Battery Monitor for macOS

A lightweight, native macOS menu bar app that shows real-time battery charging rate, power consumption, and detailed battery health information.

Features

• Menu Bar Integration - Lives in your menu bar showing power (W) and charging rate (%/h)
• Real-time Charging Rate - Shows %/hour charging or discharging speed
• Power Details - Adapter input power, battery charging power, voltage, current
• Time Estimates - Estimated time to full charge or battery empty
• Battery Health - Health percentage, cycle count, capacity vs design capacity
• Temperature Monitoring - Real-time battery temperature
• Session Tracking - Tracks charge change since app launch
• Launch at Login - Built-in toggle to start on login (SMAppService)
• Zero Dependencies - Pure Swift, uses IOKit directly for battery data

Screenshot

Menu Bar:  5W ⚡7%/h

┌─────────────────────────────────┐
│ 🔋 Şarj Ediliyor         16%/sa │
│    14%                          │
│ [====........................]   │
│                                 │
│ Güç Detayları                   │
│ Adaptör:    20W USB-C Adapter   │
│ Adaptör:    20.0W / 20W         │
│ Pile Giden: 10.3W               │
│ Voltaj:     11.03V              │
│ Şarj Akımı: 907mA              │
│                                 │
│ Şarj Hızı                      │
│ Anlık Hız:  16.3%/saat          │
│ Tam Dolu:   5sa 23dk            │
│                                 │
│ Pil Sağlığı                    │
│ Sağlık:     91.4%              │
│ Döngü:      140 / 1000         │
│ Kapasite:   641/5551 mAh       │
│ Sıcaklık:   31.0°C             │
│                                 │
│ ◻ Başlangıçta Aç        Çıkış │
└─────────────────────────────────┘

Installation

Build from Source

Requires Xcode 16+ and macOS 14+.

git clone https://github.com/reputasyon/BatteryMonitor.git
cd BatteryMonitor
chmod +x build.sh
./build.sh

Install

cp -r BatteryMonitor.app /Applications/

Run

open /Applications/BatteryMonitor.app

The app lives in your menu bar (no Dock icon). Click the menu bar text to see details.

Auto-start on Login

Use the built-in Başlangıçta Aç toggle in the panel footer, or manually:

1. Open System Settings > General > Login Items
2. Click + and select /Applications/BatteryMonitor.app

Project Structure

Sources/BatteryMonitor/
├── main.swift              # Entry point (5 lines)
├── BatteryInfo.swift       # Data model + BatteryState enum
├── BatteryService.swift    # IOKit reading, timer, history tracking
├── BatteryPopoverView.swift # SwiftUI panel UI
└── AppDelegate.swift       # NSPanel, NSStatusItem, menu bar

File	Responsibility
BatteryInfo.swift	Battery data struct, state enum, computed properties (power, health, rates, menu bar text)
BatteryService.swift	IOKit AppleSmartBattery reading, 3-second refresh timer, sliding window rate measurement
BatteryPopoverView.swift	SwiftUI view with header, battery bar, power/rate/health sections, session info, footer
AppDelegate.swift	NSPanel positioning below status item, global click-to-dismiss, fade-in animation

How It Works

The app reads battery data directly from macOS IOKit (AppleSmartBattery) which provides:

Data	Source
Charge %	CurrentCapacity
Capacity	AppleRawCurrentCapacity / NominalChargeCapacity
Voltage	AppleRawBatteryVoltage
Current	Amperage (signed 16-bit via Int16 truncation)
Adapter	AppleRawAdapterDetails (watts, voltage, current)
Health	NominalChargeCapacity / DesignCapacity
Temperature	Temperature (centidegrees)
Cycles	CycleCount

Charging Rate Calculation

Instant Rate = (|Amperage| / MaxCapacity) * 100  →  %/hour
Power        = |Voltage * Amperage| / 1,000,000  →  Watts
Health       = MaxCapacity / DesignCapacity * 100 →  %

Architecture

• @Observable macro (Observation framework) for reactive UI updates
• @ObservationIgnored on history array to prevent unnecessary SwiftUI rebuilds
• Single timer in BatteryService with onUpdate callback to AppDelegate
• NSPanel (not NSPopover) for precise positioning below the menu bar
• nonisolated static IOKit reader for thread-safe battery access
• Int16 truncation for correct signed amperage from IOKit unsigned values

Tech Stack

• SwiftUI - Panel UI
• AppKit - Menu bar (NSStatusItem) + NSPanel
• IOKit - Native battery data access
• Observation - @Observable reactive state
• ServiceManagement - Launch at login (SMAppService)
• Swift Package Manager - Build system

License

MIT License - see LICENSE for details.