Use Apple 87W charger with MacBook?

Mike Boreham

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Aug 10, 2006
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I bought an 87W charger as a spare for my 12" MacBook. I didn't get the 29W because I see a 15" MacBook Pro in my future, so thought I would get the 87W now rather than another 29W, believing I could use the 87W with the MacBook, hence more versatile.

But can I use the 87W with my 12" MacBook?

The 29W charger is labelled 14.5V 2A (USB-PD) or 5.4V 2.4A
The 87W charger is labelled 20.V 4.3A (USB-PD) or 9V 3A or 5.2V 2.4A

If I connect the 87W to the MacBook through a Satechi USB-C power meter it charges at 19.2V 1.4A = 26.9W.

With the 29W charger the Satechi shows 15.2V 1.94A = 29.5W

This Apple KB says it recommends using the right charger but also says it is OK to use a higher wattage charger.

"Power adapters for Mac notebooks are available in 29W, 45W, 60W, 61W, 85W, and 87W varieties. You should use the appropriate wattage power adapter for your Mac notebook. You can use a compatible higher wattage adapter without issue, but it won't make your computer charge faster or operate differently. Lower wattage adapters don't provide enough power".

The same KB says to make sure you use the appropriate USB-C cable, which I am...C4Mxxxxxx for 29W.

This Apple KB says:

"Your Mac will charge from USB-C power adapters not manufactured by Apple if they adhere to the USB Power Delivery specification".

Since both the Apple 29W and 87W USB-C chargers are both USB-PD I should be OK, I think.

If the 87W charged at 15V like the 29W does I would have no doubts....I just wasn't expecting the 87W to charge at a higher voltage....even though the wattage is the same.

Thanks for any comment.
 
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masotime

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I think it should be safe. It seems the MacBook Pro power adapters were mainly designed to run at a higher voltage, i.e. 20V. It's good that the 12" MacBook negotiates at 20V instead of 9V though..... I suspect that it is not designed to accept a current larger than 2A.
 
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Mike Boreham

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I think it should be safe. It seems the MacBook Pro power adapters were mainly designed to run at a higher voltage, i.e. 20V. It's good that the 12" MacBook negotiates at 20V instead of 9V though..... I suspect that it is not designed to accept a current larger than 2A.
Thanks. Yes It seems to negotiate at the same 30W if connecting USB-PD, so 2A with 15V or 1.5A with 20V.

I have read that (especially nowadays with all the potential for confusion about USB-C) Apple devices have built-in protection against such issues. This is supported by my experience with a non-Apple USB-C (PD) charger which won't charge the MacBook at all.
 
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ascender

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Dec 8, 2005
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Yes, so long as you're using an official Apple usb-c charger and cable, you're good to use more powerful or less powerful chargers on different products.
 
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Mike Boreham

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I use the 61w charger with my 2016 MB, no problem.

Thanks very reassuring...I believe the 61W has the same output voltage specs as the 87W.
[doublepost=1491403707][/doublepost]
Yes, so long as you're using an official Apple usb-c charger and cable, you're good to use more powerful or less powerful chargers on different products.
Thanks. Apple have confirmed to me on a support app chat that it is OK. I wouldn't have had any doubts if it wasn't for the higher voltage with the 87W.
 
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BeatCrazy

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Jul 20, 2011
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[doublepost=1491403707][/doublepost]

Thanks. Apple have confirmed to me on a support app chat that it is OK. I wouldn't have had any doubts if it wasn't for the higher voltage with the 87W.
Well that is good, but for some reason I trust the guy in the video more than Apple chat support ;)

Actually Apple is really good at making sure their chargers are compatible across models. I occasionally use my iPad 12w charger to charge my MacBook!
 

m0dest

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Apr 16, 2010
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Apple's 61W and 87W chargers violate the USB-PD spec a little. They don't offer a 15V mode; only 5V, 9V, and 20V. This isn't a huge problem, but 2 side effects:
  • The 12.9" iPad Pro only supports 5V, 9V, and 15V charging and limits itself to 2A. Since 15V isn't supported on Apple's 61W/87W chargers, it's stuck using 9V at 2A (18W) instead of 15V at 2A (30W). It charges more slowly with the 61W/87W chargers than on the 29W charger.
  • The 12" MacBook supports 5V, 9V, 15V, and 20V charging. Since 15V isn't supported on Apple's 61W/87W chargers, it uses 20V instead of 15V. This isn't an issue, and you should get the same power delivery.
 

Mike Boreham

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Original poster
Aug 10, 2006
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Apple's 61W and 87W chargers violate the USB-PD spec a little. They don't offer a 15V mode; only 5V, 9V, and 20V. This isn't a huge problem, but 2 side effects:
  • The 12.9" iPad Pro only supports 5V, 9V, and 15V charging and limits itself to 2A. Since 15V isn't supported on Apple's 61W/87W chargers, it's stuck using 9V at 2A (18W) instead of 15V at 2A (30W). It charges more slowly with the 61W/87W chargers than on the 29W charger.
  • The 12" MacBook supports 5V, 9V, 15V, and 20V charging. Since 15V isn't supported on Apple's 61W/87W chargers, it uses 20V instead of 15V. This isn't an issue, and you should get the same power delivery.
Thanks very much for clear and helpful summary.
 

tdream

macrumors 65816
Jan 15, 2009
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Sorry to drag up an old post, but I'm considering buying the 2017 macbook because it's to only fanless macbook left.

How long does it take to charge from 0 to 100? With the standard charger or the 20v charger.
 

MrUNIMOG

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Sep 23, 2014
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Sorry to drag up an old post, but I'm considering buying the 2017 macbook because it's to only fanless macbook left.

How long does it take to charge from 0 to 100? With the standard charger or the 20v charger.
I'd wait for the next MacBook, since the current one is already 2 years old. I have a feeling the next one might be the first ARM Mac.

If you can't wait maybe take a look at the 2018 MBA. While it does have a fan, it's using a semi-passive thermal design.
You'll probably never have the fan turn on in everyday usage, maybe someone who owns it can confirm.
 

537635

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Mar 7, 2009
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Slovenia, EU
Apple's 61W and 87W chargers violate the USB-PD spec a little. They don't offer a 15V mode; only 5V, 9V, and 20V. This isn't a huge problem, but 2 side effects:
  • The 12.9" iPad Pro only supports 5V, 9V, and 15V charging and limits itself to 2A. Since 15V isn't supported on Apple's 61W/87W chargers, it's stuck using 9V at 2A (18W) instead of 15V at 2A (30W). It charges more slowly with the 61W/87W chargers than on the 29W charger.
  • The 12" MacBook supports 5V, 9V, 15V, and 20V charging. Since 15V isn't supported on Apple's 61W/87W chargers, it uses 20V instead of 15V. This isn't an issue, and you should get the same power delivery.
Great post!

So you would actually charge an iPad Pro faster if you connected it to a Macbook Pro's USB-C port than to its 87W charger?
 

chrfr

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Jul 11, 2009
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Apple's 61W and 87W chargers violate the USB-PD spec a little. They don't offer a 15V mode; only 5V, 9V, and 20V. This isn't a huge problem, but 2 side effects:
  • The 12.9" iPad Pro only supports 5V, 9V, and 15V charging and limits itself to 2A. Since 15V isn't supported on Apple's 61W/87W chargers, it's stuck using 9V at 2A (18W) instead of 15V at 2A (30W). It charges more slowly with the 61W/87W chargers than on the 29W charger.
  • The 12" MacBook supports 5V, 9V, 15V, and 20V charging. Since 15V isn't supported on Apple's 61W/87W chargers, it uses 20V instead of 15V. This isn't an issue, and you should get the same power delivery.
The newer 61W charger, model A1947, which began shipping with 2018 13" MacBook Pros, supports more PD options, including 15V@3A. The older version, model A1718, does not. The full range the A1947 supports is as follows: 20.3V@3A, 15V@3A, 9V@3A, 5.2V@3A. The older A1718 model only offers 20.3V@3A, 9V@3A, or 5.2V@ 2.4A.
There has not been a corresponding change to the 87W adapter.
 
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corduroygt

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May 29, 2005
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If you can't wait maybe take a look at the 2018 MBA. While it does have a fan, it's using a semi-passive thermal design.
You'll probably never have the fan turn on in everyday usage, maybe someone who owns it can confirm.
When using it at a laptop, it turns on rarely. When using with an external monitor, it's almost on all the time.
 
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