From what I can tell, the consensus seems to be that you can safely use the 85w MacBook Pro power adapter with the MacBook Air. Here is an Apple article (HT2346) that seems to me to suggest that it's okay to use the 85w with the MBA:All that said, I have not used the 85w with the Air. Because most of my work is done at a few different desks, I ordered extra 85w adapters for my 17' MacBook Pro (one for the bag/travel, one for desk one, one for desk two). The thing that bothers me (with respect to using the 85w adapter with the Air) isn't thewattage rating (85w) being higher than the Air adapter's 45w, or thecurrent rating being higher-but, specifically, the highervoltage rating does concern me.I understand wattage equals voltage times current. It has been my understanding that, in general (assuming tips match), that the use of higher current adapters with devices requiring lower current is okay, as long as the voltage matches. That is, I'm of the understanding that, in general, a 2-amp, 5-volt adapter should be fine with a device (for which the tip polarity and size match) requiring a 0.5-amp, 5 volt adapter. So, then, my specific issue here is that the decal on the outside of the 85w adapter does not show it auto-matching voltages down to 14.5v, only 18.5v and 16.5v.I also read this:I understand my concerns may be completely without merit-electricity and power adapters are not my areas of expertise.
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If my concerns are without merit, though, I'd appreciate someone explaining why.I've already purchased three extra 45w adapters for my late-2010 MBA 13'. Even then, as much as I move around, it'd be great to put one or two of the 85w adapters into service for the MBA so that I have plugs at the ready atany of the spots I work at in two different buildings. I just bought a 11' macbook air and have been using it at work using the 85W magsafe from my MBP (which is now sitting at home.I have no desire to bring it out anymore. The new air is simply powerful enough for everything I do at the lab)Uh, sorry, got distracted.Please note that the wattage specified by Apple is the 'MAX' wattage output. This and the input voltage are specified by Apple. Now, the 'ACTUAL' wattage being put out depends on how much current your device draws. So when I plug the 85W magsafe into my MBA, it'll draw AT MAX 45W and that's it, simply because the design in the charing circuit in the MBA does not draw more than that.This is also why using the 85W magsafe on my MBA won't make it charge any faster.If you do what I've been doing and your MBA ends up dying it's because of other reasons, such as a power surge (you are using a surge protector, right?).
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I can confirm that using the slightly higher voltage chargers intended for other Macbooks works fine on a Macbook Air 11' (Late 2010.) The Macbook Air wants 14.5 volts but charges properly on an adapter supplying 16.5 volts.I ordered a 3rd-party car charger by PWR+ to PWR+ product on Amazon that is intended for a MacBook Pro and nominally outputs 16.5V at about 60W instead of the 14.5V 45W output. It charged my MacBook Air properly using the car's 12V supply; the LED of the magsafe connector glowed yellow while charging and green when complete, and the menu bar charge indicator showed '100%'.See here to Apple Support article for complete morphology of Apple Magsafe adapters.-Steve. Just for safety reasons and protecting your device, I wouldnt risk it because of the voltage output difference between the two adapters. Although I have tried using the 60W adapter for MBP13' on my MBA.The only people that can answer this would be the engineers who designed the macbook air. There is probbably a voltage limiter of sort in the macbook that prevents higher voltage from entering the device.
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The cable came out of the MagSafe plug on my MacBook power supply, so I ordered a replacement cable. This is how to crack the power supply open and fit it, no need for a Dremel or a knife. You can replace the cable on your apple magsafe charger, if the cable is frayed, not charging, or cut. This method will work on magsafe 1 and 2 all wattage. There are different models of the same.
Otherwise, the higher voltage will eventually damage the laptop. Unless this is answered, I wouldnt risk it.
I'd rather carry the extra adapter if I need to rather than have a broken laptop.Message was edited by: rsannie. Actually, the question is still not answered - and I am wondering too.' Power adapters for Intel-based Apple portables are available in 45W, 60W, and 85W varieties. Although you should always use the proper wattage adapter for your Apple portable,.you can use an adapter of a higher wattage without issue.' This does not mention using an adapter of a higher voltage.
Voltages are much more important than wattages, as you can easily blow out a piece of hardware by using an adapter with a different voltage, but even the same wattage. Slightly different voltages, as other posters have mentioned, may work fine, or they may (in the case of higher voltages) overheat the system and cause damage in the long run, or who knows what else?The OP was right to ask this question, and it still doesn't seem to have been addressed - nor do I know why Apple decided to switch voltages in the first place!Of particular concern is this little piece: 'Adapters that shipped with the MacBook Air (Original), MacBook Air (Late 2008), and MacBook Air (Mid 2009) are not recommended for use with MacBook Air (Late 2010) models. When possible, use your computer's original adapter or a newer adapter.' Watts = Volts. Amps. So when Apple says you can use an adapter with a higher wattage, this would include voltage, right? Apple only refers to.their.
chargers by wattage, so when the article says a higher wattage can be used, I believe they are of course, referring to.their. other chargers.I've never had a problem using a higher wattage adapter. In fact, I'm thinking of ordering a few more cheap 85W spares for my MBP 13', so I have an adapter ready at my desk, couch, etc. Flash content (Youtube,.etc) is a battery drainer!It also seems the 85W does not get near as hot charging my MBP as the 65w does. Hi,I am digging out this thread as I encountered the same question after my original 45W MSA was ripped apart between my desk chair's wheels.I decided to take the risk and buy one I found on a forum, and for the last month or so everything is working fine.
I have no overheating issues, over or undercharges, and no strange behaviour or readings when checking the battery cycles.So I can say that yes, you can use it. The only issue is that the 85W one has the corner-shaped plug while the 45W one was a straight-in. So if you intend to use the usb port, you should expect some minor issues with bulky devices. Apple Footer.This site contains user submitted content, comments and opinions and is for informational purposes only.
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