29w with new 2016 MBP

Discussion in 'MacBook Pro' started by 3pp, Dec 11, 2016.

  1. 3pp macrumors member

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    Sep 30, 2014
    #1
    Can you use a 29w MacBook power adaptor to charge (or rather maintain charge level) on a new late 2016 MacBook Pro 13". Obviously the charger it comes with is 61w and that will be my main charger but I have a spare 29w. I know it won't 'charge it' per say, not quickly anyway - but will it cause any damage using it?
     
  2. mrex, Dec 11, 2016
    Last edited: Dec 11, 2016

    mrex macrumors 68020

    mrex

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    #2
    TB uses almost max 60W (nTB max 44W) under the load, idle is for both around 8W. Rest is between those figures.

    From Apple: "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."

    https://support.apple.com/en-la/HT201700

    "You can use a higher wattage power adapter, but you cannot use one with less wattage without potential operating issues."

    https://support.apple.com/en-us/HT203207

    I dont think it is going to do any harm (but you need to ask it from Apple). the power management system in macbook will prevent the system using more energy than it gets.

    You can use your macbook either in "plugged in" or "on the battery". If the system doesnt get power enough, it is throttled. So if the system is using 35W and gets only 29W, it is impossible to maintain its functions without throttling - it cant use the battery and the charger at the same time. so if it is plugged, lets say, it gets only 29W and needed to be throttled (e.g. cpu/gpu).

    As Apple said: "but you cannot use one with less wattage without potential operating issues."

    Using a charger providing less than needed is seen as a lower performance (-> slower, laggy...)
     
  3. Larsenwork macrumors newbie

    Larsenwork

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    #3
    I charged my "13 escape version with a 10w nexus charger the other day (had to turn down screen brightness a little bit and didn't do any heavy stuff (2d graphics and web programming) so 29W will work just fine.

    Obviously won't charge as fast as the 60W
     
  4. mrex macrumors 68020

    mrex

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    #4
    Interesting.. Could you redo the same and check what stats shows?

    wattage usage and cpu stats:
    - when doing the same without plugged in
    - when doing the same but plugged in
    - under some load (plugged/unplugged)

    Is the system throttled down to maintain its functionality matching the 10W charger but obviously you didnt recognize it because there wasnt any operation needed higher wattages? It is interesting to see how much the new mbp is using while doing some light things and under some load.

    I dont have mine yet so i cant test it.
     
  5. Larsenwork macrumors newbie

    Larsenwork

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    #5
    I borrowed the 10W so I won't be able to redo the test but when I had screen at full brightness and opened a couple of cpu heavy programs it started draining the battery slowly so I'd assume it starts drawing from battery + charger instead of throttling. I'm getting the google 22W soon though so I'll be able to test with that
     
  6. mrex macrumors 68020

    mrex

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    #6
    Ok, thats new(?) then that it can use both at the same time - the battery and the charger, or did it switch entirely to the battery? If i dont remember wrong, it has been 'either or' but not possible to draw power from the both at the same time.
     
  7. jk76 macrumors member

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    Nov 27, 2016
    #7
    I have 15W USB-C chargers for Nexus 6P, and they report in System Information Power view followingly:

    AC Charger Information:
    Connected: Yes
    Wattage (W): 15
    Charging: No

    (It is not charging in this case because the battery is full.)

    My 15" MBP draws about 7-8 watts with minimum display brightness, applications running but idle, on integrated graphics. At full display brightness, power draw is about 14 watts. With this laptop, 15 W charger is barely sufficient to maintain light work, but I haven't dared to try out how long charging a battery would take, even with laptop sleeping.

    My assumption regarding "underpowered" USB-C chargers is that laptop draws as much power from them as necessary, and if the load is higher than what USB-C charger advertises to supply, battery is discharged for extra. (I base this assumption mostly on amperage readings seen on System Information Power view.)

    Behaviour with almost empty or completely empty battery is a mystery, though; my guess is that CPU may be heavily throttled, but at some point, system may simply not be able to keep in limited charger power budget (for instance, with discrete graphics powered on), and simply goes to suspend instead, until a sufficient power supply is connected...
     
  8. mrex macrumors 68020

    mrex

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    #8
    that is the thing that has been changed(?) with new macbooks if it can draw power from both power suplies at the same time. and it would be a good thing if you are out but no right charger with you, you can still plugged it in and use is without significant throttling (atleast when there is enough power in the battery).
     
  9. jk76 macrumors member

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    Nov 27, 2016
    #9
    Frankly, I'm not *certain* of this behaviour, but judging the fact these laptops can use power supplies with wattage between 10 and 100 watts, I wouldn't be surprised if this would be the case. On magsafe-based MacBooks, range of possible power supplies was much narrower...
     
  10. cerberusss macrumors 6502a

    cerberusss

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    #10
    Yes, you can use it. Just don't charge any devices off the MacBook because otherwise, it may dip into your battery. I don't really worry about that sort of thing, though.

    It won't cause any damage. Actually, USB-C Power Delivery was explicitly designed with multiple levels of wattage. The point was to make even laptops get a "trickle charge" from any USB-C charger.

    It's really, really great. I've got an Innergie 45 watt charger at my office, an iVoler charger at my client, an Anker charger at my parents' house and I only use the Apple provided one at home, for a quick charge every now and then.
     
  11. jk76 macrumors member

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    Nov 27, 2016
    #11
    The sad part about USB-C is that there's still a lot of non-compliant devices on the market, to the point of being dangerous. I was looking for a travel charger and ran into this device...

    https://plus.google.com/+BensonLeung/posts/8ceG6QwtPh7?sfc=true

    Benson Leung is really worth to check if you consider buying USB C related devices at this point from any other company than very well known brands. You will be surprised how bad the situation is, but it's not the standard that's broken...
     
  12. Larsenwork macrumors newbie

    Larsenwork

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    #12
  13. cerberusss macrumors 6502a

    cerberusss

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    #13
    Oh yeah, very true and bears repeating. Every charger I mentioned, came off his (and Nathan K.'s) list.
     
  14. 3pp thread starter macrumors member

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    Sep 30, 2014
    #14
    Thanks so much everyone for the interesting and varied discussion! Very helpful.
     
  15. chabig macrumors 68040

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    #15
    This isn't new. It has always been the case.
     
  16. AlanShutko macrumors 6502a

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    Jun 2, 2008
    #16
    No, it will only charge from one.

    • Your MacBook Pro draws power from only one power supply, even if more than one is attached—so using multiple power supplies will not speed up charging.
    • If you connect multiple power supplies to your MacBook Pro, the one that provides the most power will be used, regardless of the order in which you connected them.
     
  17. blackberrycubed macrumors 6502a

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    Feb 26, 2013
    #17
    I read somewhere that in beta 5 apple has disabled charging from the 29W brick so its possible that change will stick in the next public release.

    Currently I am able to use it to charge my non-douche bar rmbp.
     
  18. jk76 macrumors member

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    Nov 27, 2016
    #18
    This is the case. I thought the reference was to drawing power from both battery and external power supply, though.
     
  19. DBCooper macrumors newbie

    DBCooper

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    Austin, TX
    #19
    All, I tested this, I made a video, I'll post it later, but simply put:

    I was able to get the full 29W on a 13" MBP Touchbar using the 12" Macbook 29W charger. I also tested using the 87W on the 13" and it only yielded 61W. I documented this in a video I'm editing now.

    I also tested the 61W and 87W on the 12" Macbook and it only pulled the 29W. So it seems the MBP's do support the 14.5V@2A spec, it also seems the 61W and 87W support delivering 29W to the Macbook, so presumably the Macbook either supports 20.xV or these 61/87W chargers have 14.5V support in them (I haven't seen that written anywhere).
     
  20. DBCooper macrumors newbie

    DBCooper

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  21. konnyaku macrumors member

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    Dec 4, 2016
    #21
    I'm using the Apple 29W USB-C charger with my 15" 2016 Macbook Pro with Touch Bar. And yes it works.

    Under light usage the computer charges at around 15W which is enough for me. Today I used my computer on battery until around 65%. Found an outlet, plugged in, and left it alone while I grabbed lunch. By the time I was ready to work again it was nearly full.

    I work remotely and walk around every day with my laptop on my back, so I need something as light as possible. And this charger is LIGHT!
     
  22. Dogbone65 macrumors newbie

    Joined:
    Dec 23, 2016
    #22
    When you were charging did you find the 29 watt got pretty warm? I'm in same boat as you. I have a 29w I use to charge my iPad Pro when traveling and got a extra apple USB c cord to charge. Tested it at home and it charged fine but the box was pretty warm. I obviously don't want to damage my new 15" TB but would be very convenient to carry one charger for both. I only would use this to charge it back up at night.



     
  23. va1984, Dec 30, 2016
    Last edited: Dec 30, 2016

    va1984 macrumors member

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    Jan 27, 2011
    #23
    I charge my non touch bar 2016 MBP overnight using a USB port on the back of the Apple Thunderbolt Display and a USB-A to USB-C charge cable. Works a treat, but it's only 5W I think so if you use the laptop the battery actually goes down slowly. But overnight it works perfectly. I wake to find it 100% and I can keep the USB-c power brick at work or in my bag.
    Plus, as far as I know gentle slow charging is best for battery health...

    Just checked: when the thunderbolt cable is disconnected, the USB ports at the back of the ATD provide a neat little 10W to the MBP. :)
     
  24. ice29 macrumors member

    ice29

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    Dec 9, 2016
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    Switzerland
    #24
    Did anyone try the 29W adapter with 13" MBP with closed lid and external display? (with HDMI dongle) Does this work without any problems?
    I am thinking about using this adapter when on the road, since it is pretty small, but sometimes use external displays on the workplace...
     
  25. va1984 macrumors member

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    Jan 27, 2011
    #25
    will work for sure. if you do processor intensive work, though, you may it see at it just keeps the charge steady, or even loses it slowly. but that would be processor intensive work only: ordinary office/leisure laptop use, like presentations, movies, internet browsing, etc doesn't actually require much current draw. and if you can keep it plugged in over night you're sure to start the day with 100% battery (that applies to me with the 10W from the ATD, so obviously even more so for the 29W charger)
     

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