iPad Pro 87W USB-C charger doesn't charge 12.9" iPad Pro @ 29W

Discussion in 'iPad' started by masotime, Nov 16, 2016.

  1. masotime, Nov 16, 2016
    Last edited: Nov 16, 2016

    masotime macrumors 68000

    masotime

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    #1
    Mostly a PSA (public service announcement) - this probably also applies to the 61W USB-C charger as well.

    I decided to spin off a new thread for better visibility - the original thread of discussion was http://forums.macrumors.com/threads/12w-charger-for-ipad-pro-9-7.2012895/#post-23877702.

    With the new Touchbar MacBook Pros now being widely available, I was able to purchase the 87W USB-C Charger to test it against the 12.9" iPad Pro to see if there was any chance it could also fast charge.

    The charger had the following output specifications:

    IMG_0817.JPG

    As can be seen, there is no apparent support for the 14.5V / 2A charging needed to achieve 29W speeds on the 12.9" iPad Pro.

    To confirm this, I ran two tests against the 29W charger I have, using the official USB-C to Lightning cable from Apple. My testing methodology was to drain the iPad Pro with GFX Bench Metal's Battery test, running it several times. In the 0% case, I effectively drained the iPad Pro until it shut itself off. These are the results:

    87W USB-C Charger
    • 37% to 54% in 31 mins, 17% in 31 mins or 0.55% / min
    • 0% to 38% in 60 mins, or 0.63% / min
    29W USB-C Charger
    • 36% to 52% in 18 mins, 16% in 18min or 0.89% / min
    • 0% to 56% in 60 mins, or 0.93% / min
    Charging speeds are not linear, explaining the differences in the calculated averages for the same charger.

    However, it is clear that the 87W charger does not charge at 29W. I'd need to test against a 12W Charger to confirm if the 87W USB-C charger is running at 5.2V / 2.4A (~12W), but otherwise it looks like if you own one of the newer MacBook Pros you can't rely on a do-it-all charger for maximum charging speeds. Pretty disappointing IMO.
     
  2. Brookzy macrumors 68040

    Brookzy

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    #2
    Thank you for this! I was supposing similar things in this thread: http://forums.macrumors.com/threads/what-power-will-2016-mbp-draw-from-29w-usb-c-charger.2011017/ where I got the charging specs from the regulatory information (which you have verified in your image!).

    I'm still trying to answer the reverse question (in my linked thread) about what happens if you plug a 29W charger into a MacBook Pro. Given what you've found above do you think you could shed any light on this? Will a 29W charger plugged into a MacBook Pro default to 29W mode or 12W mode?
     
  3. masotime thread starter macrumors 68000

    masotime

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    #3
    I did a quick google: https://www.macstories.net/ios/testing-apples-29w-usb-c-power-adapter-and-ipad-pro-fast-charging/

    It doesn't look good actually. I am not so sure the new MacBook Pros can negotiate 14.5V when it's marked as ~20V on the 87W adapter. It's more likely to negotiate at the much lower 5V :confused:. The only way to know for sure is to test it at the store . Possibly install coconut Battery to see what the actual output is.

    It's pretty annoying that Apple didn't just go with the same 14.5V across all devices, but I suppose that would mean a 6A current which may not be safe to use...
     
  4. Brookzy macrumors 68040

    Brookzy

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    #4
    That's what I'm thinking, too - that the MacBook Pro will go at a useless 5V 2.4A for 12W. Maybe enough to trickle charge overnight (which is all I need) as at full efficiency would take 4.2 hours for a 50 watt hour MBP battery?

    Definitely. I was hoping I could bring one brick around with me for charging iPhone, iPad and MacBook but with the MBP chargers not supporting iPad fast charge this isn't an option.

    True. I believe the USB-C spec is maximum 20V 5A for 100W? (Though Apple exceeds that voltage limit by 0.2V. Maybe they're purposely stretching the spec into the tolerance zone.)

    Weirdly the Belkin USB-C 3.1 Gen 2 cable Apple recommends for use with the MBPs is listed as only supporting 3A which is less than the 4.3A required.

    This spec is a mess.
     
  5. masotime thread starter macrumors 68000

    masotime

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    #5
    I am curious about the 9V / 3A specification though. Will that be the "fast charging speed" introduced to other iOS devices like the iPhone in the future...? Otherwise I'm not aware of any other Apple device that runs at that specification.
     
  6. Brookzy macrumors 68040

    Brookzy

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    #6
    I've just done some digging online and have figured out the answer!

    It does not appear that 9V 3A is a hint at future fast charging for iOS devices. I found a Benson Leung article where he states the latest USB PD specification rules mandate the following permissible voltages:
    • 5V
    • 9V
    • 12V (optional)
    • 15V
    • 20V
    (N.B. clearly Apple is utilising the permissible tolerances to use, for example, 20.2V.)

    The key here is the specification rule that "larger wattage power sources must support all voltage levels below their maximum up to 3A". So Apple had to support 5V and 9V to meet the spec. (12V is now optional hence no support for that).

    Interestingly, the reason for this rule's existence is that it should allow any higher wattage USB-C power adapter to perform at least equally to a lower wattage one. But, as is the whole point of this thread, this is not the case - the 87W USB-C power adapter does not perform anywhere near as well as the 29W charger for charging iPad Pro.

    It seems to me that Apple has been naughty here. The 12" MacBook and 12.9" iPad Pro do not support the USB-C Power Delivery specification and consequently has caused this dilemma of "bigger is better" not holding.

    But then again, the 29W fast charge mode is 14.5V 2A - is that not close enough to 15V for it to be conforming to the 15V option in the spec? I assume not, even though 20.2V is close enough to 20V to count as conforming to the spec. It seems bizarre, then, that all this fuss is over 0.3V!

    Apple has also created a headache for third parties like Anker whose USB-C chargers are spec-compliant but have compatibility issues with the MacBook when used with the Multiport adapters for instance - when the root cause is Apple's non-adherence to the spec!

    (That post went longer than expected. Who'd have thought voltages could be so interesting! :p )
     
  7. Brookzy macrumors 68040

    Brookzy

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    #7
    @masotime - A follow up to the original point of your thread after doing some more research. If I have misunderstood anything I've read please do correct me.

    It appears the reason the 61W and 87W do not support 14.5V 2A is that it would violate the specification.

    Long story short, the 29W power adapter was designed before the USB Power Delivery specification was published, and once it was published 14.5V 2A was not included.

    However because Apple is well regarded in the consortium they grandfathered it into the specification.

    So, the 29W power adapter is compliant by a grandfathering technicality but including 14.5V 2A on the new chargers would make them noncompliant.

    One might wonder why Apple cares about being compliant (they usually are happy to do things their own way) however after the cockup that led to the USB-C cable recall, and after their shortsightedness in originally making the USB-C Charge Cable only 3A* (this was silently refreshed over the summer to an excellent quality 5A cable) Apple has apparently switched attitude to complying precisely with the rules. This is according to USB-C cable tester Nathan K who said something along the lines of "Apple are being brutally adherent to the letter of the specification".

    Hence this new attitude places adherence to the spec as more important than the ability for one charger to do everything.

    *Again, this is probably down to their original engineering philosophy of violating the spec; they were planning on using noncompliant high voltages to counter the 3A limit. Then they had their change of heart.
     
  8. masotime thread starter macrumors 68000

    masotime

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    #8
    Thanks for the update @Brookzy, excellent work on the research.

    If what you say is correct, then I'm hoping that the next generation of iPad Pros will be spec compliant, then we can reduce ourselves to one single charger to charge everything, which would be really convenient.
     
  9. profets macrumors 68040

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    Mar 18, 2009
    #9
    Good thread, thanks masotime and Brookzy for sharing this info.

    As dull as this topic probably is to most people, I find it fascinating for some reason.

    I'm curious now to see if the next generation of iPads will follow the spec or continue to use the 14.5V 2A (I'm hoping its the former).
     
  10. Brookzy macrumors 68040

    Brookzy

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    #10
    It is strangely interesting isn't it?!

    I hope it changes too, but this would require the retina MacBook to migrate to conformity also.

    Another interesting morsel is that the reason no MFI USB-C to Lightning cables exist is because the Apple ones are rammed full of complex circuitry to cope with the 29W adapter's noncompliance whilst still maintaining safety by declining to draw power from other (non-Apple) noncompliant chargers. In other words, they can recognise the difference between 'compliant', 'Apple non-compliant', and 'bad/third party non-compliant'. I'm not sure if these cables are smart enough to be future-proofed for a move to compliance, or if it will require another silent refresh of the cables à la the USB-C Charge Cable.

    Annnnd that's enough tragic geekiness for one day... ;)
     
  11. xraydoc macrumors demi-god

    xraydoc

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    #11
    This is a little bit of a bummer. I have the new 13" MBP with the 61w charger. I was hoping to be able to travel with just one charger (the 61w one) plus a USB-C to USB-C cable and a USB-C to Lightning cable, and rapidly charge both my MBP and my 12.9" iPad Pro off the same charger. Not that the 29w charger is too big to bring with, but just in terms of keeping things simple.

    I wonder if the MBP's USB-C ports will support rapid charging of a 12.9" iPad Pro...?
     
  12. dannys1 macrumors 68020

    dannys1

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    UK
    #12
    They do exist, I bought one from BC Master on Amazon.

    [​IMG]
     
  13. Brookzy macrumors 68040

    Brookzy

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    #13
    Considering they can't even capitalise the "C" on their own packaging I wouldn't trust them. :rolleyes:

    Straight from the horse's mouth:
    Screen Shot 2016-11-27 at 20.02.19.png
     
  14. dannys1, Nov 27, 2016
    Last edited: Nov 27, 2016

    dannys1 macrumors 68020

    dannys1

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    #14
    That "Type-c" bit isn't on the actual box.

    [​IMG]

    [​IMG]

    They could be using the MFI logo illegally, they are from China of course, but the connector also has the gold pins of the official one and it's usually pretty easy to spot a non Apple connector

    [​IMG]

    Interestingly it's one of few USB-C cables i've bought recently that uses a full wrap around USB-C plug and not a crimped connector which is the supposed USB-C standard. Even Belkin are incorrectly using crimped connectors, the only ones i've been able to find that are made properly are these and Apples - maybe this is out the back of the Apple factory...that I wouldn't be surprised about at all!
     
  15. Brookzy macrumors 68040

    Brookzy

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    #15
    It has a white faceplate insert on the Lightning end. An Apple cable should have a grey face plate. It's fake.
     
  16. dannys1 macrumors 68020

    dannys1

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    #16
    Ah good spot, they're using the MFI logo illegally then.

    Nevermind, I tested it and it works, so it'll be useful for the one time a year I connect my iOS devices to a computer to backup before restoring to the new one.
     
  17. JTravers macrumors 6502a

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    #17
    Does it fast charge with an Apple 29W USB-C adapter?
     
  18. bradbomb macrumors regular

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    Los Angeles, CA
    #18
    Its not marketed as an Apple cable, its marketed as an MFI cable. I have normal MFI lightning cables that are all black like the Anker ones. If only Anker made a Lightning to USB-C cable
     
  19. Brookzy macrumors 68040

    Brookzy

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    #19
    Come on, read the thread.

    It was established that - according to Apple - only Apple makes an official USB-C to Lightning cable.

    The next possibility was that BC Master were selling official Apple cables in their own packaging (e.g. purchased wholesale).

    But the white faceplate means it isn't an Apple cable, and therefore it is fake.
     
  20. dannys1 macrumors 68020

    dannys1

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    #20
    Is there an iOS app I can run to check this quickly? I don't fancy doing any hour long timing tests.
     
  21. masotime thread starter macrumors 68000

    masotime

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    #21
    Nope. There used to be, but Apple has since locked down iOS 10 so that such information is no longer accessible to app developers. I'm not sure if a jailbroken device would work though.
     
  22. TheRealAlex macrumors 65816

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    Sep 2, 2015
    #22
    Pumping Amps faster and faster and current into a Lithium Ion battery is not wise. It shortens its overall lifespan.
     
  23. Brookzy macrumors 68040

    Brookzy

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    #23
    The iPad Pro (12.9-inch) has a 38.5 watt hour battery. That's about the same as a 12" MacBook. The MacBook ships with a 29W adapter.

    The general principle that slower charging causes less wear does hold, but its impact is negligible.

    No-one is recommending people to go out and buy a 12W charger for your 12" MacBook to preserve its lifespan. Charging an iPad Pro at 12W is comically slow. Routinely charging it with a 29W charger is more appropriate and will not shorten its lifespan in any meaningful way.
     
  24. JTravers macrumors 6502a

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    #24
    I guess just see how long it takes to charge your iPad Pro the next time you charge it.
     
  25. butterburger cookybutter, Dec 22, 2016
    Last edited: Dec 23, 2016

    butterburger cookybutter macrumors member

    butterburger cookybutter

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    #25
    Did anyone try a Pro-C charger, since updating to iOS 10.2? Despite what has been discussed about different voltages, I think there is a chance that an update could add compatibility with MacBook Pro power supplies.

    edit add: No, I am not informed about iOS 10.2 Update. I am not making an educated guess about any software revision. I just suspect, it might be possible to "whitelist" the power supply. If iPads (Pro) could utilise a 9 V Power Delivery PS, then I doubt users will notice a difference between 29W and 27W (3A@9V) PS.
     

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