Is it OK to use 17″ Macbook Pro AC adapter on a 13″ Macbook Pro

ac-adapterpower supply

17" Magsafe Adapter:

Input: 100-240V – 1.5A 50-60Hz

Output: 16.5-18.5V – – – 4.6A Max

13" Magsafe Adapter

Input: 100-240V – 1.5A 50-60Hz

Output: 16.5V – – – 3.65A

The Answer:

I am looking for a yes/no answer here, but most importantly, I want to know why it's (not) ok.

Best Answer

As the voltage is the same, you should have absolutely no problem using it. Note that you should only use a power adapter that is spec'd higher.

So this is fine: 17" adapter on 13" model.
This is not: 13" adapter on 17" model.

See also this Apple FAQ:

Although you should always use the proper wattage adapter for your Apple portable, you can use an adapter of a higher wattage without issue.

For instance If you have a MacBook (13-inch Late 2009) that normally uses a 60W adapter, you can also use an 85W adapter with that computer. You would not use a 45W adapter with that computer; it would not provide enough power for that MacBook. Using an adapter of higher wattage than the adapter that came with the computer will not cause the computer to charge more quickly or otherwise operate any differently than using the adapter that came with the computer.

I think there's not much to add to this. From my own experience however it seems that you can still use a lower wattage adapter and your Macbook will work. I sometimes used charged my 15" on a smaller 13" adapter and didn't run into any notable issues, but who knows. It will probably not charge that fast. The fact that you have a battery also means that the Macbook won't just power down. For the sake of not voiding the warranty, you should just follow those guidelines.

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