Hi rday, Yep — that confirms it. Your system has the standard Dell WMI modules, but not dell-wmi-battery. Without that module, the firmware simply ignores the sysfs threshold settings. Glad it’s sorted. Best, Qingwei On Mon, 1 Dec 2025 at 12:02, Robert P. J. Day <rpjday [ at ] crashcourse [ dot ] ca> wrote: > On Mon, 1 Dec 2025, Qingwei Zhang via linux wrote: > > > > > Hi rday, > > > > Your understanding of the start/end thresholds is correct — the > > battery should start charging at 75% and stop at 80%. If your Dell > > laptop keeps charging past 80%, it usually means the firmware/EC > > does not actually support Linux-controlled charge thresholds, even > > though the sysfs files exist. > > > > On many Dell models, the kernel exposes charge_control_*_threshold, > > but the hardware ignores them unless the feature is supported by the > > Dell WMI battery driver or configured directly in BIOS. > > > > A few quick checks: > > > > lsmod | grep dell > > modprobe dell-wmi-battery # if supported > > > > If dell-wmi-battery is missing (common), Linux cannot enforce > > thresholds. In that case, charging limits must be set in the BIOS > > (“Custom Charge”) if available — otherwise they cannot be > > controlled. > > > > In short: the sysfs interface is present, but your firmware isn’t > > honoring it. > > it appears that, no, that specific module is not on my system: > > /lib/modules$ find . -name dell-wmi* > ./6.12.43+deb13-amd64/kernel/drivers/platform/x86/dell/dell-wmi-sysman > > ./6.12.43+deb13-amd64/kernel/drivers/platform/x86/dell/dell-wmi-sysman/dell-wmi-sysman.ko.xz > ./6.12.43+deb13-amd64/kernel/drivers/platform/x86/dell/dell-wmi.ko.xz > ./6.12.43+deb13-amd64/kernel/drivers/platform/x86/dell/dell-wmi-led.ko.xz > ./6.12.43+deb13-amd64/kernel/drivers/platform/x86/dell/dell-wmi-ddv.ko.xz > > ./6.12.43+deb13-amd64/kernel/drivers/platform/x86/dell/dell-wmi-descriptor.ko.xz > ./6.12.43+deb13-amd64/kernel/drivers/platform/x86/dell/dell-wmi-aio.ko.xz > ./6.12.57+deb13-amd64/kernel/drivers/platform/x86/dell/dell-wmi-sysman > > ./6.12.57+deb13-amd64/kernel/drivers/platform/x86/dell/dell-wmi-sysman/dell-wmi-sysman.ko.xz > ./6.12.57+deb13-amd64/kernel/drivers/platform/x86/dell/dell-wmi.ko.xz > ./6.12.57+deb13-amd64/kernel/drivers/platform/x86/dell/dell-wmi-led.ko.xz > ./6.12.57+deb13-amd64/kernel/drivers/platform/x86/dell/dell-wmi-ddv.ko.xz > > ./6.12.57+deb13-amd64/kernel/drivers/platform/x86/dell/dell-wmi-descriptor.ko.xz > ./6.12.57+deb13-amd64/kernel/drivers/platform/x86/dell/dell-wmi-aio.ko.xz > > so that explains it, thanks. > > rday -- *Qingwei Zhang * *Software Developer (seeking opportunities) * 📍 Ottawa, Canada ✉️ zhangcfamba [ at ] gmail [ dot ] com 🌐 GitHub: qingwezhang <https://github.com/zqw86713> 🔗 LinkedIn: qingweizhang <http://www.linkedin.com/in/qingweizhang>