Macbook Pro drains battery even when connected to the power adapter

Discussion in 'MacBook Pro' started by ss.soulbeat, Feb 24, 2018.

  1. ss.soulbeat macrumors newbie

    Mar 31, 2013
    Hey guys !

    It appears the newest Macbook Pro with discrete graphics, drains power from the battery even when connected to the power adapter !!!

    Fast forward this video to 8:30 to check it out:

    Does this means you can't use the newest Macbook Pro for some hardcore gaming or other high intense discrete graphic apps for more than a couple of hours or so ???

    What if I need to use the computer all day long ?!?!

    What the heck is this ?! :(o_O

    You guys with the newest Macbook Pro have already experienced this kind of power drain ?
  2. Brookzy macrumors 601


    May 30, 2010
    This has always been the case with 15" MacBook Pros. In theory, in the 2016/17 15" model the CPU alone can consume up to 45W and the AMD graphics chip can consume a further 35W. These are theoretical maximums and in reality neither will consume that figure due to physical constraints, for example heat, and practical constraints, for example that it is unlikely both chips will be pushed to 100% constantly (especially simultaneously).

    However, that is still 80W peak. Even assuming for argument's sake that it only actually draws an average 70W at peak due to the above factors, the power drawn by the rest of the system - especially the screen if it's at high brightness - can mean the battery drains faster than the power supply can replenish it.

    For recent Macs, this seems to be handled as follows:
    • If the battery is charged, the power supply is connected, and there are no bottlenecks (e.g. overheating), the Mac will run at full performance by drawing power from both the battery and the power supply, i.e. for a total of more than 87W of power.
    • If the battery is close to being depleted, the system will throttle down slightly to ensure it uses no more than 87W of power.
    As such, when using the correct power adapter, you shouldn't have an issue in practice.
  3. Five_Oh macrumors regular


    Jan 7, 2017
    Flyover Country, USA
    2016 15 inch here with the base dGPU. I have not experienced this issue, even while gaming. I have also experienced very good battery life while using as described in the video, ~10 hours.

  4. Samuelsan2001 macrumors 604

    Oct 24, 2013
    Its always been the case with the 15 inch pro the components can draw more power than the charger can supply and this will cause a very slow battery discharge, it will of course be very slow as you are still drawing 85watts from the power supply, to be honest you will probably thermally throttle long before you run the battery out.
  5. Miltz macrumors 6502a

    Sep 6, 2013
    New York
    That video is over 1 year old using old OS so forget you even saw it. Also, I've never had this kind of issue. And I'm a "power user". Yes battery life can be short if you're using something like final cut pro the whole time, like 4-5 hours tops. Web Browsing is more like 10-12 hours.

Share This Page

4 February 24, 2018