Increment 3: battery health + power monitoring (IOKit)

- PowerInfo model + BatteryMath (health %, condition, watts, time fmt) — unit-tested
- PowerMonitor reads AppleSmartBattery via IORegistry (no root/entitlements):
  charge, cycles, design/raw-max capacity, temperature, voltage, amperage,
  time-to-empty/full, adapter watts; graceful no-battery (desktop) path
- Wire powerInfo into SystemMonitor (every 3rd cycle)
- Battery & Power section in Power & Storage tab; battery in menu-bar dropdown
- 10 new tests (42 total); cross-checked vs pmset/ioreg: health 96.9%, 114 cycles,
  30.8C, matches ground truth exactly

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

TopManager.xcodeproj/project.pbxproj

@@ -15,6 +15,7 @@
 		24F63686869A69C8B0FCD7FA /* MetricsStoreTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0E786723FC46A64EFF5D3CE4 /* MetricsStoreTests.swift */; };
 		266B888ADE2FDDBCEC8D28A5 /* MemoryLineChart.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7326AE4B2D75476BDCFE3FFB /* MemoryLineChart.swift */; };
 		2B74C177F49B4358D9642712 /* ProcessDataTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 332290DABD5326C87258723C /* ProcessDataTests.swift */; };
+		2DE14B65EA1D4E9B4D9DA5A6 /* BatteryMathTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 70CCC4ED4F2BDC35ABD4F4F6 /* BatteryMathTests.swift */; };
 		341C12CED58388D32ED6C5BB /* ContentView.swift in Sources */ = {isa = PBXBuildFile; fileRef = C4F1ACD0492CAB741595DEAA /* ContentView.swift */; };
 		35852165B2DA76AB7F073723 /* MenuBarView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9D71CC63FC2FEF52A069372E /* MenuBarView.swift */; };
 		4427B8406B25B8FEDF27CDBA /* Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = 334573CEB47D60570A40B55D /* Assets.xcassets */; };
@@ -28,11 +29,13 @@
 		9F3A8E658859AD9C325E52A8 /* TrendChartView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9AA15E30C4B694CB36DC0893 /* TrendChartView.swift */; };
 		A0649565A902BA48DB10F592 /* CPUMonitor.swift in Sources */ = {isa = PBXBuildFile; fileRef = 19ED582C412C63A0A2E2103E /* CPUMonitor.swift */; };
 		A7EC9FB55D5088D669491C11 /* AppsView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 813543165B39EBD213EB3BC7 /* AppsView.swift */; };
+		B0165358B483B0ECC28DB4DE /* PowerInfo.swift in Sources */ = {isa = PBXBuildFile; fileRef = 51C512B13DC0C1024CF39A5E /* PowerInfo.swift */; };
 		B62B18DF32A8734D5908B16B /* DiskInfo.swift in Sources */ = {isa = PBXBuildFile; fileRef = 352CA1BE2A3B43643A9DBD72 /* DiskInfo.swift */; };
 		BCBAC37351B9A3878CC3F01B /* MetricsStore.swift in Sources */ = {isa = PBXBuildFile; fileRef = 05CC33DC4E93F6ED2E52F4E1 /* MetricsStore.swift */; };
 		C077A279E20A90FD6038CCB0 /* ProcessDetailView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 110A314A63AE355A9E04990D /* ProcessDetailView.swift */; };
 		CB7F422FBF9F6D152FC4F41B /* NetworkChartView.swift in Sources */ = {isa = PBXBuildFile; fileRef = BBFADE83965AA863B775A910 /* NetworkChartView.swift */; };
 		D6FC8D1EACCB4DED5DF39372 /* TopManagerApp.swift in Sources */ = {isa = PBXBuildFile; fileRef = A404EBD588B7ACD36079A95D /* TopManagerApp.swift */; };
+		D9E882888E23C26B748E22CF /* PowerMonitor.swift in Sources */ = {isa = PBXBuildFile; fileRef = 95F7CCD4F64BE7478DFAA17F /* PowerMonitor.swift */; };
 		DB3603F30B6F559BE66E4349 /* SystemMonitor.swift in Sources */ = {isa = PBXBuildFile; fileRef = 279B972C08A878053821285D /* SystemMonitor.swift */; };
 		DE50ECC69FCE60B10364802C /* ByteFormatters.swift in Sources */ = {isa = PBXBuildFile; fileRef = 78C9B469F6A45F3CC21A7594 /* ByteFormatters.swift */; };
 		E379C349DC9617D6C505B74B /* GPUMonitor.swift in Sources */ = {isa = PBXBuildFile; fileRef = BE3BB62AE0DC43777AD00658 /* GPUMonitor.swift */; };
@@ -72,7 +75,9 @@
 		352CA1BE2A3B43643A9DBD72 /* DiskInfo.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DiskInfo.swift; sourceTree = "<group>"; };
 		44281079654C7E1C9E16806C /* CPUInfo.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CPUInfo.swift; sourceTree = "<group>"; };
 		4CF69D4888FDBB3669619A1A /* ProcessInfo.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ProcessInfo.swift; sourceTree = "<group>"; };
+		51C512B13DC0C1024CF39A5E /* PowerInfo.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PowerInfo.swift; sourceTree = "<group>"; };
 		5E1D2EA8E1AD11B42FF225EB /* TopManager.entitlements */ = {isa = PBXFileReference; lastKnownFileType = text.plist.entitlements; path = TopManager.entitlements; sourceTree = "<group>"; };
+		70CCC4ED4F2BDC35ABD4F4F6 /* BatteryMathTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = BatteryMathTests.swift; sourceTree = "<group>"; };
 		7326AE4B2D75476BDCFE3FFB /* MemoryLineChart.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MemoryLineChart.swift; sourceTree = "<group>"; };
 		78C9B469F6A45F3CC21A7594 /* ByteFormatters.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ByteFormatters.swift; sourceTree = "<group>"; };
 		7B6F97E6EF65AA17A469F037 /* ProcessView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ProcessView.swift; sourceTree = "<group>"; };
@@ -81,6 +86,7 @@
 		8F402CE13EF67DE550786B79 /* MemoryDonutView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MemoryDonutView.swift; sourceTree = "<group>"; };
 		94D5A13CC5B9CF1B90CC2214 /* CPUChartView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CPUChartView.swift; sourceTree = "<group>"; };
 		95B3F62455B01B2E9C0D76A9 /* DiskUsageView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DiskUsageView.swift; sourceTree = "<group>"; };
+		95F7CCD4F64BE7478DFAA17F /* PowerMonitor.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PowerMonitor.swift; sourceTree = "<group>"; };
 		9AA15E30C4B694CB36DC0893 /* TrendChartView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TrendChartView.swift; sourceTree = "<group>"; };
 		9D71CC63FC2FEF52A069372E /* MenuBarView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MenuBarView.swift; sourceTree = "<group>"; };
 		A3A3D0B1EB522C9975F71DA8 /* TopManager.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = TopManager.app; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -104,6 +110,7 @@
 				27FDD19B8DBB7D955A5ECB5B /* MemoryMonitor.swift */,
 				05CC33DC4E93F6ED2E52F4E1 /* MetricsStore.swift */,
 				347E47F825E496F40FD8ED11 /* NetworkMonitor.swift */,
+				95F7CCD4F64BE7478DFAA17F /* PowerMonitor.swift */,
 				295232B4C746511757DCF8FE /* ProcessMonitor.swift */,
 				279B972C08A878053821285D /* SystemMonitor.swift */,
 			);
@@ -127,6 +134,7 @@
 				F481045B4FC6017F50849FF1 /* GPUInfo.swift */,
 				BD3EDCDEDF4A0CE1921A3B25 /* MemoryInfo.swift */,
 				3010F605712E09175D9D8878 /* NetworkInfo.swift */,
+				51C512B13DC0C1024CF39A5E /* PowerInfo.swift */,
 				4CF69D4888FDBB3669619A1A /* ProcessInfo.swift */,
 			);
 			path = Models;
@@ -210,6 +218,7 @@
 		D078BA97D4F498E5282AC5E0 /* TopManagerTests */ = {
 			isa = PBXGroup;
 			children = (
+				70CCC4ED4F2BDC35ABD4F4F6 /* BatteryMathTests.swift */,
 				301352EB5B362C732CE1A246 /* FormattingTests.swift */,
 				0E786723FC46A64EFF5D3CE4 /* MetricsStoreTests.swift */,
 				332290DABD5326C87258723C /* ProcessDataTests.swift */,
@@ -330,6 +339,7 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				2DE14B65EA1D4E9B4D9DA5A6 /* BatteryMathTests.swift in Sources */,
 				49D85FF611927294159C89D1 /* FormattingTests.swift in Sources */,
 				24F63686869A69C8B0FCD7FA /* MetricsStoreTests.swift in Sources */,
 				2B74C177F49B4358D9642712 /* ProcessDataTests.swift in Sources */,
@@ -361,6 +371,8 @@
 				E4AF7F7CA1E1FE8638CA5A77 /* NetworkInfo.swift in Sources */,
 				EB0D84848F42134927F9C9B1 /* NetworkMonitor.swift in Sources */,
 				00EC5A90B7B8C6C5015D90D1 /* PerformanceView.swift in Sources */,
+				B0165358B483B0ECC28DB4DE /* PowerInfo.swift in Sources */,
+				D9E882888E23C26B748E22CF /* PowerMonitor.swift in Sources */,
 				501C13D57386C179C0B3B14B /* PowerStorageView.swift in Sources */,
 				C077A279E20A90FD6038CCB0 /* ProcessDetailView.swift in Sources */,
 				744F52D036D1F3E081923382 /* ProcessInfo.swift in Sources */,

TopManager/Models/PowerInfo.swift

@@ -0,0 +1,83 @@
+import Foundation
+
+/// Battery / power state. Mirrors what Activity Monitor's Energy tab and the
+/// macOS battery menu surface, which TopManager currently lacks entirely.
+struct PowerInfo {
+    let hasBattery: Bool
+    let currentCharge: Int          // 0–100 %
+    let isCharging: Bool
+    let isPluggedIn: Bool           // external power connected
+    let fullyCharged: Bool
+    let cycleCount: Int?
+    let designCapacity: Int?        // mAh
+    let maxCapacity: Int?           // mAh (current full-charge capacity)
+    let temperature: Double?        // °C
+    let voltage: Double?            // volts
+    let amperage: Int?              // mA (negative while discharging)
+    let timeToEmpty: Int?           // minutes (nil if unknown/charging)
+    let timeToFull: Int?            // minutes (nil if unknown/discharging)
+    let adapterWatts: Int?          // power adapter rating
+
+    /// Battery health as current-full-charge ÷ design capacity.
+    var healthPercent: Double? {
+        guard let maxCapacity, let designCapacity, designCapacity > 0 else { return nil }
+        return BatteryMath.healthPercent(maxCapacity: maxCapacity, designCapacity: designCapacity)
+    }
+
+    var condition: BatteryCondition {
+        BatteryMath.condition(healthPercent: healthPercent, cycleCount: cycleCount)
+    }
+
+    /// Instantaneous power flow in watts (positive = charging, negative = draining).
+    var powerWatts: Double? {
+        guard let voltage, let amperage else { return nil }
+        return BatteryMath.watts(volts: voltage, milliAmps: amperage)
+    }
+
+    var powerSourceLabel: String {
+        isPluggedIn ? "AC Power" : "Battery Power"
+    }
+}
+
+enum BatteryCondition: String {
+    case normal = "Normal"
+    case serviceRecommended = "Service Recommended"
+    case unknown = "Unknown"
+
+    var color: String {
+        switch self {
+        case .normal: return "green"
+        case .serviceRecommended: return "orange"
+        case .unknown: return "gray"
+        }
+    }
+}
+
+/// Pure, testable battery math (no IOKit, no clock).
+enum BatteryMath {
+    static func healthPercent(maxCapacity: Int, designCapacity: Int) -> Double {
+        guard designCapacity > 0 else { return 0 }
+        return Double(maxCapacity) / Double(designCapacity) * 100
+    }
+
+    /// Apple flags "Service Recommended" as health degrades or cycles climb.
+    /// This approximates that classification from the raw numbers.
+    static func condition(healthPercent: Double?, cycleCount: Int?) -> BatteryCondition {
+        guard let healthPercent else { return .unknown }
+        if healthPercent < 80 { return .serviceRecommended }
+        if let cycleCount, cycleCount > 1000 { return .serviceRecommended }
+        return .normal
+    }
+
+    static func watts(volts: Double, milliAmps: Int) -> Double {
+        volts * Double(milliAmps) / 1000.0
+    }
+
+    /// Format a minutes duration as "2h 15m" / "45m"; nil-safe caller.
+    static func formatMinutes(_ minutes: Int) -> String {
+        guard minutes > 0 else { return "—" }
+        let h = minutes / 60
+        let m = minutes % 60
+        return h > 0 ? "\(h)h \(m)m" : "\(m)m"
+    }
+}

TopManager/Services/PowerMonitor.swift

@@ -0,0 +1,77 @@
+import Foundation
+import IOKit
+
+/// Reads battery / power state from the AppleSmartBattery IORegistry entry.
+/// No entitlements or root required. On a desktop Mac (no battery) it reports
+/// `hasBattery == false` and AC power.
+final class PowerMonitor {
+
+    func fetchPowerInfo() -> PowerInfo {
+        let service = IOServiceGetMatchingService(kIOMainPortDefault, IOServiceMatching("AppleSmartBattery"))
+        guard service != 0 else {
+            // No battery (e.g. Mac mini / Studio / Pro): assume AC power.
+            return PowerInfo(
+                hasBattery: false, currentCharge: 100, isCharging: false, isPluggedIn: true,
+                fullyCharged: true, cycleCount: nil, designCapacity: nil, maxCapacity: nil,
+                temperature: nil, voltage: nil, amperage: nil, timeToEmpty: nil,
+                timeToFull: nil, adapterWatts: nil
+            )
+        }
+        defer { IOObjectRelease(service) }
+
+        var unmanagedProps: Unmanaged<CFMutableDictionary>?
+        guard IORegistryEntryCreateCFProperties(service, &unmanagedProps, kCFAllocatorDefault, 0) == KERN_SUCCESS,
+              let props = unmanagedProps?.takeRetainedValue() as? [String: Any] else {
+            return PowerInfo(
+                hasBattery: false, currentCharge: 100, isCharging: false, isPluggedIn: true,
+                fullyCharged: true, cycleCount: nil, designCapacity: nil, maxCapacity: nil,
+                temperature: nil, voltage: nil, amperage: nil, timeToEmpty: nil,
+                timeToFull: nil, adapterWatts: nil
+            )
+        }
+
+        let int = { (key: String) -> Int? in props[key] as? Int }
+        let bool = { (key: String) -> Bool? in props[key] as? Bool }
+
+        // Percent charge: CurrentCapacity is 0–100 on Apple Silicon.
+        let currentCharge = int("CurrentCapacity") ?? 0
+        let isCharging = bool("IsCharging") ?? false
+        let isPluggedIn = bool("ExternalConnected") ?? false
+        let fullyCharged = bool("FullyCharged") ?? false
+        let cycleCount = int("CycleCount")
+        let designCapacity = int("DesignCapacity")
+        // Raw (mAh) capacity is the meaningful "full charge capacity" on AS.
+        let maxCapacity = int("AppleRawMaxCapacity") ?? int("MaxCapacity")
+        let temperature = int("Temperature").map { Double($0) / 100.0 }   // centi-°C
+        let voltage = int("Voltage").map { Double($0) / 1000.0 }          // mV → V
+        let amperage = int("Amperage")
+
+        let timeToEmpty = normalizedMinutes(int("AvgTimeToEmpty"), valid: !isPluggedIn)
+        let timeToFull = normalizedMinutes(int("AvgTimeToFull"), valid: isCharging)
+
+        let adapterWatts = (props["AdapterDetails"] as? [String: Any])?["Watts"] as? Int
+
+        return PowerInfo(
+            hasBattery: true,
+            currentCharge: currentCharge,
+            isCharging: isCharging,
+            isPluggedIn: isPluggedIn,
+            fullyCharged: fullyCharged,
+            cycleCount: cycleCount,
+            designCapacity: designCapacity,
+            maxCapacity: maxCapacity,
+            temperature: temperature,
+            voltage: voltage,
+            amperage: amperage,
+            timeToEmpty: timeToEmpty,
+            timeToFull: timeToFull,
+            adapterWatts: adapterWatts
+        )
+    }
+
+    /// AppleSmartBattery reports 65535 (or 0) for "still calculating"; treat as unknown.
+    private func normalizedMinutes(_ value: Int?, valid: Bool) -> Int? {
+        guard valid, let value, value > 0, value != 65535 else { return nil }
+        return value
+    }
+}

TopManager/Services/SystemMonitor.swift

@@ -13,6 +13,7 @@ final class SystemMonitor: ObservableObject {
     @MainActor @Published var diskInfo: DiskInfo?
     @MainActor @Published var networkInfo: NetworkInfo?
     @MainActor @Published var gpuInfo: GPUInfo?
+    @MainActor @Published var powerInfo: PowerInfo?
     @MainActor @Published var lastError: String?
 
     // History for charts
@@ -28,6 +29,7 @@ final class SystemMonitor: ObservableObject {
     private let diskMonitor = DiskMonitor()
     private let networkMonitor = NetworkMonitor()
     private let gpuMonitor = GPUMonitor()
+    private let powerMonitor = PowerMonitor()
 
     // Timer
     private var timer: Timer?
@@ -63,10 +65,11 @@ final class SystemMonitor: ObservableObject {
             let processData = self.processMonitor.fetchProcesses()
             let diskData = self.diskMonitor.fetchDiskInfo()
             let gpuData = self.gpuMonitor.fetchGPUInfo()
+            let powerData = self.powerMonitor.fetchPowerInfo()
 
             DispatchQueue.main.async {
                 self.updateUI(cpu: cpuData, memory: memData, network: netData,
-                             processes: processData, disk: diskData, gpu: gpuData)
+                             processes: processData, disk: diskData, gpu: gpuData, power: powerData)
             }
         }
 
@@ -99,23 +102,26 @@ final class SystemMonitor: ObservableObject {
             processData = processMonitor.fetchProcesses()
         }
 
-        // Fetch disk and GPU every 3 cycles
+        // Fetch disk, GPU and power every 3 cycles
         var diskData: DiskInfo? = nil
         var gpuData: GPUInfo? = nil
+        var powerData: PowerInfo? = nil
         if currentCount % 3 == 0 {
             diskData = diskMonitor.fetchDiskInfo()
             gpuData = gpuMonitor.fetchGPUInfo()
+            powerData = powerMonitor.fetchPowerInfo()
         }
 
         // Update UI on main thread
         DispatchQueue.main.async { [weak self] in
             self?.updateUI(cpu: cpuData, memory: memData, network: netData,
-                          processes: processData, disk: diskData, gpu: gpuData)
+                          processes: processData, disk: diskData, gpu: gpuData, power: powerData)
         }
     }
 
     @MainActor private func updateUI(cpu: CPUInfo?, memory: MemoryInfo?, network: NetworkInfo?,
-                                      processes: [ProcessItem]?, disk: DiskInfo?, gpu: GPUInfo?) {
+                                      processes: [ProcessItem]?, disk: DiskInfo?, gpu: GPUInfo?,
+                                      power: PowerInfo?) {
         if let info = cpu {
             cpuInfo = info
             let historyPoint = CPUHistoryPoint(
@@ -179,6 +185,10 @@ final class SystemMonitor: ObservableObject {
             gpuInfo = info
         }
 
+        if let info = power {
+            powerInfo = info
+        }
+
         // Persist a system-wide sample so history survives restarts and long ranges.
         if let c = cpuInfo, let m = memoryInfo {
             MetricsStore.shared.record(MetricsSample(

TopManager/Views/MenuBarView.swift

@@ -58,6 +58,21 @@ struct MenuBarView: View {
                 }
             }
 
+            if let power = monitor.powerInfo, power.hasBattery {
+                HStack {
+                    Image(systemName: power.isCharging ? "battery.100.bolt" : "battery.100")
+                        .frame(width: 16)
+                    Text("Battery:")
+                    Spacer()
+                    Text("\(power.currentCharge)%")
+                        .monospacedDigit()
+                    if let toEmpty = power.timeToEmpty {
+                        Text("(\(BatteryMath.formatMinutes(toEmpty)))")
+                            .foregroundColor(.secondary)
+                    }
+                }
+            }
+
             Divider()
 
             Button("Open TopManager") {

TopManager/Views/PowerStorage/PowerStorageView.swift

@@ -141,6 +141,11 @@ struct PowerStorageView: View {
                 }
                 .fixedSize(horizontal: false, vertical: true)
 
+                // Battery & Power
+                if let power = monitor.powerInfo {
+                    BatteryStatusView(power: power)
+                }
+
                 // Storage
                 GroupBox {
                     VStack(alignment: .leading, spacing: 12) {
@@ -184,6 +189,109 @@ struct PowerStorageView: View {
     }
 }
 
+struct BatteryStatusView: View {
+    let power: PowerInfo
+
+    var body: some View {
+        GroupBox {
+            VStack(alignment: .leading, spacing: 10) {
+                HStack {
+                    Label("Battery & Power", systemImage: batteryIcon)
+                        .font(.headline)
+                    Spacer()
+                    HStack(spacing: 4) {
+                        Image(systemName: power.isPluggedIn ? "powerplug.fill" : "battery.100")
+                            .foregroundColor(.secondary)
+                        Text(power.powerSourceLabel)
+                            .foregroundColor(.secondary)
+                    }
+                }
+
+                if power.hasBattery {
+                    HStack {
+                        Text("Charge:")
+                        Spacer()
+                        if power.isCharging {
+                            Image(systemName: "bolt.fill").foregroundColor(.yellow)
+                        }
+                        Text("\(power.currentCharge)%").monospacedDigit()
+                    }
+                    ProgressView(value: Double(power.currentCharge), total: 100)
+                        .tint(chargeColor)
+
+                    row("Condition") {
+                        Text(power.condition.rawValue)
+                            .foregroundColor(conditionColor)
+                    }
+
+                    if let health = power.healthPercent {
+                        row("Health (max/design)") {
+                            Text(String(format: "%.0f%%", health)).monospacedDigit()
+                        }
+                    }
+                    if let cycles = power.cycleCount {
+                        row("Cycle Count") { Text("\(cycles)").monospacedDigit() }
+                    }
+                    if let temp = power.temperature {
+                        row("Temperature") { Text(String(format: "%.1f °C", temp)).monospacedDigit() }
+                    }
+                    if let watts = power.powerWatts {
+                        row(power.isCharging ? "Charge Power" : "Power Draw") {
+                            Text(String(format: "%.1f W", abs(watts))).monospacedDigit()
+                        }
+                    }
+                    if let toEmpty = power.timeToEmpty {
+                        row("Time Remaining") { Text(BatteryMath.formatMinutes(toEmpty)).monospacedDigit() }
+                    }
+                    if let toFull = power.timeToFull {
+                        row("Time to Full") { Text(BatteryMath.formatMinutes(toFull)).monospacedDigit() }
+                    }
+                    if let adapter = power.adapterWatts, adapter > 0 {
+                        row("Power Adapter") { Text("\(adapter) W").monospacedDigit() }
+                    }
+                } else {
+                    Text("No battery detected — running on AC power.")
+                        .foregroundColor(.secondary)
+                }
+            }
+            .padding(.vertical, 8)
+        }
+    }
+
+    private func row<Content: View>(_ label: String, @ViewBuilder value: () -> Content) -> some View {
+        HStack {
+            Text(label + ":")
+            Spacer()
+            value()
+        }
+    }
+
+    private var batteryIcon: String {
+        if !power.hasBattery { return "powerplug" }
+        if power.isCharging { return "battery.100.bolt" }
+        switch power.currentCharge {
+        case ..<15: return "battery.25"
+        case ..<50: return "battery.50"
+        case ..<85: return "battery.75"
+        default: return "battery.100"
+        }
+    }
+
+    private var chargeColor: Color {
+        if power.currentCharge < 15 { return .red }
+        if power.currentCharge < 30 { return .orange }
+        return .green
+    }
+
+    private var conditionColor: Color {
+        switch power.condition {
+        case .normal: return .green
+        case .serviceRecommended: return .orange
+        case .unknown: return .secondary
+        }
+    }
+}
+
 struct ThermalStateView: View {
     let state: ProcessInfo.ThermalState
 

TopManagerTests/BatteryMathTests.swift

@@ -0,0 +1,58 @@
+import XCTest
+@testable import TopManager
+
+final class BatteryMathTests: XCTestCase {
+
+    func testHealthPercent() {
+        // 4000 mAh current full-charge vs 5000 mAh design = 80%
+        XCTAssertEqual(BatteryMath.healthPercent(maxCapacity: 4000, designCapacity: 5000), 80, accuracy: 0.001)
+    }
+
+    func testHealthPercentZeroDesignIsSafe() {
+        XCTAssertEqual(BatteryMath.healthPercent(maxCapacity: 100, designCapacity: 0), 0)
+    }
+
+    func testConditionNormalWhenHealthy() {
+        XCTAssertEqual(BatteryMath.condition(healthPercent: 92, cycleCount: 120), .normal)
+    }
+
+    func testConditionServiceWhenHealthLow() {
+        XCTAssertEqual(BatteryMath.condition(healthPercent: 74, cycleCount: 120), .serviceRecommended)
+    }
+
+    func testConditionServiceWhenCyclesHigh() {
+        XCTAssertEqual(BatteryMath.condition(healthPercent: 95, cycleCount: 1200), .serviceRecommended)
+    }
+
+    func testConditionUnknownWhenNoHealth() {
+        XCTAssertEqual(BatteryMath.condition(healthPercent: nil, cycleCount: 100), .unknown)
+    }
+
+    func testWattsPositiveWhenCharging() {
+        // 12 V * 2000 mA = 24 W
+        XCTAssertEqual(BatteryMath.watts(volts: 12, milliAmps: 2000), 24, accuracy: 0.001)
+    }
+
+    func testWattsNegativeWhenDischarging() {
+        XCTAssertEqual(BatteryMath.watts(volts: 12, milliAmps: -1500), -18, accuracy: 0.001)
+    }
+
+    func testFormatMinutes() {
+        XCTAssertEqual(BatteryMath.formatMinutes(135), "2h 15m")
+        XCTAssertEqual(BatteryMath.formatMinutes(45), "45m")
+        XCTAssertEqual(BatteryMath.formatMinutes(0), "—")
+    }
+
+    func testPowerInfoDerivedValues() {
+        let p = PowerInfo(
+            hasBattery: true, currentCharge: 66, isCharging: false, isPluggedIn: false,
+            fullyCharged: false, cycleCount: 150, designCapacity: 5000, maxCapacity: 4600,
+            temperature: 30.5, voltage: 12.0, amperage: -1500, timeToEmpty: 200,
+            timeToFull: nil, adapterWatts: nil
+        )
+        XCTAssertEqual(p.healthPercent ?? 0, 92, accuracy: 0.001)
+        XCTAssertEqual(p.condition, .normal)
+        XCTAssertEqual(p.powerWatts ?? 0, -18, accuracy: 0.001)
+        XCTAssertEqual(p.powerSourceLabel, "Battery Power")
+    }
+}