feat: track battery levels per device

2026-08-16 23:37:48 +02:00 · 2026-08-15 18:16:03 -04:00
parent b4e1f3fafe
commit 68f417575f
18 changed files with 431 additions and 373 deletions
--- a/agent/battery/battery.go
+++ b/agent/battery/battery.go
@@ -1,6 +1,13 @@
-// Package battery provides functions to check if the system has a battery and return the charge state and percentage.
+// Package battery provides battery information for the host and connected devices.
 package battery

+import (
+	"errors"
+	"sort"
+	"strconv"
+	"strings"
+)
+
 const (
 	stateUnknown uint8 = iota
 	stateEmpty
@@ -9,3 +16,55 @@ const (
 	stateDischarging
 	stateIdle
 )
+
+// Battery is a readable battery reported by the operating system.
+type Battery struct {
+	Name                  string
+	Percent               uint8
+	State                 uint8
+	FullChargeCapacity    uint64
+	HasFullChargeCapacity bool
+	System                bool
+}
+
+var errNoBatteries = errors.New("no readable batteries")
+
+// normalizeBatteries supplies stable fallback names and disambiguates duplicates.
+func normalizeBatteries(batteries []Battery) []Battery {
+	nameCounts := make(map[string]int, len(batteries))
+	for i := range batteries {
+		name := strings.TrimSpace(batteries[i].Name)
+		if name == "" {
+			name = "Battery " + strconv.Itoa(i+1)
+		}
+		nameCounts[name]++
+		if nameCounts[name] > 1 {
+			name += " (" + strconv.Itoa(nameCounts[name]) + ")"
+		}
+		batteries[i].Name = name
+	}
+	return batteries
+}
+
+// Primary returns the representative battery. Reported full-charge capacity wins,
+// then system-scoped devices, then name for deterministic ties.
+func Primary(batteries []Battery) (Battery, bool) {
+	if len(batteries) == 0 {
+		return Battery{}, false
+	}
+	ordered := append([]Battery(nil), batteries...)
+	sort.SliceStable(ordered, func(i, j int) bool {
+		a, b := ordered[i], ordered[j]
+		if a.HasFullChargeCapacity != b.HasFullChargeCapacity {
+			return a.HasFullChargeCapacity
+		}
+		if a.HasFullChargeCapacity && a.FullChargeCapacity != b.FullChargeCapacity {
+			return a.FullChargeCapacity > b.FullChargeCapacity
+		}
+		if a.System != b.System {
+			return a.System
+		}
+		return a.Name < b.Name
+	})
+	return ordered[0], true
+}
--- a/agent/battery/battery_darwin.go
+++ b/agent/battery/battery_darwin.go
@@ -3,11 +3,7 @@
 package battery

 import (
-	"errors"
-	"log/slog"
-	"math"
 	"os/exec"
-	"sync"

 	"howett.net/plist"
 )
@@ -35,62 +31,46 @@ func readMacBatteries() ([]macBattery, error) {
 	return batteries, nil
 }

-// HasReadableBattery checks if the system has a battery and returns true if it does.
-var HasReadableBattery = sync.OnceValue(func() bool {
-	systemHasBattery := false
-	batteries, err := readMacBatteries()
-	slog.Debug("Batteries", "batteries", batteries, "err", err)
-	for _, bat := range batteries {
-		if bat.MaxCapacity > 0 {
-			systemHasBattery = true
-			break
-		}
-	}
-	return systemHasBattery
-})
+func HasReadableBattery() bool {
+	batteries, _ := GetBatteryStats()
+	return len(batteries) > 0
+}

-// GetBatteryStats returns the current battery percent and charge state.
-// Uses CurrentCapacity/MaxCapacity to match the value macOS displays.
-func GetBatteryStats() (batteryPercent uint8, batteryState uint8, err error) {
-	if !HasReadableBattery() {
-		return batteryPercent, batteryState, errors.ErrUnsupported
-	}
+// GetBatteryStats returns every readable battery reported by macOS.
+func GetBatteryStats() ([]Battery, error) {
 	batteries, err := readMacBatteries()
+	if err != nil {
+		return nil, err
+	}
 	if len(batteries) == 0 {
-		return batteryPercent, batteryState, errors.New("no batteries")
+		return nil, errNoBatteries
 	}
-
-	totalCapacity := 0
-	totalCharge := 0
-	batteryState = math.MaxUint8
-
+	result := make([]Battery, 0, len(batteries))
 	for _, bat := range batteries {
-		if bat.MaxCapacity == 0 {
+		if bat.MaxCapacity <= 0 {
 			// skip ghost batteries with 0 capacity
 			// https://github.com/distatus/battery/issues/34
 			continue
 		}
-		totalCapacity += bat.MaxCapacity
-		totalCharge += min(bat.CurrentCapacity, bat.MaxCapacity)
-
+		percent := min(max(float64(bat.CurrentCapacity)/float64(bat.MaxCapacity)*100, 0), 100)
+		state := stateUnknown
 		switch {
 		case !bat.ExternalConnected:
-			batteryState = stateDischarging
+			state = stateDischarging
 		case bat.IsCharging:
-			batteryState = stateCharging
+			state = stateCharging
 		case bat.CurrentCapacity == 0:
-			batteryState = stateEmpty
+			state = stateEmpty
 		case !bat.FullyCharged:
-			batteryState = stateIdle
+			state = stateIdle
 		default:
-			batteryState = stateFull
+			state = stateFull
 		}
+		result = append(result, Battery{Name: "Primary", Percent: uint8(percent), State: state,
+			FullChargeCapacity: uint64(bat.MaxCapacity), HasFullChargeCapacity: true, System: true})
 	}
-
-	if totalCapacity == 0 || batteryState == math.MaxUint8 {
-		return batteryPercent, batteryState, errors.New("no battery capacity")
+	if len(result) == 0 {
+		return nil, errNoBatteries
 	}
-
-	batteryPercent = uint8(float64(totalCharge) / float64(totalCapacity) * 100)
-	return batteryPercent, batteryState, nil
+	return normalizeBatteries(result), nil
 }
--- a/agent/battery/battery_linux.go
+++ b/agent/battery/battery_linux.go
@@ -3,58 +3,19 @@
 package battery

 import (
-	"errors"
-	"log/slog"
-	"math"
 	"os"
 	"path/filepath"
 	"strconv"
-	"sync"

 	"github.com/henrygd/beszel/agent/utils"
 )

-// getBatteryPaths returns the paths of all batteries in /sys/class/power_supply
-var getBatteryPaths func() ([]string, error)
+var batteryRoot = "/sys/class/power_supply"

-// HasReadableBattery checks if the system has a battery and returns true if it does.
-var HasReadableBattery func() bool
-
-func init() {
-	resetBatteryState("/sys/class/power_supply")
-}
-
-// resetBatteryState resets the sync.Once functions to a fresh state.
-// Tests call this after swapping sysfsPowerSupply so the new path is picked up.
-func resetBatteryState(sysfsPowerSupplyPath string) {
-	getBatteryPaths = sync.OnceValues(func() ([]string, error) {
-		entries, err := os.ReadDir(sysfsPowerSupplyPath)
-		if err != nil {
-			return nil, err
-		}
-		var paths []string
-		for _, e := range entries {
-			path := filepath.Join(sysfsPowerSupplyPath, e.Name())
-			if utils.ReadStringFile(filepath.Join(path, "type")) == "Battery" {
-				paths = append(paths, path)
-			}
-		}
-		return paths, nil
-	})
-	HasReadableBattery = sync.OnceValue(func() bool {
-		systemHasBattery := false
-		paths, err := getBatteryPaths()
-		for _, path := range paths {
-			if _, ok := utils.ReadStringFileOK(filepath.Join(path, "capacity")); ok {
-				systemHasBattery = true
-				break
-			}
-		}
-		if !systemHasBattery {
-			slog.Debug("No battery found", "err", err)
-		}
-		return systemHasBattery
-	})
+// HasReadableBattery reports whether collection currently finds a readable battery.
+func HasReadableBattery() bool {
+	batteries, _ := GetBatteryStats()
+	return len(batteries) > 0
 }

 func parseSysfsState(status string) uint8 {
@@ -74,26 +35,18 @@ func parseSysfsState(status string) uint8 {
 	}
 }

-// GetBatteryStats returns the current battery percent and charge state.
-// Reads /sys/class/power_supply/*/capacity directly so the kernel-reported
-// value is used, which is always 0-100 and matches what the OS displays.
-func GetBatteryStats() (batteryPercent uint8, batteryState uint8, err error) {
-	if !HasReadableBattery() {
-		return batteryPercent, batteryState, errors.ErrUnsupported
-	}
-	paths, err := getBatteryPaths()
+// GetBatteryStats re-enumerates power supplies and returns every readable battery.
+func GetBatteryStats() ([]Battery, error) {
+	entries, err := os.ReadDir(batteryRoot)
 	if err != nil {
-		return batteryPercent, batteryState, err
+		return nil, err
 	}
-	if len(paths) == 0 {
-		return batteryPercent, batteryState, errors.New("no batteries")
-	}
-
-	batteryState = math.MaxUint8
-	totalPercent := 0
-	count := 0
-
-	for _, path := range paths {
+	batteries := make([]Battery, 0, len(entries))
+	for _, entry := range entries {
+		path := filepath.Join(batteryRoot, entry.Name())
+		if utils.ReadStringFile(filepath.Join(path, "type")) != "Battery" {
+			continue
+		}
 		capStr, ok := utils.ReadStringFileOK(filepath.Join(path, "capacity"))
 		if !ok {
 			continue
@@ -103,19 +56,30 @@ func GetBatteryStats() (batteryPercent uint8, batteryState uint8, err error) {
 			continue
 		}
 		cap = min(max(cap, 0), 100)
-		totalPercent += cap
-		count++
-
-		state := parseSysfsState(utils.ReadStringFile(filepath.Join(path, "status")))
-		if state != stateUnknown {
-			batteryState = state
+		name := utils.ReadStringFile(filepath.Join(path, "model_name"))
+		if name == "" {
+			name = utils.ReadStringFile(filepath.Join(path, "model"))
 		}
+		if name == "" {
+			name = entry.Name()
+		}
+		battery := Battery{
+			Name:    name,
+			Percent: uint8(cap),
+			State:   parseSysfsState(utils.ReadStringFile(filepath.Join(path, "status"))),
+			System:  utils.ReadStringFile(filepath.Join(path, "scope")) != "Device",
+		}
+		for _, fullName := range []string{"charge_full", "energy_full"} {
+			if parsed, ok := utils.ReadUintFile(filepath.Join(path, fullName)); ok && parsed > 0 {
+				battery.FullChargeCapacity = parsed
+				battery.HasFullChargeCapacity = true
+				break
+			}
+		}
+		batteries = append(batteries, battery)
 	}
-
-	if count == 0 || batteryState == math.MaxUint8 {
-		return batteryPercent, batteryState, errors.New("no battery capacity")
+	if len(batteries) == 0 {
+		return nil, errNoBatteries
 	}
-
-	batteryPercent = uint8(totalPercent / count)
-	return batteryPercent, batteryState, nil
+	return normalizeBatteries(batteries), nil
 }
--- a/agent/battery/battery_linux_test.go
+++ b/agent/battery/battery_linux_test.go
@@ -8,204 +8,102 @@ import (
 	"testing"

 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )

-// setupFakeSysfs creates a temporary sysfs-like tree under t.TempDir(),
-// swaps sysfsPowerSupply, resets the sync.Once caches, and restores
-// everything on cleanup. Returns a helper to create battery directories.
-func setupFakeSysfs(t *testing.T) (tmpDir string, addBattery func(name, capacity, status string)) {
+type fakeBattery struct{ id, name, capacity, status, full, scope string }
+
+func setupFakeSysfs(t *testing.T) (string, func(fakeBattery)) {
 	t.Helper()
-
-	tmp := t.TempDir()
-	resetBatteryState(tmp)
-
-	write := func(path, content string) {
+	root := t.TempDir()
+	previousRoot := batteryRoot
+	batteryRoot = root
+	t.Cleanup(func() { batteryRoot = previousRoot })
+	write := func(path, value string) {
 		t.Helper()
-		dir := filepath.Dir(path)
-		if err := os.MkdirAll(dir, 0o755); err != nil {
-			t.Fatal(err)
+		require.NoError(t, os.MkdirAll(filepath.Dir(path), 0o755))
+		require.NoError(t, os.WriteFile(path, []byte(value), 0o644))
+	}
+	add := func(b fakeBattery) {
+		t.Helper()
+		dir := filepath.Join(root, b.id)
+		write(filepath.Join(dir, "type"), "Battery")
+		if b.capacity != "" {
+			write(filepath.Join(dir, "capacity"), b.capacity)
 		}
-		if err := os.WriteFile(path, []byte(content), 0o644); err != nil {
-			t.Fatal(err)
+		write(filepath.Join(dir, "status"), b.status)
+		if b.name != "" {
+			write(filepath.Join(dir, "model_name"), b.name)
+		}
+		if b.full != "" {
+			write(filepath.Join(dir, "energy_full"), b.full)
+		}
+		if b.scope != "" {
+			write(filepath.Join(dir, "scope"), b.scope)
 		}
 	}
-
-	addBattery = func(name, capacity, status string) {
-		t.Helper()
-		batDir := filepath.Join(tmp, name)
-		write(filepath.Join(batDir, "type"), "Battery")
-		write(filepath.Join(batDir, "capacity"), capacity)
-		write(filepath.Join(batDir, "status"), status)
-	}
-
-	return tmp, addBattery
+	return root, add
 }

 func TestParseSysfsState(t *testing.T) {
-	tests := []struct {
-		input string
-		want  uint8
-	}{
-		{"Empty", stateEmpty},
-		{"Full", stateFull},
-		{"Charging", stateCharging},
-		{"Discharging", stateDischarging},
-		{"Not charging", stateIdle},
-		{"", stateUnknown},
-		{"SomethingElse", stateUnknown},
-	}
-	for _, tt := range tests {
-		assert.Equal(t, tt.want, parseSysfsState(tt.input), "parseSysfsState(%q)", tt.input)
-	}
+	assert.Equal(t, stateEmpty, parseSysfsState("Empty"))
+	assert.Equal(t, stateFull, parseSysfsState("Full"))
+	assert.Equal(t, stateCharging, parseSysfsState("Charging"))
+	assert.Equal(t, stateDischarging, parseSysfsState("Discharging"))
+	assert.Equal(t, stateIdle, parseSysfsState("Not charging"))
+	assert.Equal(t, stateUnknown, parseSysfsState("SomethingElse"))
 }

-func TestGetBatteryStats_SingleBattery(t *testing.T) {
-	_, addBattery := setupFakeSysfs(t)
-	addBattery("BAT0", "72", "Discharging")
-
-	pct, state, err := GetBatteryStats()
-	assert.NoError(t, err)
-	assert.Equal(t, uint8(72), pct)
-	assert.Equal(t, stateDischarging, state)
+func TestGetBatteryStatsMultipleNamedAndPrimary(t *testing.T) {
+	_, add := setupFakeSysfs(t)
+	add(fakeBattery{id: "BAT0", name: "Primary", capacity: "105", status: "Charging", full: "5000", scope: "System"})
+	add(fakeBattery{id: "hidpp_battery_0", name: "MX Keys S", capacity: "55", status: "Unknown", full: "900", scope: "Device"})
+	batteries, err := GetBatteryStats()
+	require.NoError(t, err)
+	require.Len(t, batteries, 2)
+	assert.Equal(t, "Primary", batteries[0].Name)
+	assert.Equal(t, uint8(100), batteries[0].Percent)
+	assert.Equal(t, stateUnknown, batteries[1].State)
+	primary, ok := Primary(batteries)
+	require.True(t, ok)
+	assert.Equal(t, "Primary", primary.Name)
 }

-func TestGetBatteryStats_MultipleBatteries(t *testing.T) {
-	_, addBattery := setupFakeSysfs(t)
-	addBattery("BAT0", "80", "Charging")
-	addBattery("BAT1", "40", "Charging")
-
-	pct, state, err := GetBatteryStats()
-	assert.NoError(t, err)
-	// average of 80 and 40 = 60
-	assert.EqualValues(t, 60, pct)
-	assert.Equal(t, stateCharging, state)
+func TestGetBatteryStatsFallbackDuplicatesAndUnreadable(t *testing.T) {
+	root, add := setupFakeSysfs(t)
+	add(fakeBattery{id: "BAT0", name: "Keyboard", capacity: "80", status: "Discharging"})
+	add(fakeBattery{id: "BAT1", name: "Keyboard", capacity: "-4", status: "SomethingWeird"})
+	add(fakeBattery{id: "BAT2", capacity: "not-a-number", status: "Charging"})
+	add(fakeBattery{id: "BAT3", capacity: "42", status: "Full"})
+	ac := filepath.Join(root, "AC0")
+	require.NoError(t, os.MkdirAll(ac, 0o755))
+	require.NoError(t, os.WriteFile(filepath.Join(ac, "type"), []byte("Mains"), 0o644))
+	batteries, err := GetBatteryStats()
+	require.NoError(t, err)
+	require.Len(t, batteries, 3)
+	assert.Equal(t, "Keyboard", batteries[0].Name)
+	assert.Equal(t, "Keyboard (2)", batteries[1].Name)
+	assert.Equal(t, uint8(0), batteries[1].Percent)
+	assert.Equal(t, "BAT3", batteries[2].Name)
 }

-func TestGetBatteryStats_FullBattery(t *testing.T) {
-	_, addBattery := setupFakeSysfs(t)
-	addBattery("BAT0", "100", "Full")
-
-	pct, state, err := GetBatteryStats()
-	assert.NoError(t, err)
-	assert.Equal(t, uint8(100), pct)
-	assert.Equal(t, stateFull, state)
-}
-
-func TestGetBatteryStats_CapacityClamped(t *testing.T) {
-	_, addBattery := setupFakeSysfs(t)
-	addBattery("BAT0", "105", "Charging")
-
-	pct, state, err := GetBatteryStats()
-	assert.NoError(t, err)
-	assert.Equal(t, uint8(100), pct)
-	assert.Equal(t, stateCharging, state)
-}
-
-func TestGetBatteryStats_EmptyBattery(t *testing.T) {
-	_, addBattery := setupFakeSysfs(t)
-	addBattery("BAT0", "0", "Empty")
-
-	pct, state, err := GetBatteryStats()
-	assert.NoError(t, err)
-	assert.Equal(t, uint8(0), pct)
-	assert.Equal(t, stateEmpty, state)
-}
-
-func TestGetBatteryStats_NotCharging(t *testing.T) {
-	_, addBattery := setupFakeSysfs(t)
-	addBattery("BAT0", "80", "Not charging")
-
-	pct, state, err := GetBatteryStats()
-	assert.NoError(t, err)
-	assert.Equal(t, uint8(80), pct)
-	assert.Equal(t, stateIdle, state)
-}
-
-func TestGetBatteryStats_NoBatteries(t *testing.T) {
-	setupFakeSysfs(t) // empty directory, no batteries
-
-	_, _, err := GetBatteryStats()
+func TestGetBatteryStatsHotPlugReenumerates(t *testing.T) {
+	_, add := setupFakeSysfs(t)
+	_, err := GetBatteryStats()
 	assert.Error(t, err)
-}
-
-func TestGetBatteryStats_NonBatterySupplyIgnored(t *testing.T) {
-	tmp, addBattery := setupFakeSysfs(t)
-
-	// Add a real battery
-	addBattery("BAT0", "55", "Charging")
-
-	// Add an AC adapter (type != Battery) - should be ignored
-	acDir := filepath.Join(tmp, "AC0")
-	if err := os.MkdirAll(acDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.WriteFile(filepath.Join(acDir, "type"), []byte("Mains"), 0o644); err != nil {
-		t.Fatal(err)
-	}
-
-	pct, state, err := GetBatteryStats()
-	assert.NoError(t, err)
-	assert.Equal(t, uint8(55), pct)
-	assert.Equal(t, stateCharging, state)
-}
-
-func TestGetBatteryStats_InvalidCapacitySkipped(t *testing.T) {
-	tmp, addBattery := setupFakeSysfs(t)
-
-	// One battery with valid capacity
-	addBattery("BAT0", "90", "Discharging")
-
-	// Another with invalid capacity text
-	badDir := filepath.Join(tmp, "BAT1")
-	if err := os.MkdirAll(badDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.WriteFile(filepath.Join(badDir, "type"), []byte("Battery"), 0o644); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.WriteFile(filepath.Join(badDir, "capacity"), []byte("not-a-number"), 0o644); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.WriteFile(filepath.Join(badDir, "status"), []byte("Discharging"), 0o644); err != nil {
-		t.Fatal(err)
-	}
-
-	pct, _, err := GetBatteryStats()
-	assert.NoError(t, err)
-	// Only BAT0 counted
-	assert.Equal(t, uint8(90), pct)
-}
-
-func TestGetBatteryStats_UnknownStatusOnly(t *testing.T) {
-	_, addBattery := setupFakeSysfs(t)
-	addBattery("BAT0", "50", "SomethingWeird")
-
-	_, _, err := GetBatteryStats()
-	assert.Error(t, err)
-}
-
-func TestHasReadableBattery_True(t *testing.T) {
-	_, addBattery := setupFakeSysfs(t)
-	addBattery("BAT0", "50", "Charging")
-
+	assert.False(t, HasReadableBattery())
+	add(fakeBattery{id: "BAT0", capacity: "64", status: "Discharging"})
+	batteries, err := GetBatteryStats()
+	require.NoError(t, err)
 	assert.True(t, HasReadableBattery())
+	require.Len(t, batteries, 1)
+	assert.Equal(t, uint8(64), batteries[0].Percent)
 }

-func TestHasReadableBattery_False(t *testing.T) {
-	setupFakeSysfs(t) // no batteries
-
-	assert.False(t, HasReadableBattery())
-}
-
-func TestHasReadableBattery_NoCapacityFile(t *testing.T) {
-	tmp, _ := setupFakeSysfs(t)
-
-	// Battery dir with type file but no capacity file
-	batDir := filepath.Join(tmp, "BAT0")
-	err := os.MkdirAll(batDir, 0o755)
-	assert.NoError(t, err)
-	err = os.WriteFile(filepath.Join(batDir, "type"), []byte("Battery"), 0o644)
-	assert.NoError(t, err)
-
+func TestGetBatteryStatsNoReadableCapacity(t *testing.T) {
+	_, add := setupFakeSysfs(t)
+	add(fakeBattery{id: "BAT0", status: "Charging"})
+	_, err := GetBatteryStats()
+	assert.Error(t, err)
 	assert.False(t, HasReadableBattery())
 }
--- a/agent/battery/battery_stub.go
+++ b/agent/battery/battery_stub.go
@@ -8,6 +8,6 @@ func HasReadableBattery() bool {
 	return false
 }

-func GetBatteryStats() (uint8, uint8, error) {
-	return 0, 0, errors.ErrUnsupported
+func GetBatteryStats() ([]Battery, error) {
+	return nil, errors.ErrUnsupported
 }
--- a/agent/battery/battery_test.go
+++ b/agent/battery/battery_test.go
@@ -0,0 +1,35 @@
+package battery
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPrimarySelection(t *testing.T) {
+	tests := []struct {
+		name string
+		bats []Battery
+		want string
+	}{
+		{"largest reported capacity", []Battery{{Name: "Small", FullChargeCapacity: 20, HasFullChargeCapacity: true, System: true}, {Name: "Large", FullChargeCapacity: 80, HasFullChargeCapacity: true}}, "Large"},
+		{"reported ranks over missing", []Battery{{Name: "Unknown", System: true}, {Name: "Known", FullChargeCapacity: 1, HasFullChargeCapacity: true}}, "Known"},
+		{"system wins capacity tie", []Battery{{Name: "Peripheral", FullChargeCapacity: 50, HasFullChargeCapacity: true}, {Name: "System", FullChargeCapacity: 50, HasFullChargeCapacity: true, System: true}}, "System"},
+		{"name resolves final tie", []Battery{{Name: "Zed"}, {Name: "Alpha"}}, "Alpha"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, ok := Primary(tt.bats)
+			require.True(t, ok)
+			assert.Equal(t, tt.want, got.Name)
+		})
+	}
+	_, ok := Primary(nil)
+	assert.False(t, ok)
+}
+
+func TestNormalizeBatteriesFallbackNames(t *testing.T) {
+	bats := normalizeBatteries([]Battery{{}, {}, {Name: "Mouse"}, {Name: "Mouse"}})
+	assert.Equal(t, []string{"Battery 1", "Battery 2", "Mouse", "Mouse (2)"}, []string{bats[0].Name, bats[1].Name, bats[2].Name, bats[3].Name})
+}
--- a/agent/battery/battery_windows.go
+++ b/agent/battery/battery_windows.go
@@ -7,9 +7,6 @@ package battery

 import (
 	"errors"
-	"log/slog"
-	"math"
-	"sync"
 	"syscall"
 	"unsafe"

@@ -79,7 +76,7 @@ var (
 	setupDiDestroyDeviceInfoList     = setupapi.NewProc("SetupDiDestroyDeviceInfoList")
 )

-// winBatteryGet reads one battery by index. Returns (fullCapacity, currentCapacity, state, error).
+// winBatteryGet reads one battery by index.
 // Returns error == errNotFound when there are no more batteries.
 var errNotFound = errors.New("no more batteries")

@@ -122,7 +119,7 @@ func readWinBatteryState(powerState uint32) uint8 {
 	}
 }

-func winBatteryGet(idx int) (full, current uint32, state uint8, err error) {
+func winBatteryGet(idx int) (Battery, error) {
 	hdev, err := setupDiSetup(
 		setupDiGetClassDevsW,
 		4,
@@ -132,7 +129,7 @@ func winBatteryGet(idx int) (full, current uint32, state uint8, err error) {
 		0, 0,
 	)
 	if err != nil {
-		return 0, 0, stateUnknown, err
+		return Battery{}, err
 	}
 	defer syscall.SyscallN(setupDiDestroyDeviceInfoList.Addr(), hdev)

@@ -148,10 +145,10 @@ func winBatteryGet(idx int) (full, current uint32, state uint8, err error) {
 		0,
 	)
 	if errno == 259 { // ERROR_NO_MORE_ITEMS
-		return 0, 0, stateUnknown, errNotFound
+		return Battery{}, errNotFound
 	}
 	if errno != 0 {
-		return 0, 0, stateUnknown, errno
+		return Battery{}, errno
 	}

 	var cbRequired uint32
@@ -165,7 +162,7 @@ func winBatteryGet(idx int) (full, current uint32, state uint8, err error) {
 		0,
 	)
 	if errno != 0 && errno != 122 { // ERROR_INSUFFICIENT_BUFFER
-		return 0, 0, stateUnknown, errno
+		return Battery{}, errno
 	}
 	didd := make([]uint16, cbRequired/2)
 	cbSize := (*uint32)(unsafe.Pointer(&didd[0]))
@@ -185,7 +182,7 @@ func winBatteryGet(idx int) (full, current uint32, state uint8, err error) {
 		0,
 	)
 	if errno != 0 {
-		return 0, 0, stateUnknown, errno
+		return Battery{}, errno
 	}
 	devicePath := &didd[2:][0]

@@ -199,7 +196,7 @@ func winBatteryGet(idx int) (full, current uint32, state uint8, err error) {
 		0,
 	)
 	if err != nil {
-		return 0, 0, stateUnknown, err
+		return Battery{}, err
 	}
 	defer windows.CloseHandle(handle)

@@ -216,7 +213,7 @@ func winBatteryGet(idx int) (full, current uint32, state uint8, err error) {
 		&dwOut, nil,
 	)
 	if err != nil || bqi.BatteryTag == 0 {
-		return 0, 0, stateUnknown, errors.New("battery tag not returned")
+		return Battery{}, errors.New("battery tag not returned")
 	}

 	var bi batteryInformation
@@ -229,7 +226,21 @@ func winBatteryGet(idx int) (full, current uint32, state uint8, err error) {
 		uint32(unsafe.Sizeof(bi)),
 		&dwOut, nil,
 	); err != nil {
-		return 0, 0, stateUnknown, err
+		return Battery{}, err
+	}
+
+	// BatteryDeviceName is optional, so retain the deterministic fallback on error.
+	name := ""
+	nameQuery := bqi
+	nameQuery.InformationLevel = 4 // BatteryDeviceName
+	nameBuffer := make([]uint16, 128)
+	if err := windows.DeviceIoControl(
+		handle, 2703428,
+		(*byte)(unsafe.Pointer(&nameQuery)), uint32(unsafe.Sizeof(nameQuery)),
+		(*byte)(unsafe.Pointer(&nameBuffer[0])), uint32(len(nameBuffer)*2),
+		&dwOut, nil,
+	); err == nil {
+		name = windows.UTF16ToString(nameBuffer)
 	}

 	bws := batteryWaitStatus{BatteryTag: bqi.BatteryTag}
@@ -243,56 +254,38 @@ func winBatteryGet(idx int) (full, current uint32, state uint8, err error) {
 		uint32(unsafe.Sizeof(bs)),
 		&dwOut, nil,
 	); err != nil {
-		return 0, 0, stateUnknown, err
+		return Battery{}, err
 	}

-	if bs.Capacity == 0xffffffff { // BATTERY_UNKNOWN_CAPACITY
-		return 0, 0, stateUnknown, errors.New("battery capacity unknown")
+	if bs.Capacity == 0xffffffff || bi.FullChargedCapacity == 0 || bi.FullChargedCapacity == 0xffffffff {
+		return Battery{}, errors.New("battery capacity unknown")
 	}
-
-	return bi.FullChargedCapacity, bs.Capacity, readWinBatteryState(bs.PowerState), nil
+	percent := min(float64(bs.Capacity)/float64(bi.FullChargedCapacity)*100, 100)
+	return Battery{Name: name, Percent: uint8(percent), State: readWinBatteryState(bs.PowerState),
+		FullChargeCapacity: uint64(bi.FullChargedCapacity), HasFullChargeCapacity: true, System: true}, nil
 }

 // HasReadableBattery checks if the system has a battery and returns true if it does.
-var HasReadableBattery = sync.OnceValue(func() bool {
-	systemHasBattery := false
-	full, _, _, err := winBatteryGet(0)
-	if err == nil && full > 0 {
-		systemHasBattery = true
-	}
-	if !systemHasBattery {
-		slog.Debug("No battery found", "err", err)
-	}
-	return systemHasBattery
-})
-
-// GetBatteryStats returns the current battery percent and charge state.
-func GetBatteryStats() (batteryPercent uint8, batteryState uint8, err error) {
-	if !HasReadableBattery() {
-		return batteryPercent, batteryState, errors.ErrUnsupported
-	}
-
-	totalFull := uint32(0)
-	totalCurrent := uint32(0)
-	batteryState = math.MaxUint8
+func HasReadableBattery() bool {
+	batteries, _ := GetBatteryStats()
+	return len(batteries) > 0
+}

+// GetBatteryStats returns every readable battery reported by Windows.
+func GetBatteryStats() ([]Battery, error) {
+	batteries := make([]Battery, 0, 2)
 	for i := 0; ; i++ {
-		full, current, state, bErr := winBatteryGet(i)
+		battery, bErr := winBatteryGet(i)
 		if errors.Is(bErr, errNotFound) {
 			break
 		}
-		if bErr != nil || full == 0 {
+		if bErr != nil {
 			continue
 		}
-		totalFull += full
-		totalCurrent += min(current, full)
-		batteryState = state
+		batteries = append(batteries, battery)
 	}
-
-	if totalFull == 0 || batteryState == math.MaxUint8 {
-		return batteryPercent, batteryState, errors.New("no battery capacity")
+	if len(batteries) == 0 {
+		return nil, errNoBatteries
 	}
-
-	batteryPercent = uint8(float64(totalCurrent) / float64(totalFull) * 100)
-	return batteryPercent, batteryState, nil
+	return normalizeBatteries(batteries), nil
 }
--- a/agent/system.go
+++ b/agent/system.go
@@ -132,9 +132,14 @@ func (a *Agent) getSystemStats(cacheTimeMs uint16) system.Stats {
 	var systemStats system.Stats

 	// battery
-	if batteryPercent, batteryState, err := battery.GetBatteryStats(); err == nil {
-		systemStats.Battery[0] = batteryPercent
-		systemStats.Battery[1] = batteryState
+	if batteries, err := battery.GetBatteryStats(); err == nil {
+		systemStats.Batteries = make(map[string]uint8, len(batteries))
+		for _, device := range batteries {
+			systemStats.Batteries[device.Name] = device.Percent
+		}
+		if primary, ok := battery.Primary(batteries); ok {
+			systemStats.Battery = [2]uint8{primary.Percent, primary.State}
+		}
 	}

 	// cpu metrics
--- a/internal/alerts/alerts.go
+++ b/internal/alerts/alerts.go
@@ -55,6 +55,7 @@ type SystemAlertStats struct {
 	Temperatures map[string]float32            `json:"t"`
 	LoadAvg      [3]float64                    `json:"la"`
 	Battery      [2]uint8                      `json:"bat"`
+	Batteries    map[string]uint8              `json:"bats"`
 	ExtraFs      map[string]SystemAlertFsStats `json:"efs"`
 }

--- a/internal/alerts/alerts_system.go
+++ b/internal/alerts/alerts_system.go
@@ -63,7 +63,7 @@ func (am *AlertManager) HandleSystemAlerts(systemRecord *core.Record, data *syst
 		case "GPU":
 			val = data.Info.GpuPct
 		case "Battery":
-			if data.Stats.Battery[0] == 0 {
+			if !hasRepresentativeBattery(data.Stats.Battery, data.Stats.Batteries) {
 				continue
 			}
 			val = float64(data.Stats.Battery[0])
@@ -167,6 +167,7 @@ func (am *AlertManager) HandleSystemAlerts(systemRecord *core.Record, data *syst
 		stat := systemStats[i]
 		// subtract 10 seconds to give a small time buffer
 		systemStatsCreation := stat.Created.Time().Add(-time.Second * 10)
+		stats = SystemAlertStats{}
 		if err := json.Unmarshal(stat.Stats, &stats); err != nil {
 			return err
 		}
@@ -235,6 +236,9 @@ func (am *AlertManager) HandleSystemAlerts(systemRecord *core.Record, data *syst
 				}
 				alert.val += maxUsage
 			case "Battery":
+				if !hasRepresentativeBattery(stats.Battery, stats.Batteries) {
+					continue
+				}
 				alert.val += float64(stats.Battery[0])
 			default:
 				continue
@@ -297,6 +301,10 @@ func (am *AlertManager) HandleSystemAlerts(systemRecord *core.Record, data *syst
 	return nil
 }

+func hasRepresentativeBattery(legacy [2]uint8, batteries map[string]uint8) bool {
+	return legacy != [2]uint8{} || len(batteries) > 0
+}
+
 func (am *AlertManager) sendSystemAlert(alert SystemAlertData) {
 	// log.Printf("Sending alert %s: val %f | count %d | threshold %f\n", alert.name, alert.val, alert.count, alert.threshold)
 	systemName := alert.systemRecord.GetString("name")
--- a/internal/alerts/alerts_system_test.go
+++ b/internal/alerts/alerts_system_test.go
@@ -199,7 +199,7 @@ func TestSystemAlertsOneMin(t *testing.T) {
 	testOneMinuteSystemAlert(t, "LoadAvg1", 4, setLoadAvgAlertValue, [3]float64{4.1, 0, 0}, [3]float64{3.9, 0, 0})
 	testOneMinuteSystemAlert(t, "LoadAvg5", 4, setLoadAvgAlertValue, [3]float64{0, 4.1, 0}, [3]float64{0, 3.9, 0})
 	testOneMinuteSystemAlert(t, "LoadAvg15", 4, setLoadAvgAlertValue, [3]float64{0, 0, 4.1}, [3]float64{0, 0, 3.9})
-	testOneMinuteSystemAlert(t, "Battery", 20, setBatteryAlertValue, [2]uint8{19, 0}, [2]uint8{21, 0})
+	testOneMinuteSystemAlert(t, "Battery", 20, setBatteryAlertValue, [2]uint8{0, 1}, [2]uint8{21, 0})
 }

 func TestSystemAlertsTwoMin(t *testing.T) {
--- a/internal/entities/system/system.go
+++ b/internal/entities/system/system.go
@@ -34,6 +34,7 @@ type Stats struct {
 	MaxNetworkRecv float64             `json:"nrm,omitempty" cbor:"-"`
 	Temperatures   map[string]float64  `json:"t,omitempty" cbor:"20,keyasint,omitempty"`
 	Fans           map[string]uint16   `json:"f,omitempty" cbor:"36,keyasint,omitempty"`
+	Batteries      map[string]uint8    `json:"bats,omitempty" cbor:"37,keyasint,omitempty"`
 	ExtraFs        map[string]*FsStats `json:"efs,omitempty" cbor:"21,keyasint,omitempty"`
 	GPUData        map[string]GPUData  `json:"g,omitempty" cbor:"22,keyasint,omitempty"`
 	// LoadAvg1       float64             `json:"l1,omitempty" cbor:"23,keyasint,omitempty"`
@@ -43,7 +44,7 @@ type Stats struct {
 	MaxBandwidth [2]uint64 `json:"bm,omitzero" cbor:"-"`                   // [sent bytes, recv bytes]
 	// TODO: remove other load fields in future release in favor of load avg array
 	LoadAvg           [3]float64           `json:"la,omitempty" cbor:"28,keyasint"`
-	Battery           [2]uint8             `json:"bat,omitzero" cbor:"29,keyasint,omitzero"`    // [percent, charge state, current]
+	Battery           [2]uint8             `json:"bat,omitzero" cbor:"29,keyasint,omitzero"`    // [percent, charge state]
 	NetworkInterfaces map[string][4]uint64 `json:"ni,omitempty" cbor:"31,keyasint,omitempty"`   // [upload bytes, download bytes, total upload, total download]
 	DiskIO            [2]uint64            `json:"dio,omitzero" cbor:"32,keyasint,omitzero"`    // [read bytes, write bytes]
 	MaxDiskIO         [2]uint64            `json:"diom,omitzero" cbor:"-"`                      // [max read bytes, max write bytes]
--- a/internal/entities/system/system_test.go
+++ b/internal/entities/system/system_test.go
@@ -0,0 +1,37 @@
+package system
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/fxamacker/cbor/v2"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestStatsBatteryTransport(t *testing.T) {
+	stats := Stats{Battery: [2]uint8{0, 1}, Batteries: map[string]uint8{"Primary": 0, "Mouse": 75}}
+
+	jsonData, err := json.Marshal(stats)
+	require.NoError(t, err)
+	var jsonPayload map[string]any
+	require.NoError(t, json.Unmarshal(jsonData, &jsonPayload))
+	assert.Equal(t, []any{float64(0), float64(1)}, jsonPayload["bat"])
+	assert.Equal(t, map[string]any{"Primary": float64(0), "Mouse": float64(75)}, jsonPayload["bats"])
+
+	cborData, err := cbor.Marshal(stats)
+	require.NoError(t, err)
+	var decoded Stats
+	require.NoError(t, cbor.Unmarshal(cborData, &decoded))
+	assert.Equal(t, stats.Battery, decoded.Battery)
+	assert.Equal(t, stats.Batteries, decoded.Batteries)
+}
+
+func TestStatsLegacyBatteryPayload(t *testing.T) {
+	data, err := json.Marshal(Stats{Battery: [2]uint8{50, 4}})
+	require.NoError(t, err)
+	var payload map[string]any
+	require.NoError(t, json.Unmarshal(data, &payload))
+	assert.Contains(t, payload, "bat")
+	assert.NotContains(t, payload, "bats")
+}
--- a/internal/records/records.go
+++ b/internal/records/records.go
@@ -186,6 +186,9 @@ func AverageSystemStatsSlice(records []system.Stats) system.Stats {

 	// necessary because uint8 is not big enough for the sum
 	batterySum := 0
+	batteryCount := 0
+	batterySums := make(map[string]uint64)
+	batteryCounts := make(map[string]uint64)
 	// accumulate per-core usage across records
 	var cpuCoresSums []uint64
 	// accumulate cpu breakdown [user, system, iowait, steal, idle]
@@ -232,8 +235,15 @@ func AverageSystemStatsSlice(records []system.Stats) system.Stats {
 		for i := range stats.DiskIoStats {
 			sum.DiskIoStats[i] += stats.DiskIoStats[i]
 		}
-		batterySum += int(stats.Battery[0])
-		sum.Battery[1] = stats.Battery[1]
+		if hasBattery(stats.Battery, stats.Batteries) {
+			batterySum += int(stats.Battery[0])
+			batteryCount++
+			sum.Battery[1] = stats.Battery[1]
+		}
+		for name, percent := range stats.Batteries {
+			batterySums[name] += uint64(percent)
+			batteryCounts[name]++
+		}

 		// accumulate per-core usage if present
 		if stats.CpuCoresUsage != nil {
@@ -379,7 +389,15 @@ func AverageSystemStatsSlice(records []system.Stats) system.Stats {
 	sum.LoadAvg[2] = twoDecimals(sum.LoadAvg[2] / count)
 	sum.Bandwidth[0] = sum.Bandwidth[0] / uint64(count)
 	sum.Bandwidth[1] = sum.Bandwidth[1] / uint64(count)
-	sum.Battery[0] = uint8(batterySum / int(count))
+	if batteryCount > 0 {
+		sum.Battery[0] = uint8(batterySum / batteryCount)
+	}
+	if len(batterySums) > 0 {
+		sum.Batteries = make(map[string]uint8, len(batterySums))
+		for name, total := range batterySums {
+			sum.Batteries[name] = uint8(total / batteryCounts[name])
+		}
+	}

 	// Average network interfaces
 	if sum.NetworkInterfaces != nil {
@@ -467,6 +485,10 @@ func AverageSystemStatsSlice(records []system.Stats) system.Stats {
 	return sum
 }

+func hasBattery(legacy [2]uint8, batteries map[string]uint8) bool {
+	return legacy != [2]uint8{} || len(batteries) > 0
+}
+
 // Calculate the average stats of a list of container_stats records
 func (rm *RecordManager) AverageContainerStats(db dbx.Builder, records RecordIds) []container.Stats {
 	allStats := make([][]container.Stats, 0, len(records))
--- a/internal/records/records_averaging_test.go
+++ b/internal/records/records_averaging_test.go
@@ -602,6 +602,28 @@ func TestAverageSystemStatsSlice_BatteryLastChargeState(t *testing.T) {
 	assert.Equal(t, uint8(0), result.Battery[1]) // last record's charge state
 }

+func TestAverageSystemStatsSlice_BatteriesIndependentSamples(t *testing.T) {
+	input := []system.Stats{
+		{Battery: [2]uint8{80, 4}, Batteries: map[string]uint8{"Primary": 80, "Mouse": 0}},
+		{Battery: [2]uint8{60, 3}, Batteries: map[string]uint8{"Primary": 60}},
+		{Battery: [2]uint8{30, 4}, Batteries: map[string]uint8{"Mouse": 40}},
+		{},
+	}
+	result := records.AverageSystemStatsSlice(input)
+	assert.Equal(t, map[string]uint8{"Primary": 70, "Mouse": 20}, result.Batteries)
+	assert.Equal(t, uint8(56), result.Battery[0], "representative battery excludes absent samples")
+	assert.Equal(t, uint8(4), result.Battery[1], "representative state comes from its latest sample")
+}
+
+func TestAverageSystemStatsSlice_ZeroRepresentativeBattery(t *testing.T) {
+	result := records.AverageSystemStatsSlice([]system.Stats{
+		{Battery: [2]uint8{0, 1}, Batteries: map[string]uint8{"Primary": 0}},
+		{},
+	})
+	assert.Equal(t, [2]uint8{0, 1}, result.Battery)
+	assert.Equal(t, map[string]uint8{"Primary": 0}, result.Batteries)
+}
+
 func TestAverageSystemStatsSlice_ThreeRecordsRounding(t *testing.T) {
 	input := []system.Stats{
 		{Cpu: 10.0, Mem: 8.0},
--- a/internal/site/src/components/routes/system.tsx
+++ b/internal/site/src/components/routes/system.tsx
@@ -125,7 +125,7 @@ export default memo(function SystemDetail({ id }: { id: string }) {

 					<FanChart {...coreProps} />

-					<BatteryChart {...coreProps} />
+					<BatteryChart system={system} {...coreProps} />

 					{hasGpuPowerData && <GpuPowerChart chartData={chartData} grid={grid} dataEmpty={dataEmpty} />}
 				</div>
@@ -191,7 +191,7 @@ export default memo(function SystemDetail({ id }: { id: string }) {
 						<BandwidthChart {...coreProps} systemStats={systemStats} />
 						<TemperatureChart {...coreProps} setPageBottomExtraMargin={setPageBottomExtraMargin} />
 						<FanChart {...coreProps} />
-						<BatteryChart {...coreProps} />
+						<BatteryChart system={system} {...coreProps} />
 						<SwapChart chartData={chartData} grid={grid} dataEmpty={dataEmpty} systemStats={systemStats} />
 						{pageBottomExtraMargin > 0 && <div style={{ marginBottom: pageBottomExtraMargin }}></div>}
 					</div>
--- a/internal/site/src/components/routes/system/charts/sensor-charts.tsx
+++ b/internal/site/src/components/routes/system/charts/sensor-charts.tsx
@@ -3,7 +3,7 @@ import AreaChartDefault from "@/components/charts/area-chart"
 import { batteryStateTranslations } from "@/lib/i18n"
 import { $fanFilter, $temperatureFilter, $userSettings } from "@/lib/stores"
 import { cn, decimalString, formatTemperature, toFixedFloat } from "@/lib/utils"
-import type { ChartData, SystemStatsRecord } from "@/types"
+import type { ChartData, SystemRecord, SystemStatsRecord } from "@/types"
 import { ChartCard, FilterBar } from "../chart-card"
 import LineChartDefault from "@/components/charts/line-chart"
 import { useStore } from "@nanostores/react"
@@ -14,18 +14,57 @@ export function BatteryChart({
 	grid,
 	dataEmpty,
 	maxValues,
+	system,
 }: {
 	chartData: ChartData
 	grid: boolean
 	dataEmpty: boolean
 	maxValues: boolean
+	system: SystemRecord
 }) {
-	const showBatteryChart = chartData.systemStats.at(-1)?.stats.bat
+	const batteryNames = useMemo(() => {
+		const names = new Set<string>()
+		for (const record of chartData.systemStats) {
+			for (const name of Object.keys(record.stats?.bats ?? {})) names.add(name)
+		}
+		return [...names].sort()
+	}, [chartData.systemStats])
+	const hasNamedBatteries = batteryNames.length > 0
+	const showBatteryChart = hasNamedBatteries || chartData.systemStats.some((record) => record.stats?.bat)

 	if (!showBatteryChart) {
 		return null
 	}

+	if (hasNamedBatteries) {
+		const dataPoints = batteryNames.map((name, index) => ({
+			label: name,
+			dataKey: ({ stats }: SystemStatsRecord) => stats?.bats?.[name],
+			color: `hsl(${(index * 360) / batteryNames.length}, 60%, 55%)`,
+		}))
+		return (
+			<ChartCard
+				empty={dataEmpty}
+				grid={grid}
+				title={t`Battery`}
+				description={`${t({
+					message: "Current state",
+					comment: "Context: Battery state",
+				})}: ${batteryStateTranslations[system.info.bat?.[1] ?? 0]()}`}
+			>
+				<LineChartDefault
+					chartData={chartData}
+					maxToggled={maxValues}
+					dataPoints={dataPoints}
+					domain={[0, 100]}
+					legend={true}
+					tickFormatter={(val) => `${val}%`}
+					contentFormatter={({ value }) => `${value}%`}
+				/>
+			</ChartCard>
+		)
+	}
+
 	return (
 		<ChartCard
 			empty={dataEmpty}
@@ -34,7 +73,7 @@ export function BatteryChart({
 			description={`${t({
 				message: "Current state",
 				comment: "Context: Battery state",
-			})}: ${batteryStateTranslations[chartData.systemStats.at(-1)?.stats.bat?.[1] ?? 0]()}`}
+			})}: ${batteryStateTranslations[system.info.bat?.[1] ?? 0]()}`}
 		>
 			<AreaChartDefault
 				chartData={chartData}
@@ -210,15 +249,7 @@ export function TemperatureChart({
 	)
 }

-export function FanChart({
-	chartData,
-	grid,
-	dataEmpty,
-}: {
-	chartData: ChartData
-	grid: boolean
-	dataEmpty: boolean
-}) {
+export function FanChart({ chartData, grid, dataEmpty }: { chartData: ChartData; grid: boolean; dataEmpty: boolean }) {
 	const showFanChart = chartData.systemStats.at(-1)?.stats.f

 	const filter = useStore($fanFilter)
--- a/internal/site/src/types.d.ts
+++ b/internal/site/src/types.d.ts
@@ -151,6 +151,8 @@ export interface SystemStats {
 	g?: Record<string, GPUData>
 	/** battery percent and state */
 	bat?: [number, BatteryState]
+	/** battery percentages by device name */
+	bats?: Record<string, number>
 	/** network interfaces [upload bytes, download bytes, total upload bytes, total download bytes] */
 	ni?: Record<string, [number, number, number, number]>
 }