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I have a MacBook pro that is about 4 years and its power adaptor broke it says on it 85W. Do you think if I get the new 60W ones it will work? Will it affect my computer?

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up vote 4 down vote accepted

The 60W should be OK on the MBPro. The Output on it is 16.5V-3.65A.

The 85W MPBro charger lists two outputs:

18.5V-4.6A and 16.5V-6.5A

Not sure why or how it's rated for two outputs; maybe an EE could explain..

I believe the caveat to using a 60W charger on a MBPro is that your battery may not charge while you are actually using the laptop. Should charge while it's off or asleep..

Might be careful the other way around though ( 85W charger on a Macbook ) ... though I have to believe Apple would have stickers on the chargers and KB's explaining that it shouldn't be done if there were a serious issue..

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2  
You can use either charger with either. The way the system works is with an 85W adapter, the adapter will bump the voltage if you're trying to charge + max CPU on the system at the same time. What this means with a 60W adapter is if you try to charge the battery and use performance intensive-tasks, it will stop charging until the CPU usage drops back down. Opposite, the 60W MacBooks will simply not request the bumped-up voltage, so the 85W adapter will only ever feed it 60W. – Darth Android Oct 18 '10 at 19:56
    
Thanks, never quite knew how the dual voltage worked exactly... – CaseyIT Oct 18 '10 at 20:48
    
Thanks. I got one and it seems to work fine :) – Tam Oct 19 '10 at 3:15
up vote 1 down vote

At best it will charge slower, at worse it won't charge at all. I wouldn't mess around with different wattage chargers.

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