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Power MBP from MB's smaller AC adapter?
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Addicted to MacNN
Join Date: Jan 2003
Location: ~/
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While I understand that the smaller (65W) MagSafe AC power adapter for the MacBooks will physically connect to a MacBook Pro but may not have enough juice to both power and charge the MPB battery at the same time.
But, do you think that the smaller power supply could adequately at least power the machine (and charge when the machine is off/sleeping), or will the MBPro just burn out the smaller MB power brick.
I'm trying to save some weight, even a little, in my travel bag.
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Senior User
Join Date: Nov 2000
Location: New Orleans, LA
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the power adapter for the Macbook wil power and charge the Macbook Pro, just at a slower pace.
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Mac Enthusiast
Join Date: Apr 2001
Location: Ottawa, ON, Canada
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Are you quite sure about this ?
If so, it would solve an issue that a lot of people have - the 85w power supply will trip the breaker of airlines' in-seat power systems. I think I'll give it a try on my trip round APAC next week and report back....
Ben.
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Mac Enthusiast
Join Date: Apr 2001
Location: Ottawa, ON, Canada
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Well I gave it a try...
Firstly of note, this is my own experience, YMMV.
The 85W MBP power adaptor supplies:
16.5V DC @ 3.6A *and*
18.5V DC @ 4.6A
The 60W Macbook power adaptor supplies
16.5V DC @ 3.6A only.
So you might figure that the 16.5V supply runs the system, and the additional 18.5V supply is used for charging....
If the battery in the MacBook Pro is above a certain level, the 60W adaptor will cause the system to recognise AC power connected, no charging. The magsafe LED will be green, even though the battery will not be fully charged. **this works in the aircraft without tripping the breaker**
If the battery is below a certain level, then the MBP tries to charge from the Macbook 60W adaptor, and bad things happen. The power supply crackles and hums, and heats up to over 100 degrees farenheit (goodness knows when any kind of thermal protection kicks in)...
I'd guess that the "certain level" will be a mAh charge that the power supply is capable of providing. i.e. it's probably 60/85 * 100 = 70% of the MBP capacity.
I'm assuming therefore, it is reasonably safe to use a macbook charger on a plane with a macbook pro, as long as your battery is charged to over 70% before you try to use the adaptor. I don't recommend this, and I'm still unhappy with the in-air solutions for the MacBook Pro. I now carry around three batteries.
Ben
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