Battery charge limit with batmgt

KDE Power Management can set a charge limit, but the setting does not survive a reboot (KDE Bug 450551). The Battery Management Utility bat from tshakalekholoane/bat writes the threshold and keeps it through a systemd unit.

The battery must expose the threshold files. Check the path below. charge_control_end_threshold is required. charge_control_start_threshold is optional and some models only have the end threshold.

ls /sys/class/power_supply/BAT0

The package below is not in the official repositories or the AUR. You must update it by hand when upstream changes.

pkgname=batmgt
pkgver=1.2
pkgrel=1
pkgdesc="Battery management utility for Linux laptops (renamed to batmgt)"
arch=('x86_64')
url="https://github.com/tshakalekholoane/bat"
license=('MIT')
depends=('glibc' 'systemd')
makedepends=('go' 'make')
provides=('batmgt')
conflicts=('batmgt')
source=("https://github.com/tshakalekholoane/bat/archive/refs/tags/${pkgver}.tar.gz")
sha256sums=('241249b45659489d86cd128be38c7acde50544e3a8c08ab272468724b4e4091a')

build() {
  cd "bat-${pkgver}"

  # Set up standard Arch Linux Go build flags
  export CGO_CPPFLAGS="${CPPFLAGS}"
  export CGO_CFLAGS="${CFLAGS}"
  export CGO_CXXFLAGS="${CXXFLAGS}"
  export CGO_LDFLAGS="${LDFLAGS}"
  export GOFLAGS="-buildmode=pie -trimpath -ldflags=-linkmode=external -mod=readonly -modcacherw"

  # Build from source using Make and Go
  make build
}

package() {
  cd "bat-${pkgver}"

  # Install the compiled binary from the bin/ directory to /usr/local/bin as batmgt
  install -Dm755 bin/bat "$pkgdir/usr/local/bin/batmgt"

  # Install the systemd service, adjusting path, binary name, and target unit
  install -Dm644 bat.service "$pkgdir/usr/lib/systemd/system/batmgt.service"
  sed -i 's/\/bin\/bat/\/local\/bin\/batmgt/g' "$pkgdir/usr/lib/systemd/system/batmgt.service"
  sed -i 's/ bat / batmgt /g' "$pkgdir/usr/lib/systemd/system/batmgt.service"
  sed -i 's/{{.Event}}.target/multi-user.target/g' "$pkgdir/usr/lib/systemd/system/batmgt.service"

  # Install the man page under the new name
  install -Dm644 bat.1 "$pkgdir/usr/share/man/man1/batmgt.1"

  # Install the license file
  install -Dm644 LICENSE "$pkgdir/usr/share/licenses/$pkgname/LICENSE"
}

Create a build directory and save the PKGBUILD above as PKGBUILD inside it.
Terminal window
```
mkdir -p ~/batmgt-build && micro ~/batmgt-build/PKGBUILD
```
Build and install the package. The build downloads the source from GitHub and creates an installable .zst package.
Terminal window
```
cd ~/batmgt-build && makepkg -si
```
Set the charge limit. Replace 80 with your target percentage.
Terminal window
```
sudo batmgt threshold 80
```
Persist the limit across reboots.
Terminal window
```
sudo batmgt persist
```
Check the value written to the battery. The value should match your limit.
Terminal window
```
cat /sys/class/power_supply/BAT0/charge_control_end_threshold
```

Source: How to persist a charge limit on your laptop: bat