[Faceplant]

I have a MB and my wife has a new MBP. Brand New, and if I swapped mine with hers, I suspect she would notice. The laptops get used in different parts of the house and the two cords that came with them fit in both just fine, but the output of mine is 16.5v and hers with the larger white thing is 16.5 - 18.5v. Is it safe to go both ways in exchanging them? Can either cord be used with either machine?
My feeble understanding of these things is the rating on them is what they are capable of but not necessarily what they will do constantly.

[mduell]

Yes, you can use either with either machine.
The MBP battery charge rate will probably be pretty slow with the MB adapter.

[Simon]

You can use both chargers with both Macs. No harm will be done.

The only thing to keep in mind is that the MB's 60W charger will only charge a MBP while it's not being used (sleeping or off). It doesn't supply enough power to both run the MBP and charge the battery at the same time. The MBP's 85W charger will not harm the MB.

[scaredpoet]

Originally Posted by Simon 

The only thing to keep in mind is that the MB's 60W charger will only charge a MBP while it's not being used (sleeping or off). It doesn't supply enough power to both run the MBP and charge the battery at the same time. The MBP's 85W charger will not harm the MB.

That being said, I have a feeling the OP's wife would notice a difference if her 85W power supply were swapped out with the OP's 60W one.

[Fusion]

Originally Posted by Simon 

You can use both chargers with both Macs. No harm will be done.

The only thing to keep in mind is that the MB's 60W charger will only charge a MBP while it's not being used (sleeping or off). It doesn't supply enough power to both run the MBP and charge the battery at the same time. The MBP's 85W charger will not harm the MB.

I've heard so many people say this but I've had entirely different results. I use my wife's MB charger on my MBP all the time while I'm using it. I can plug it in when the battery is empty, use it for 2 hours, unplug it and the battery will be full charged. That's constant use with no sleep or off time.

[imitchellg5]

The MacBook adaptor can't charge and power the MacBook at the same time, so you'll have to turn it off to charge, according to Apple. Real world results may vary, but the best advice is to just use your MacBook Pro with a MacBook Pro adaptor, and a MacBook with a MacBook adaptor.

[mduell]

With regard to the MB adapter charging the MBP battery while one, unless they've gone out of their way to disable it, it will probably charge the battery slowly. 60W is a lot more power than the MBP needs unless it's running full tilt (100% CPU, full screen brightness, max USB/FW draw, HDD and optical going, while taxing the GPU, etc), so it should charge. An on but idle MBP burns about 20W, so you've still for 40 for the battery.

[Warbrain]

The 60W power adapter will charge the MacBook Pro while it is in use, it just won't charge it at as quick of a rate as the 85W adapter does. I've had co-workers who have left their charger at home borrow a 60W charger and be just fine while using their MacBook Pro.

[Tomchu]

I've used my girlfriend's MB charger on my MBP, and while it charges it as I use the MBP, the battery measurement systems gets out-of-whack. Don't believe me? :-P Check coconutBattery while the MBP is plugged in via a MB charger. It'll think your total battery capacity is a lot lower than it should be, and it will only charge it to the level shown.

For that reason, I've avoided using her charger, because I don't want to screw with the calibration data the battery has calculated over time.

[Waragainstsleep]

Batteries lose calibration over time anyway. You will do no harm interchanging these adaptors. You may find that charging an MBP from a 60W adaptor won't charge so fast if its running both CPU cores at full pelt, but for browsing or doing less taxing tasks you shouldn't really notice. Might depend which MB/MBP you have to some extent.