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There are 45, 60, and 85 watt power adapters for the MacBook line of portable devices (the Air, the Pro, etc.). Does the 45 watt charger which comes with the MacBook Air work with the 15" MacBook Pro for example?

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You may find this article of value: – user10355 Oct 9 '11 at 5:47

You can use it, but how much actual charging goes on may be minimal. It depends how much power your MBP is drawing (i.e. if you're doing CPU or graphics intensive tasks, you'll draw more power, thus less charging), but I suspect the 45W won't do much more than slow the rate of battery drain. If your MBP is asleep or turned off, it should charge the battery, just slower than the standard charger.

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I've done this a couple times when I was in a pinch. One note - 45W power adapter got EXTREMELY HOT. Much more so than the 85W would during normal usage. So use it sparingly, and definitely not on any sort of regular basis. – chrismanderson Oct 10 '11 at 0:54

Also note that a Pro with a completely discharged battery will not be able to start up off a 45W or 60W adapter at first - I know from first-hand experience that a 60W can charge a 15" Pro's battery enough after a few minutes to allow booting.

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