How to limit the maximum charge to 70%?

Discussion in 'MacBook Pro' started by thulium, May 1, 2016.

  1. thulium macrumors newbie

    Apr 10, 2016
    In several texts about li ion batteries you can read the recommendation not to charge about over ~70% - when you want to preserve the quality of your battery as long as possible.

    Let's assume, that is true:

    Is there a software for a MBP 13" 2015 with OS X 10.11.4 which can automatically limit the maximum charge?

    Background info: Mostly I use my MBP as a desktop computer and not mobile.

  2. iMacDragon macrumors 68000


    Oct 18, 2008
    That's for long term storage, just let it discharge at least once a month or so. No way of controlling the charger that I know of.
  3. Ries macrumors 68020

    Apr 21, 2007
    Just use it, don't bother to hassle with stuff like that, you'll properly just end up killing the battery faster. My late 2011 is mostly connected to a charger and still has 90% capacity.

    Screen Shot 2016-05-01 at 11.06.46.png
  4. T'hain Esh Kelch macrumors 601

    T'hain Esh Kelch

    Aug 5, 2001
    Yeah, you shouldn't care about that. Apple don't recommend it either, and it is their batteries.
  5. thulium thread starter macrumors newbie

    Apr 10, 2016
    Thanks for your answers.

    I'm still curious, if the statement "limiting to a charge state of 70% will detract the loss of quality of every Li Ion battery in every device" is scientifically correct or not.

    But of course it is good to know, that a battery from 2011 still has 90% of its capacity. Excellent data.
  6. zhenya macrumors 603


    Jan 6, 2005
    You are correct that best practice is to limit the time spent at full charge. In practice it may not make much difference as long as it comes off the charger a couple of times a month or so.
  7. snaky69 macrumors 603

    Mar 14, 2008
    Your battery can take care of itself much better than you ever could. No matter how much you try to baby it, it won't last any longer than it would otherwise.

    I suggest you find a more productive use of your time.
  8. TheGreenBastard macrumors 6502


    Nov 1, 2012
    Apple uses very good batteries in their machines. My Mid-2012 rMBP is sitting at 85.4% design capacity, which isn't bad imo, considering any PC I've had would stop holding charge after a year.
  9. thulium thread starter macrumors newbie

    Apr 10, 2016
    I agree with you, that baby a battery manually is a waste of time.

    Therefor I asked for a software which does the job.

    I don't agree with you, when your argument is, that it is impossible to treat a battery better than the actual software/hardware of a macbook does.

    Sure, Apple chooses a way of charging which fits for a majority of users well. I'm fine with it.
    But I'm sure, there are possibilities to treat a battery even better - in specific usecases.
    But there's no way to do so.
  10. whiteonline macrumors 6502


    Aug 19, 2011
    California, USA
    You're not going to be able to modify the charge parameters because they are firmware based.

    Keep in mind, if you abuse the battery and it fails before warranty expiration (or apple care), Apple will provide a new battery. After, you can pay to have a new one installed. The battery is a consumable.
  11. thulium thread starter macrumors newbie

    Apr 10, 2016
    Yes, I understood, that there's no interface for developers to create and offer an own charging software.
  12. matt_on_a_mtn Suspended

    Mar 25, 2016
    Why waste your time? I ask that honestly. How much longer do you actually believe you'll be able to make the battery last in the event you could somehow override the firmware, and cripple your battery life to 70%?

    Apple charges $199 for a battery replacement, and they do it while you wait. They charge even less for some models. You also have clear evidence of users in this thread having their batteries last for half a decade, while still going strong. Even if we assume your battery will fail at the 5 year mark, that's $40/year towards a brand new battery.

    That's less than a coffee a month.

    That's less than one average dinner for two at a sit down restaurant a year.

    That's less than you'd get in a spare change jar if you cashed it in yearly.

    A user above suggested finding a better use for your time, and I'd agree with that. There are better things to spend your time on than fussing with a battery that's designed for use, and set up to work as it is. And much bigger things to worry about than battery health under normal usage.
  13. thulium thread starter macrumors newbie

    Apr 10, 2016
    I'm not an electrical engineer, so I can't say how much better a battery state would/could be, when it has been treated in the discussed way.

    there are always "more important things to do".

    To be clear:
    We are all talking about hypothetical stuff. There's no interface. There's no software.

    If there would be a software offered for - let's say - 10$, the provider of the software has to convince his customers if such an investment is economically useful.
  14. TheGreenBastard macrumors 6502


    Nov 1, 2012
    It's not.
  15. matt_on_a_mtn Suspended

    Mar 25, 2016
    Hit the nail on the head.
  16. garirry macrumors 68000


    Apr 27, 2013
    Canada is my city
    I know you're paranoid, OP, but please just listen to what everyone here says and don't bother messing with your battery.
  17. electronicsguy macrumors 6502a


    Oct 12, 2015
    Pune, India
    not for MBP. Sony Vaio has a software/hardware combo in the S-series (any some other) laptops. You can set it to limit the charging to 100%, 80% or 40%
  18. CACarter1971 macrumors newbie

    Apr 28, 2016
    I'm glad I found this thread. I just got my first MBP about two weeks ago (first every notebook, actually) and read articles saying I should keep the battery between 40% and 80%, and I was being a little obsessive about it. Glad to hear that I don't really need to worry about it, because it was a real pain.
  19. throAU, May 1, 2016
    Last edited: Dec 24, 2016

    throAU macrumors 603


    Feb 13, 2012
    Perth, Western Australia
    Don't bother. My Macbook Pro from Early 2011 spent most of its life on AC and the battery is still 89-91% capacity after 5 years. At which point the GPU has died. I.e., the battery outlasted the hardware.

    If you need to use it on battery, use it on battery. If you need to use it on AC, use it on AC.
  20. Queen6 macrumors 604


    Dec 11, 2008
    Flying over the rainforest at dawn - Priceless
    Just use it and forget about it. Technically keeping the battery between 40% and 80% has some merit, equally with batteries there are a lot of variables; discharge temperature, charge temperature, discharge rates, depth of discharge etc.

    Sony & Lenovo has this type of feature, it`s really only of benefit to those who very rarely unplug from the mains. If you "baby" the notebooks battery you may get a little more life out of it, equally the battery is a consumable item, and frankly who wants to be worrying such trivia.

    In short just enjoy your Mac as intended :)

  21. myhaksown macrumors newbie

    Feb 6, 2012

    It's my understanding that we never fully charge a battery. The design capacity is what we charge to not the actual capacity (whether that's true or not I don't know). There is no software to handle it because it's a combination of your power brick, internal charging circuit, the battery, and the OS that all work together to handle it. As some others have said, there is no point in finding software because nothing by a regular developer would be anywhere near what the computer does on its own to maintain your battery. That's assuming there was separate software to do such a thing.

    I should also add that it's not software that determines when to stop charging. There is hardware with the battery (probably with the charging circuit on newer macs) that determines the designed max capacity, the actual max capacity (as a battery wears out this will degrade), and the current charge. When the charging circuit detects it's reached the actual max capacity it starts cycling (charge and discharge) to maintain the battery.
  22. RCElectricFlyer macrumors member

    May 5, 2007
    It is interesting to read all these comments about using shallower cycles and not allowing the battery to spend long periods of time at 100% SOC being a waste of time. It is well understood that Li-Ion and LiPo batteries will provide way more useable cycles and last considerably longer with shallow cycles and without spending time at 100% SOC. And here's why it really matters - batteries with this usage profile also provide considerably more energy exchange (total capacity in and out) over their lifetime.

    Temperature is also a large factor. High SOC and high temperature results in the highest rate of capacity deterioration.

    So the original request is quite valid and based on science. But of course there are disadvantages. Doing this is extremely inconvenient without software to automatically take care of it. There is something comforting about having a fully charged battery and longest run time available. And it requires a fundamental understanding on the part of the user why they might want to forgo a 100% full charge.

    Time accumulated at anything less than 4.2V/Cell which is the commonly used indication of 100% SOC in a Lithium Ion chemistry cell provides a considerable benefit in longevity. For battery longevity, there really should be an option to charge to something below 100% SOC if the portable computer is going to be connected to power for extended periods of time.
  23. otakustay macrumors newbie


    Dec 4, 2016
    You may fully charge it every time so after 5 years you get a battery with about 70% of the original capacity, or you can just carefully charge it to 70% every time in which case you get a battery with about 70% capacity all your life
  24. RCElectricFlyer macrumors member

    May 5, 2007
    Yes, and at the end of 5 years the battery charged to 70% might have 85% of its original capacity.

    Cycling ages a battery but so does time. A battery kept constantly at 100% SOC might have a capacity of 80% after 5 years and it served no useful purpose.
  25. Weaselboy Moderator


    Staff Member

    Jan 23, 2005
    Your MacBook already does this. If you check the actual power numbers in System Report or something like Coconut Battery, you will see that after the battery is fully charged it stops charging and the system will allow it to drift down to around 95% before it begins charging again. You don't see this because macOS fudges the numbers and shows it at 100% when it is not.

    Here is mine right now with Coconut Battery showing 96.9% (the true number from System Report) and the menu bar in macOS showing 100% (fudged).

    Screen Shot 2016-12-23 at 6.03.59 AM.png

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94 May 1, 2016