 the 60W runs fine. Takes a little longer to charge, but always charges.

The charging circuit should only pull 60W at the lower Voltage.

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I'm not sure this in an answer, but I'd like to note, that each and every of the three adaptors features different voltage.

If I used e.g. 19V instaed of 14,5 what could happen?

Nobody, including Apple, has explained this matter.

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mister790 will be eternally grateful.
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