View Full Version : MBA w/ 85W Power Adapter long-term?

Apr 7, 2013, 02:03 PM
Hey folks --

Due to a propensity to put my laptop in its bag and leave the charger plugged into the wall, I have a couple of spare power bricks (85W) for my 15" MBP -- the original for home, a spare for the office, and another spare kept at home-away-from-home.

I'm considering switching to a MBA (which uses a 45W power brick), and wondering if I'll have to buy all new chargers. I know you can "safely" charge the MBA from an 85W charger in an emergency, but is that OK for daily use, or can it damage the battery or reduce its life?


Apr 7, 2013, 02:05 PM
It's perfectly fine to charge with a 45w, 60w, or 85w on any MacBook Air.

Apr 7, 2013, 04:11 PM
I've been using an 85w charger, it's fine. 85watts is simply the capacity of the charger, it doesn't force 85watts into the machine. Your MBA will use the power it needs, not more. I keep my 85watt charger at home and the smaller MBA charger in the bag. I actually prefer using the 85watt charger because it barely even gets warm (since the MBA will only use about half it's rated capacity) vs the MBA charger which gets quite toasty when the machine is on and charging.

Apr 7, 2013, 07:01 PM
Is OK. My Air actually knows it's plugged into a 85 watter. Forget what screen. If bad it would flash a big DON'T!

Apr 7, 2013, 07:18 PM
apple themselves say its fine, the laptop will draw what it needs. what they say you cant do is use a lower rated charger, ie 45w on a 15"

Apr 7, 2013, 08:41 PM
You can use a 45w adapter on a 15", it just won't run it *and* charge at the same time, i.e., you can run the laptop, but the battery won't charge.

Apr 7, 2013, 09:26 PM
My understanding, and please correct me if I'm wrong, is that it you use the 85W charger then the computer will only draw what it needs. But the other way around, then charging will take forever. Meaning that if you use a 45W to charge something that needs 85W, then it will take nearly twice as long to charge as it should.

I don't think there is any risk either way, but it will act normally if it takes less than it needs. It will act something like the conversion of DC to AC.

Apr 7, 2013, 10:00 PM
The MBA is fine to charge using the 85W adapter as the MBA wil only draw what it needs.

Now if you use the 45W on the rMBP which requires 85W, the charger is not capable of putting out the required power.

Apr 8, 2013, 08:45 AM
Thanks guys, that helps a lot -- those things are ridiculously expensive!

Apr 8, 2013, 09:06 AM
You're not kidding. I bought the adapters because of it.

Apr 12, 2013, 07:45 AM
You're not kidding. I bought the adapters because of it.

Could you tell me more? What adapters? I need a second supply and have been put off by the cost.


Apr 12, 2013, 08:39 PM
Could you tell me more? What adapters? I need a second supply and have been put off by the cost.


They are just the MagSafe to MagSafe2 adapters. Apple sells them for $10. Amazon has them for the same price with Prime.


Apr 12, 2013, 09:03 PM
Oh, OK. I thought there was an alternative, less expensive power supply.


Brian Y
Apr 13, 2013, 05:41 PM
If you don't need 85w, 45w is cheaper.