Will my MacBook Pro charging cord safely work to charge my MacBook Air -- and vice versa?

Hi T,

The MBA uses a 45watt charger.

The MBP uses an 85watt charger.

I've never tried it, but I sure would never try it on my machine or any machine anyone cared about. 45 will not charge the 85 properly, and 85 could possibly (probably?) cause damage to the MBA.

You can safely charge the MBA with the charger from the MBP, the MBA charger will not supply enough power to charge the MBP.

The MBP charger will not damage the MBA, the MBA will draw what it needs (45w) so the MBP charger will not have to work very hard.

Tuffy Nicolas wrote:

Hmmmm...but I just finished talking to a "genius" at an Apple store (before I saw your answer) and he told me that the Air's plug would not charge the Pro (as you describe), BUT that the Pro's plug would indeed safely charge the Air, with no risk of damage.

Are you basing your advice on general wisdom about how electronics works, or on specific knowledge concerning the way Pros and Airs interact with power cords of different types?

As you said, "general wisdom" (with more emphasis on the "general" than the "wisdom" 😉). I do not dispute what he said, but if I were in the Apple Store, I'd have him show me on their machines before I'd even think about trying it on mine. And I have to say, from what I know about charging and over charging lithium batts, that is probably still not something I'd try on my equipment. Of course ymmv. I hope you'll post back with results.

Hi tjk

Power drawn from a supply is governed by the load (MBA) not the charger, thus: a 45w load (MBA) will draw 45w, the MBA charger can deliver 45w so all is well, the MBP charger can supply 85w so all is also well (only 55% of it's capacity is being used)

Conversely the MBP will draw 85w and will be just fine with it's own charger (which can supply 85w) but will only be able to draw 45w from an MBA charger so will not charge.

I'm a certified low & high voltage tech, and I have a heap of Mac portables.

To the OP

Go ahead with your plan, no damage will result.

Csound1 wrote:

Hi tjk

Power drawn from a supply is governed by the load (MBA) not the charger, thus: a 45w load (MBA) will draw 45w, the MBA charger can deliver 45w so all is well, the MBP charger can supply 85w so all is also well (only 55% of it's capacity is being used)

Conversely the MBP will draw 85w and will be just fine with it's own charger (which can supply 85w) but will only be able to draw 45w from an MBA charger so will not charge.

I'm a certified low & high voltage tech, and I have a heap of Mac portables.

To the OP

Go ahead with your plan, no damage will result.

Thanks for the explanation C, I appreciate it. 😉

You're welcome

That is also correct, the MBA supply will deliver approximately half of the energy the MBP needs to run & charge, this means that while it's in use it will discharge until either (a) flat, or (b) switched off. I would use the MBP charger for both machines (if you are intending to carry only one charger with you)

And thanks for the points.

I was wondering about this myself. I have an 11" Air and a MacBook Pro. I keep the Air charger in my backpack, but occionally I take the MB Pro with me and I have wondered if it would charge (or maintain the power for my MB Pro).

It's rare I run the battery down, but I feel the need to have a spare charger with me.

But Apple makes the Apple MagSafe Airline Adapter

"With the MagSafe Airline Adapter, you'll never again worry about losing power while traveling. Just plug it into your airline seat power port and keep your MacBook, MacBook Pro, or MacBook Air computer powered up for the entire flight." and

"Using the MagSafe Airline Adapter provides power for your computer but does not charge the battery."

But they have no distinction between the MB. I don't believe this is supposed to charge your MB, just maintain it. I have seen some people say it it doesn't keep it fully charged and have had it go dead.

As I said, I just hoped it would maintain the charge for me (or perhaps charge overnight with the MB Pro off).

I have read that different adaptors have slightly different output voltages.

Plus, Apple makes the 27 inch displace with MagSafe charger and it's supposed to charge all models, right?

That said: There desn't seem to be a distinction when purchasing replacement adaptors.

I also noticed my MB Pro from this year didn't have the right-angle MagSafe connector, I thought

On the other hand:

I see that on http://support.apple.com/kb/HT2346 and this is kind of odd in my opinion.

Apple says:

Note: 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

This one really surprised me that Apple says there are differences between MacBook Air model chargers!?! Or are they just saying the connectors are more flimsy or something (maybe they recalled those). This seems really strange, especially when you consider how small (and gray) they make the print on these. How can you tell the difference if they aren't labeled well.

Gary

You can use the MBP charger with the Air without issue, using the MBA charger with the Pro will work but the charger is incapable of charging the MBP while it is running (not enough power available) it will run, and it will charge it but only if you switch off.

Take the MBP charger, that way you can charge either machine.

Those older (<= 2008) power bricks came with a MagSafe T-connector, in contrast to nowaday's L-connectors. Never having ripped one open, can't imagine what overwhelming difference may lay inside, but Apple even had to put out a firmware patch when the L-connectors came out so the older Macs could use them. But as even our Certified Electrician has pointed out, since both have L's, you'll be fine using the big'un on the little'un.

Woe befall you should you drink the Retina koolaid; those things have a different and incompatible MagSafe 2 power brick that returns to the T-connector formfactor (and requires an adapter to use a regular powerbrick, $20)

My MacBook Pro 13 inch mid-2012 still came with an MagSafe (1) but went back to the T-connector.

Gary

But the MBP charger is a lot heftier and 9 out of 10 times I don't need a charger. That's why I started looking for an answer to this. I just want to carry the smaller charger.

I'd prefer not to carry a charger at all, but sometimes things happen and since I can't carry a spare battery, I need a charger.

Gary

garylapointe wrote:

But the MBP charger is a lot heftier and 9 out of 10 times I don't need a charger. That's why I started looking for an answer to this. I just want to carry the smaller charger.

You can use either charger with either Mac. You just won't be able to charge the Pro from the Air charger while using it.

Carry what you like, you now know what the result will be.