2
Score
mister790
2.1k
Asked
Definitive answer on using 60w or 85w power adapter with 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 from the and that the Macbook Air can't sit flat on a surface if you use them -- I'm just curious if it's safe for the electronics to use them.)
Thanks!
6
Score
bac
5.1k
Answered
Accepted Answer
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.
The charger is a dual-voltage charger. It uses 16.5V for normal operations and switches to 18.5V for intensive tasks.
Gabe,
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?
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!
2
Score
rdklinc
15.3k
Answered
I can't offer a technical explanation, but I have a couple 85W magsafes on my workbench that I use with all MacBooks I encounter, the logic being that they are powerful enough to run any MacBook I might work on. I've never had a problem using them on Airs. My impression is that MacBooks only use the amount of available power they need, and that the AC adapter does not shove power "down its throat", so to speak.