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·
    8 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·
      5 hours 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·
      7 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·
        5 hours 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.