• General
  • How Can I Limit Battery Charge to 80%

Seems to be pretty well accepted that to keep your phone battery healthy follow the 20/80 rule or something similar to it to extend life as much as possible.

Is there a FOSS privacy friendly app that stops charging at 80%? (or warn)

    The firmware already does this. It maps 0-100% to the safe operating range of the actual battery and without the messy visual of starting off with less than a full charge.

      bookreader
      That sounds interesting and would be an acceptable solution (Although I personally would prefer a toggle - there are sometimes situations where you are on the road for a long time and have no possibility to charge - and then you would like to charge to real 100%).

      I've never read this before (especially not on GrapheneOS) - do you have a source?

        Murcielago You can go and read the datasheet for any battery charger IC. Every one of them is designed to stop charging when the voltage reaches a programmable threshold. And unlike older types of batteries, lithium batteries shut off suddenly when the voltage drops below a threshold, even things like cordless drills. If you read the actual cell voltage after it shuts off, it still carries a voltage.

        Those thresholds are set in the device either by physical design (such as different resistor for controlling the thresholds) or by firmware design (programmed). Without these thresholds, the first charge would destroy the battery by overcharging it, or the first use would also destroy the battery by running it flat below the detection threshold.

        yourmother

        yourmother
        After years of use I developed a knack for timing my charging cycles, especially when it becomes a daily routine (80 to 40 lasts for 24h for me). Just try not to obsess about it bc it's still recommended to do a full charge from time to time

        bookreader Do you mean that the battery charge stops beyond 80% even though the user display shows 100%? I'm also trying to respect the 80/20 rule, do you have a source for this ?

        MAJ : Thanks for the additional explanations

        It charges to what the manufacturer deemed to be the safe optimal level. What you refer to as the "80/20 rule" is not a thing. The chemicals in batteries don't know anything about percentages. You want to charge it less because you don't believe that the hardware designer was competent at configuring their charging limits? Go right ahead and reduce your battery capacity to 60% of what it could be without accomplishing anything useful. Oh right, you get to charge it twice as often, which will shorten your battery life.

          bookreader

          numbers of charge doesn't reflect wear on battery speaking out of context. One battery cycle is 1-100%, charging 50% equals half of a cycle. What damages battery are extreme temperatures. Fast charge full cycle? Overheated. 40-80 on low W with phone turned off? U cool. And battery works more effectively in this range than on full charge or low %, meaning it lasts longer to drop 80 to 40 than e.g. from 100 to 60. Equals less charging cycles

            yourmother
            I set the alarm clock every time i plug in for charging. Its the only method i could fathom.

            I use a 5v1a adapter and that can charge the phone 10% every 23 minutes. I set the timer according to my desired charge level. You get used to it pretty fast.

            It makes sense to limit the maximum charge of a Li-ion battery to a lower voltage than the one decided by the manufacturer for people who would like to use their battery longer than what is targeted by the
            manufacturer. See the first answer to this question on stack exchange for an indepth explanation.

            I would also love such a feature but it's only possible on the official operating system as far as I know. Another cool feature would be the possibility to prevent charging above 60%, for example for using the phone as a cheap 5G router and leaving it at home always plugged to its charger.

            you could also use an external device like https://chargie.org
            it sits between the wall charger and your phone and it communicates with the phone via BT.
            in the Chargie app, you can specify values and once these valules are met, the charging stops.

            using it since years and the batteries barely degraded. i am quite happy with it
            note: i am not related with the company behind chargie or to the product in any way. i am just a happy customer

            Samsung has a feature called "Protect Battery" since Android 12 (other manufacturers may also have it). When it is switched on, the charging process stops at 85% (i.e. not only the threshold described by bookreader , but also the 85% display value).

            If you are out of range of power sockets for a longer time, you can simply deactivate "Protect Battery" beforehand and the device will charge to 100%.

            If this really helps to extend the life of the battery, I would also think it would be cool to have such a toggle on GrapheneOS.

              Murcielago
              Kindly ask to not point to bookreaders post, because it is just not true.

              If you still question if and why a li-ion battery should be operated in a range between 20% - 80% read the essay on batteryuniversity (link above)

                bookreader Why do so many manufacturers have options to limit charge to 80% though? MacBooks and iPhones both limit charge to 80% for as long as possible (until they think you're likely to remove them from the charger). OnePlus phones, Pixel phones running stock firmware, and Samsung phones all have this by default as well.

                Why does everyone do it if it's "not a thing"? Everything I've read says that batteries typically degrade more quickly as the voltage is higher, and many manufacturers seem to believe this to be true as well. While I do trust the charging circuit to behave sanely, the charging circuit ultimately has to pick some voltage and say "this is the top." I might want the top to be somewhere else. As you said, the chemistry doesn't understand percentages, so there's no magic, 100% agreed upon value for max charge voltage. This is why it makes sense for it to be configurable. If the chemistry knew about percentages, it wouldn't make any sense for it to be configurable, because there would be a universally known "correct" top voltage. But there's not.

                DaRon Many thanks for the link. My point was not so much whether his statement was right or wrong, but that I would find it practical to only charge the cell phone up to 85% and, if necessary, up to 100% by simply flipping a toggle.

                bookreader
                Can you explain it, please? For the stupid among us....
                I am really curious and interested