Can I use 85W adapter w/ MB?

[ncook06]

Well, I'm returning my MBP. I have an extra 85W power adapter, but the Macbook only uses 60W. It seems like it would be very dangerous for me to use it.

What do you experts think?

[mkrishnan]

In the past, this has been fine. All the voltages of iBook/PB adaptors work on the iBook 12", even though it only needs the smallest one. (not vice versa -- a 17" PB cannot run itself and charge its battery off an iBook adaptor).

When you look at power adaptors, the VOLTAGE is very, very, very critical. Because the way they work, they provide a constant voltage (e.g. 24V) and the current adjusts based on power requirements (since the power output is a product of the two). So if a power supply has the same voltage, but it produces twice as much maximum power, then it just runs at a lower current when it's hooked up to a device that doesn't need the power (this is called "current draw").

In other words, you should almost certainly be fine. Apple would have made the plugs different if they weren't compatible, because you know people in business settings or at the Apple store would accidentally plug in the wrong adaptor. But they didn't, because it isn't an issue. :)

[ncook06]

One of my friends just got a Macbook. It seems that the 85W can charge either.

[tristan]

I just read a review in MacWorld that says that either adapter will work with either laptop.

[ncook06]

I just read a review in MacWorld that says that either adapter will work with either laptop.

Thanks so much. Answers all of my questions.