included USB-C cable weird behaviour

Discussion in 'MacBook Pro' started by akaash00, Jul 13, 2019.

  1. akaash00 macrumors newbie

    Joined:
    Mar 25, 2016
    #1
    I bought a usb c power meter and I did an experiment.
    I noticed that with Apple's included usb-c cable charging is not stable ☹️.
    As you can see in the screenshots I took.

    In stage 1 I charged with the usb-c power meter between the Macbook and charging cable. You can see that I charge with a stable power input sitting at ~82w.
    In stage 2 I charged normally and the power input is jumping up and down with a lower overal wattage.

    The question is why this weird behaviour?
    -I think that Apple's included usb-c charging cable is not able to keep up charging with full power.
    -Buying a 100W rated usb-c/thunderbolt cable will charge with full potential and charging will better.

    Conclusion: To charge a 15" MBP the fastest with full power you need to buy a 100W rated cable.
    Shame on Apple to not include a better charging cable. They sell a Belkin thunderbolt 5A cable with support 100W for a higher price than a normal charging cable.

    Give your opinion on why Apple does this. Is this a normal behaviour or not? Are there more people who are seeing this also? Im using iStat Menus btw.
    Seems for me that it will be also safer to charge with a stable current for the batteries than swinging power input.
     

    Attached Files:

  2. DeanLubaki macrumors 6502a

    DeanLubaki

    Joined:
    May 29, 2014
    Location:
    Toronto
    #2
    Where are the screenshots of the 100w cable that is more stable at the same battery percentage of charge?
    Also you might want to use an actual USB-C v-meter instead of a software one
     
  3. jerryk macrumors 601

    Joined:
    Nov 3, 2011
    Location:
    SF Bay Area
    #3
    You sure it is not the device is not pulling let power as the battery estimated State of Charge (SOC) increases? Non-linear charging rate are better for the overall lifespan of LiIon batteries. Usually pattern is higher charge rate when SOC is low and slowing rate as battery reaches higher (SOC).

    FWIW, my Tesla starts decreasing charge rate around 50% SOC. And by 90% SOC is at 1/4-1/8 the full rate.
     
  4. akaash00, Jul 16, 2019
    Last edited: Jul 16, 2019

    akaash00 thread starter macrumors newbie

    Joined:
    Mar 25, 2016
    #4
    If you read what I wrote in Stage one I used an actual hardware usb-c V meter.
    The strange thing is when I use the meter I get a stable current, without it the Current swings up and down
    --- Post Merged, Jul 16, 2019 ---
    Again I am charging now and no this is not a decreasing charging rate. See screenshot
    that is not how batteries should charge. The current is jumping up and down. When using the hardware meter I get a normal Current.

    And I think that swinging currents generates more heat both on the battery and charging brick. Which is bad for battery life in the long term
     

    Attached Files:

  5. DeanLubaki macrumors 6502a

    DeanLubaki

    Joined:
    May 29, 2014
    Location:
    Toronto
    #5
    Then the software reporting the info is probably wrong...
    Maybe ask the developer?
     
  6. akaash00 thread starter macrumors newbie

    Joined:
    Mar 25, 2016
    #6
    No, the software reads hardware info from the macbook and is correct. The volt meter reads the same values.
     

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5 July 13, 2019