macOS recently introduced the feature to limit your battery to only charge up to 80%, a feature that I personally appreciate as I’m mostly using my MacBook plugged into a dock and it’s arguably a great way to limit the ageing of the unit.

There’s just one huge problem. Well, two actually. Firstly it doesn’t allow me to set a minimum charge (“start charging when battery is at X%”), so when it falls to 79% it just tops it back up to 80, not a big deal but slightly annoying. The much bigger issue is that the charge limit apparently isn’t being saved to the battery firmware itself so when the MacBook is turned off and plugged into my dock it just keeps on charging to 100%…

Similar issue with my Pixel 9 Pro, it normally sticks to the charge limit quite well, but multiple times a month I’d say it just randomly charges to 100% regardless. Apparently that’s to calibrate the battery or something? As far as I know you have to do a complete cycle to calibrate a battery which 80% to 100% isn’t, also I don’t think a Li-ion battery needs to be calibrated this often, does it?

To contrast, KDE Plasma retains the limit at all times, lets you set a minimum amount and actually tells the battery to always stop charging at that amount.

Am I just not getting something about this?

  • MonkderVierte@lemmy.zipEnglish
    0·
    3 hours ago

    Small charge cycles are the worst for the battery, so it should only charge up to charge-limit on plugging it on and then stop until it’s (let’s say 50%) lower.

    • deranger@sh.itjust.worksEnglish
      0·
      53 minutes ago

      I don’t believe you’re correct. Small discharge cycles are not at all bad for the battery.

      https://www.batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries/

      Similar to a mechanical device that wears out faster with heavy use, the depth of discharge (DoD) determines the cycle count of the battery. The smaller the discharge (low DoD), the longer the battery will last. If at all possible, avoid full discharges and charge the battery more often between uses. Partial discharge on Li-ion is fine. There is no memory and the battery does not need periodic full discharge cycles to prolong life. The exception may be a periodic calibration of the fuel gauge on a smart battery or intelligent device.

      If you look at table 2, a 10% discharge is more than 2x better in terms of longevity than a 20% discharge.

      You’re thinking of keeping the battery constantly charged at an elevated voltage, eg 90-100%. There’s nothing wrong with many small cycles. The most optimal way to use a lithium ion would be many charge cycles and the battery constantly going from 49-51%.

    • WhatAmLemmy@lemmy.worldEnglish
      0·
      2 hours ago

      Yeah. It makes me feel like the whole purpose of the limits are greenwashing. Maintaining 79-80% is probably better than 99-100%, but the former is likely only slightly better for battery longevity, when 40-80% would probably double battery longevity vs like a 10 or 20% improvement.

      • deranger@sh.itjust.worksEnglish
        0·
        43 minutes ago

        See my comment above with the battery university link, small depth of charge/discharge and frequent cycling is optimal for lithium ion batteries. The longest longevity was many 75-65% cycles, followed by 75-25%, then 85-25%, and lastly 100-25%. There’s nothing wrong with small cycles on lithium ion batteries.

  • gole@lemmy.zipEnglish
    0·
    4 hours ago

    I installed Arch on my macbook pro and simply write the maximum charge value to a file and it worked flawlessly. The macbook has great hardware. MacOS is holding it back

  • needanke@feddit.orgEnglish
    0·
    4 hours ago

    I think calibrating once a week is totally fair and honestly not that much of a draw on the system.

    • WhoIzDisIz@lemmy.todayEnglish
      0·
      3 hours ago

      That’s excessive. There’s just not that much drift in accuracy in the space of a week. Monthly would be enough.

  • BorgDrone@feddit.nlEnglish
    0·
    5 hours ago

    when the MacBook is turned off and plugged into my dock it just keeps on charging to 100%…

    Why would you ever turn it off?

      • BorgDrone@feddit.nlEnglish
        0·
        4 hours ago

        MacBooks use practically no power when in standby. Turning it off actually uses more power than leaving it on (due to the time and processing power it takes to start everything back up).

        Leaving it on also reduces wear on components. Being on all the time doesn’t cause a lot of wear, it’s switching between on and off that causes wear due to the component warming up and cooling down.

        why would you just leave it on if you’re not using it?

        We’re talking a MacBook, not a desktop Windows machine. There is no benefit to turning it off and a lot of downsides.

        • CerebralHawks@lemmy.dbzer0.comEnglish
          0·
          4 hours ago

          All of you are reading way too much into it. Turning a computer on and off doesn’t hurt it. Leaving it on all the time doesn’t hurt it either. A MacBook will last at least ten years if taken care of decently.

          As far as the battery thing, mine’s still at 100% output (not charge) after 2 years. I set the charge limit to 80% (OP is incorrect — macOS 26.4 didn’t set the charge limit to 80%, it didn’t set it to anything, it gave you the option to limit charge to 80, 85, 90, or 95% charge, or disable it if you’ve enabled it) and it’s fine, I imagine it might last a few months longer, but I don’t expect it to radically change the physics of Li-Ion battery degradation.

          Batteries are still a consumable item. MacBook batteries are generally known for their reliability and longevity, though.