Power output of MBP's USB ports

Discussion in 'MacBook Pro' started by Tarek, Dec 6, 2017.

  1. Tarek macrumors 6502

    Jun 25, 2009
    Liverpool, UK
    I did some research but it seems as though people are conflicted about how much power the USB port actually provides; some people claim that the USB closest to the screen produces less power than the one farthest from it, but I'm not too sure about that theory.

    I have a 2015 13" MacBook Pro which has two USB ports, one on the right side and the other on the left side, and I would like to know the power output of the USB ports if you're going to be charging a non-Apple device (since I understand that Apple devices are able to draw more power or something). And does it really make a difference if you use the right side or the left side one? I'm inclined to believe they are identical in output.

    The reason I am asking is because I recently had to return my 1.5 months old Bose SoundSport Wireless earphones and got a brand new replacement, and I am not sure why but the battery always ran out before it was supposed to. I have a feeling it could be because I was using my Gear S3's charger but then again I use it to charge my PowerBeats 2 earphones and they seem to work fine.

    I wanted to know if it would be more practical and safer to use my MacBook to charge it instead of my Gear S3's charger? The representative at Bose told me that it would be wiser to leave it to charge for a while even AFTER the indicator turns green, but I don't understand the logic behind that.

    Thank you for your help.
  2. Brookzy macrumors 601


    May 30, 2010
    As you allude to, the documentation in this area is lacking, and even Apple's documentation is inaccurate. With so many variables it is hard to provide an answer without trying it. Generally speaking, modern Macs can provide up to 10.5W over all its USB ports simultaneously, or, for USB-C Macs, 15W over USB-C to half its ports and 7.5W to the other half simultaneously on a first-come-first-served basis.

    The best thing to do, if you can, is just try it. Plug the device in and hold down the Option key and choose Apple menu () > System Information on your Mac, and under the USB pane you can see the exact amount of power the system is providing. Then you can compare what the Mac is providing the Bose earphones compared with what it is designed to charge at.
  3. Tarek thread starter macrumors 6502

    Jun 25, 2009
    Liverpool, UK
    Thank you for your reply, @Brookzy.

    I checked the system information and this is what it said:

    Screen Shot 2017-12-07 at 11.58.03 AM.png

    And then I checked the documentation for the headset but I cannot really figure out what it is supposed to be drawing in order to charge, however I feel like 500 mA is adequate enough although should take longer.

    Screen Shot 2017-12-07 at 12.01.47 PM.png
  4. ZapNZs, Dec 7, 2017
    Last edited: Dec 7, 2017

    ZapNZs macrumors 68020


    Jan 23, 2017
    This is an interesting topic! I am very curious about this as well!

    This portion I believe I can help with. (Do note I am far from an expert on batteries.)

    In regards to many devices using lithium batteries, even when a charge indicator says that the unit is fully charged (whether that be a green LED, or a 100% message on a screen), it's not true. Often the full charge indicator presents after the fastest charge cycle of the LiCo is complete, where it has reached near full but not full capacity. (For example, a device may report full capacity at the end of stage 1.)
    Screen Shot 2017-12-07 at 7.23.28 AM.jpg

    Presumably, this is done by Makers for at least two major reasons, 1) it means a consumer can use the device faster (the rapid portion of the charge cycle is fast, and gets the battery to near full capacity, so a consumer can do a quick charge-and-go and will get nearly as long run times without waiting for the slower part of the charging process to finish), and 2) it prolongs the service life of the LiCo by not charging it to its peak voltage (where the battery is inherently at a point of greater stress.) When a consumer sees a message/indicator the charge is complete (even though it isn't) and they remove the device from charging, they may be (unknowingly) increasing the service life of that battery.
    Screen Shot 2017-12-07 at 7.20.57 AM.jpg

    (Similarly, 0% almost never means 0% [as this would ruin the battery and present a potential hazard if stored in this state for an extended period] - the device terminates functioning at a set point to preserve the service life, as the lower the depth of discharge, the shorter the service life, and most consumers will run LiCos completely empty with the incorrect belief that deep discharge = good)
    Screen Shot 2017-12-07 at 7.21.07 AM.jpg


    (TL;DR: even after the indicator turns green, it's not necessarily at a full charge.)
  5. Tarek thread starter macrumors 6502

    Jun 25, 2009
    Liverpool, UK
    Thank you for your reply, @ZapNZs. I think I might leave it charging for a while after the indicator turns green, then, and see how things go from there. I think it takes about an hour or a little bit more for it to turn green and say "100%" on the voice prompt, so I should probably give it another 30 minutes or an hour before taking it off the charger.
  6. PBG4 Dude macrumors 68020

    PBG4 Dude

    Jul 6, 2007
    Just so you know, it looks like your headphones will take up to 1A (1000mA) while charging, but your MBP is limiting current to stock USB-A spec of 0.5A (500mA). You may want to try charging your headphones using a charging brick that provides higher amperage (iPhone chargers provide 1A and iPad chargers can go up to 2.4A depending on model) and time it to see if if your headphones recharge at a significantly (~2x) faster rate.
  7. Tarek thread starter macrumors 6502

    Jun 25, 2009
    Liverpool, UK
    @PBG4 Dude I am definitely going to have to invest in a proper wall adapter in order to charge my devices quicker and more efficiently. I actually have several Samsung and Apple ones but they're all European and Egyptian so the voltage is different and I'd need some sort of a converter in order to be able to plug them in.

    I think an easier way would be to invest in an Apple USB charger (UK plug) and use it for all my devices.
  8. EugW macrumors 601


    Jun 18, 2017
    Apple's USB wall chargers are 100-240 V 50-60 Hz. I used my Canadian iPad USB charger in China, no problem. Canada is 120 V 60 Hz, China is 220 V 50 Hz.

    I was using it to charge both my iPhone and my MacBook.

    If you want to confirm the specs of your Apple chargers, just look at it. The specs are written right on the charger. (However, the text is TINY, so you may need a magnifying glass.)

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