CHARGING

wowee

macrumors member
Original poster
May 23, 2015
69
13
Sorry if this has been asked before - can you charge the new Macbook by connecting it to the USB on a MACBOOK PRO or AIR?

Thanks!
 

Theophil1971

macrumors 6502
Mar 20, 2015
388
168
USA
Hmmm... I doubt that the USB on another computer supplies sufficient wattage to efficiently charge the rMB. If it charges it at all, I'd think it would be veeeerrry slow and not really worth it.
 

palmwangja

macrumors regular
Apr 12, 2015
126
16
You need at least 2A, but I don't think PCs usually don't push juice that hard.
 

soupcan

macrumors 6502a
Nov 21, 2014
725
2,926
Netherlands
Well, according to Apple the MacBook's power brick delivers 29 Watt. Now, according to this Apple support page, a standard USB 3 type A plug can deliver 900 mA at 5V, or 1100 mA at 5V for charging iDevices. A quick calculation answers your question: at 900 mA and 5V you can deliver up to 4.5W, and in the overdrive function you can do 1100 mA*5V=5.5W. Both of those are well under the 29W the MacBook needs, so no, any current Macs can charge a MacBook.

USB-C (normally) can't provide those Amps either, but Apple build in a special version of it with the USB Power Delivery standard, which can provide up to 100W trough a USB-C cable. Apple is using that in their charger.
 
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keviig

macrumors 6502
Jun 7, 2012
498
225
While it may not be enough to charge while using it, it can delay the discharge or you can charge it over night. The rMB has a 39.7 Wh battery. At 5,5W it will take you just over 7 hours for a full charge.

I have a 12v car phone charger that delivers 1A or 5W and it does charge the rMB, just very slowly. At low screen brightness its enough to sustain the charge it had when i started.
 

soupcan

macrumors 6502a
Nov 21, 2014
725
2,926
Netherlands
While it may not be enough to charge while using it, it can delay the discharge or you can charge it over night. The rMB has a 39.7 Wh battery. At 5,5W it will take you just over 7 hours for a full charge.

I have a 12v car phone charger that delivers 1A or 5W and it does charge the rMB, just very slowly. At low screen brightness its enough to sustain the charge it had when i started.
It'll probably shut down the USB port on the Mac the MacBook is charging off of due to an overload and OS X protecting you from a fried USB port/logic board.
 

keviig

macrumors 6502
Jun 7, 2012
498
225
It'll probably shut down the USB port on the Mac the MacBook is charging off of due to an overload and OS X protecting you from a fried USB port/logic board.
Why would it shut down the USB port? The USB port will only provide as much power as it's designed to.
 

soupcan

macrumors 6502a
Nov 21, 2014
725
2,926
Netherlands
Why would it shut down the USB port? The USB port will only provide as much power as it's designed to.
Not if the recipient device wants more. Try hooking up a wired keyboard to any Mac with a wired mouse on one end and an external HDD on the other end. Within 5 minutes OS X disables the USB port the keyboard is connected to.
 

keviig

macrumors 6502
Jun 7, 2012
498
225
Not if the recipient device wants more. Try hooking up a wired keyboard to any Mac with a wired mouse on one end and an external HDD on the other end. Within 5 minutes OS X disables the USB port the keyboard is connected to.
Different to how a charger works then. I will give it a try when i get home!
 

bibyfok

macrumors 6502
Jun 14, 2012
335
6
France
It was not The Verge but 9to5mac:

You can also charge the 12-inch MacBook… from another 12-inch MacBook. Connect the included USB-C Charge Cable ($29) from one 12-inch MacBook to another, and whichever Mac was connected first will charge the Mac you connect next.​
 

fatefulwhisper

macrumors regular
Jul 24, 2008
171
21
Sorry if this has been asked before - can you charge the new Macbook by connecting it to the USB on a MACBOOK PRO or AIR?

Thanks!
Yes, you can. I tried to plug in a USB-C to USB-A cable from rMB to MBAir and it was charging the rMB, but very slowly.
 
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wowee

macrumors member
Original poster
May 23, 2015
69
13
Thanks so much! Good to know it's "possible" - was just curious. I had heard charging from another rMB was no probs but was curious about from my macbook pro as I leave my rMB next to it at night.

Another question - is it possible to use the rMB as an external monitor next to my Macbook Pro?
 

Queen6

macrumors G3
Thanks so much! Good to know it's "possible" - was just curious. I had heard charging from another rMB was no probs but was curious about from my macbook pro as I leave my rMB next to it at night.

Another question - is it possible to use the rMB as an external monitor next to my Macbook Pro?
rMBP to rMB, just need the cable, however is very slow, As for the display maybe this can, equally not natively.

http://www.inateck.com/hb4009-4-port-usb-3-0-hub-km-switch-transfer-files-from-pc-to-pc/

Q-6
 
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