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PostPosted: Wed Dec 09, 2015 2:52 pm 
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I have a 15" early 2008 Macbook pro 4,1 with 85 watt magsafe adapter. Can I temporarily use that 85 watt adapter with a 13" early 2011 macbook pro 8,1 that normally uses a 60 watt magsafe adapter. I've read it is fine.

Can I get confirmation it's OK?


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PostPosted: Wed Dec 09, 2015 4:03 pm 
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I haven't tried it, but also read it was fine to do.


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PostPosted: Wed Dec 09, 2015 5:31 pm 
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You can use the higher wattage adapters for lower wattage computers, but lower wattage adapters won't work on computers that require higher wattages. The wattage on the adapter describes how many watts the adapter is capable of supplying. The wattage of the computer is the maximum it will attempt to draw, even if it usually draws less. The 13" models never draw 85 watts, so they can use either adapter. The 15" model may draw up to 85 watts, so it cannot use lower wattage adapters.

In other words:
85W adapters (for 15") work with 15" and 13" models.
Lower W adapters work only with 13" models.

When I buy replacement adapters I always get the higher wattage models because they're the same price and work with everything (that they'll physically plug in to).

- Anonymous


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PostPosted: Wed Dec 09, 2015 7:34 pm 
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Thanks guys!


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PostPosted: Wed Dec 09, 2015 9:26 pm 
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Anon, please correct me if I'm wrong, but in a pinch, can a lower wattage one not be used on higher wattage Laptop, but just slower charging???


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PostPosted: Wed Dec 09, 2015 10:46 pm 
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I haven't tried, but my guess is that if it charges it'll charge very slowly, and it might not even do that unless it's asleep, or at all. The computer can talk to the charger (or more specifically a very, very tiny chip in the magsafe connector itself), but I don't know if it will reject power adapters that announce themselves to the computer as supplying fewer watts than the computer expects to be able to draw. I just haven't tried. I am however entirely comfortable trying: it won't hurt anything if you're using an Apple-built adapter in good condition.

- Anonymous


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PostPosted: Thu Dec 10, 2015 3:40 am 
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If you shut down the computer, a lower wattage supply will charge the battery, however if you then power on the system with the adapter connected the battery will slowly drain. That's based on my experience with a user with a 17" MBP who was issued a 60w adapter after their adapter's cord got mangled. Thankfully I wasn't the guy who issued it.


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PostPosted: Thu Dec 10, 2015 7:12 pm 
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Thanks MB & Anon. :)


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PostPosted: Thu Dec 10, 2015 8:44 pm 
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Been using it most of the day with no issues. Thanks again!!


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