On my Debian 13 laptop it appears to do the right thing. Once it hits the level I specify, it stops charging and the laptop runs off AC power and doesn't charge or use the battery. But I'm setting the level via the KDE settings dialog rather than using the /sys knobs directly. Bryan On Mon, Dec 1, 2025 at 11:53 AM Robert P. J. Day via linux <linux [ at ] linux-ottawa [ dot ] org> wrote: > > On Mon, 1 Dec 2025, Robert P. J. Day via linux wrote: > > > > > (i'm using debian 13 on a dell pro max 16 laptop, but i suspect this > > question applies to any linux distro that supports battery charging > > configuration.) > > > > read recently that i shouldn't keep my laptop plugged in and maxed > > out at 100% charge perpetually since that allegedly reduces the life > > of the battery. so i read that i can play with the settings for > > battery charging under /sys/class/power_supply/BAT0: > > > > -rw-r--r-- 1 root root 4096 Dec 1 10:21 alarm > > -r--r--r-- 1 root root 4096 Nov 27 04:29 capacity > > -r--r--r-- 1 root root 4096 Dec 1 10:21 capacity_level > > -rw-r--r-- 1 root root 4096 Dec 1 10:19 charge_control_end_threshold > > -rw-r--r-- 1 root root 4096 Dec 1 10:19 charge_control_start_threshold > > -r--r--r-- 1 root root 4096 Nov 27 04:29 charge_full > > -r--r--r-- 1 root root 4096 Nov 27 04:29 charge_full_design > > -r--r--r-- 1 root root 4096 Nov 27 04:29 charge_now > > -rw-r--r-- 1 root root 4096 Dec 1 10:21 charge_types > > -r--r--r-- 1 root root 4096 Nov 27 04:29 current_now > > -r--r--r-- 1 root root 4096 Nov 27 04:29 cycle_count > > lrwxrwxrwx 1 root root 0 Nov 27 04:29 device -> ../../../PNP0C0A:00 > > -r--r--r-- 1 root root 4096 Dec 1 10:21 eppid > > drwxr-xr-x 3 root root 0 Nov 27 04:29 hwmon0 > > -r--r--r-- 1 root root 4096 Nov 27 04:29 manufacturer > > -r--r--r-- 1 root root 4096 Nov 27 04:29 model_name > > drwxr-xr-x 2 root root 0 Dec 1 10:21 power > > -r--r--r-- 1 root root 4096 Nov 27 04:29 present > > -r--r--r-- 1 root root 4096 Nov 27 04:29 serial_number > > -r--r--r-- 1 root root 4096 Nov 27 04:29 status > > lrwxrwxrwx 1 root root 0 Nov 27 04:29 subsystem -> ../../../../../../class/power_supply > > -r--r--r-- 1 root root 4096 Nov 27 04:29 technology > > -r--r--r-- 1 root root 4096 Nov 27 04:29 temp > > -r--r--r-- 1 root root 4096 Nov 27 04:29 type > > -rw-r--r-- 1 root root 4096 Nov 27 04:29 uevent > > -r--r--r-- 1 root root 4096 Nov 27 04:29 voltage_min_design > > -r--r--r-- 1 root root 4096 Nov 27 04:29 voltage_now > > > > as i read it, what i'm interested in are those early "start" and > > "end" threshold variables which are, respectively, on my system: > > > > $ cat *start* > > 75 > > $ cat *end* > > 80 > > > > as i read it, that defines a very narrow window such that, if the > > battery charge drops to 75%, it will start charging, and it will stop > > charging once it reaches 80%. in other words, if i leave the laptop > > plugged in the whole time, battery charge will bounce back and forth > > between 75% and 80%, am i reading that correctly? > > > > i ask since, with those values, my battery was at 82%, i plugged in > > the laptop, and it proceeded to charge .. 83% ... 84% ... not what i > > expected. > > > > am i missing some other config setting, perhaps one that activates > > that feature? > > > > rday > > followup ... i'm reading the documentation here: > > https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-class-power > > and even though the current value of charge_control_end_threshold is > 80, charging shows that even after charging reached 80%, it's still > charging, currently at 82%. again, not what the documentation > suggests. > > rday > > To unsubscribe send a blank message to linux+unsubscribe [ at ] linux-ottawa [ dot ] org > To get help send a blank message to linux+help [ at ] linux-ottawa [ dot ] org > To visit the archives: https://lists.linux-ottawa.org > To unsubscribe send a blank message to linux+unsubscribe [ at ] linux-ottawa [ dot ] org To get help send a blank message to linux+help [ at ] linux-ottawa [ dot ] org To visit the archives: https://lists.linux-ottawa.org