OpenMacBattery

Open source per-app battery monitor for macOS. Find out which app is draining your MacBook's battery — looking back, not just right now.

Activity Monitor only knows the present moment. macOS's built-in Battery panel only shows the last 12 hours. OpenMacBattery remembers the past 30 days, per app.

What it does

Asks the question: "My battery dropped 40% between 02:00 and 08:00 — which app was responsible?"

• Samples every running process every 60 seconds via proc_pid_rusage (no sudo needed).
• Stores per-app energy/CPU/wakeup deltas in a local SQLite database.
• Shows live system wattage, per-app share, battery life estimate, sleep periods.
• Right-click any app → quit / force-quit / show in Activity Monitor.
• Compares current period vs previous (anomaly detection).
• Available in 8 languages.

About this project

I'm a MacBook user — not a professional software developer. I built OpenMacBattery because I wanted to answer a simple question macOS refuses to answer: "My battery dropped 40% overnight — which app was responsible?" Activity Monitor only knows the present moment, the built-in Battery panel only shows the last 12 hours, and the polished paid alternatives didn't quite fit what I needed.

So I built it for myself, substantially with the help of AI coding assistants — I want to be upfront about that. Every product decision, UX choice, and honest caveat in this README came from me; the AI did the heavy lifting on Swift, SwiftUI, IOKit, and SQLite. The result is real, working software that I run on my own MacBook every day.

I'm releasing it because once it worked for me, there was no reason to keep it private. If you're a Mac user who wants to know what's draining your battery — please use it. If you're a Swift / macOS developer who spots code that could be written better, or a native speaker who can improve one of the non-English translations, please open an issue or pull request. I'd much rather hear "here's a better way to do X" than discover it later in a crash report. That's the whole point of putting this out in public.

— Murat Dugan

Privacy

• Zero network code. No telemetry, no analytics, no cloud sync. Verify yourself: grep -r "URLSession\|http\|socket" Sources/.
• Database lives at ~/Library/Application Support/OpenMacBattery/data.db with 600 permissions (only you can read).
• Logs at ~/Library/Logs/openmacbattery.log also 600.

Requirements

• macOS 14+ (Sonoma / Sequoia / later)
• Apple Silicon (M-series) — Intel Macs work but ri_billed_energy may behave differently
• For building from source: Xcode Command Line Tools (xcode-select --install)

Download

⬇ Latest release (DMG)

1. Download OpenMacBattery-x.y.dmg
2. Open it, drag OpenMacBattery onto Applications
3. Launch from Spotlight or Launchpad
4. On first launch macOS may say "unidentified developer" — right-click the app → Open → Open. macOS remembers this.
5. Click Enable background tracking in the welcome sheet

Done. Data starts accumulating within 1–2 minutes.

Build from source

If you'd rather compile yourself:

git clone https://github.com/MuratDugan/openmacbattery.git
cd openmacbattery
./scripts/make-app.sh --install   # builds and installs to /Applications
# or
./scripts/make-dmg.sh              # produces build/OpenMacBattery-x.y.dmg

Requires Xcode Command Line Tools (xcode-select --install).

How it works

Three pieces, one binary:

1. Sampler daemon (openmacbattery daemon run) — runs in background via user LaunchAgent. Every 60 seconds, calls proc_pid_rusage(RUSAGE_INFO_V6) for every accessible process and writes deltas to SQLite. Self-throttles to 120s if a sample tick exceeds 500 ms (with hysteresis to recover when fast).
2. GUI (SwiftUI) — reads the same SQLite database read-only. Live wattage from AppleSmartBattery IORegistry entry. App icons from NSWorkspace.
3. CLI query commands — openmacbattery top, app, timeline, export, stats, prune, calibrate.

The SQLite database uses WAL mode + auto_vacuum=INCREMENTAL. Hourly aggregates are rolled up automatically; raw samples older than 7 days and aggregates older than 180 days are pruned daily at ~03:00.

Honest caveats

• ri_billed_energy is not documented to be joules. It's an Apple internal counter; we expose the raw value and apply an empirical calibration if you run openmacbattery calibrate --duration 300 (5-minute comparison against powermetrics, requires sudo). Without calibration the UI uses percentages and level badges (relative comparisons are always correct).
• System daemons may be invisible. proc_pid_rusage returns EPERM for processes you don't own (kernel_task, WindowServer, root daemons). On a single-user Mac, the gap is small.
• Sub-60 s processes are missed — if a process lives less than one sample interval, it never appears.
• Self-consumption: ~1-2 J/hour. Verified empirically — well under the 20 J/hour design target.

CLI usage

# Top consumers in a window
openmacbattery top --since 24h
openmacbattery top --since 7d --on-battery

# Per-app timeline
openmacbattery app Slack --since 7d
openmacbattery timeline --top 5 --since 24h

# Export
openmacbattery export --format csv --since 30d > out.csv
openmacbattery export --format json --app Slack

# Maintenance
openmacbattery stats
openmacbattery prune
openmacbattery daemon status

Languages

UI is localized in 8 languages. Native-speaker reviews welcome — see CONTRIBUTING.md.

Code	Language
en	English
tr	Türkçe
zh-Hans	简体中文
es	Español
de	Deutsch
fr	Français
ja	日本語
pt-BR	Português (Brasil)

The app picks up your system language automatically. Switch manually via Apple menu → Language.

Uninstall

# Stop and remove the LaunchAgent
openmacbattery daemon uninstall

# Remove the .app
rm -rf /Applications/OpenMacBattery.app

# Remove the database (loses your history!)
rm -rf "$HOME/Library/Application Support/OpenMacBattery"
rm -f "$HOME/Library/Logs/openmacbattery.log" \
      "$HOME/Library/Logs/openmacbattery.error.log"

Troubleshooting

Problem	Fix
"App can't be opened, unidentified developer" on first launch	Right-click the .app → Open → Open. macOS remembers this for next time. Standard for ad-hoc signed apps.
Sidebar empty after install	Daemon needs ≥ 2 minutes to compute the first deltas. Check with openmacbattery daemon status.
No data accumulating	Open Settings in the app and confirm Background tracking is On. If off, toggle it.
GUI looks stale	Click the refresh-ring in the toolbar (top right) or press ⌘R. Live wattage updates every 15 s; full reload every 60 s.
Energy values look strange	They are uncalibrated by default. Run openmacbattery calibrate --duration 300 (requires sudo) for joule estimates. Without calibration, percentages still rank correctly.
Can't quit a system service from the right-click menu	By design — system services (root-owned, sandboxed Apple daemons) can't be terminated by user-level processes. Use Activity Monitor with admin privileges if you really need to.
Reset everything	openmacbattery reset --confirm deletes the database and starts fresh.

Logs:

• ~/Library/Logs/openmacbattery.log — sampler heartbeat
• ~/Library/Logs/openmacbattery.error.log — errors and lifecycle events

When opening an issue, attach the error log (not the main log) and your macOS version (sw_vers).

Disclaimer

OpenMacBattery is provided "as is", with no warranty of any kind, express or implied. The author is not liable for any damage, data loss, or system issues arising from use of this software. Use at your own risk.

A few specific things to know before installing:

• The .app is ad-hoc signed, not notarized by Apple. On first launch macOS will warn you ("unidentified developer"); right-click → Open → Open to bypass. This is normal for indie open-source apps.
• The installer adds a user-level LaunchAgent at ~/Library/LaunchAgents/com.openmacbattery.plist so the sampler runs in the background. No sudo is required and no system-level changes are made — you can remove it any time with openmacbattery daemon uninstall.
• The force-quit feature uses NSRunningApplication.forceTerminate(). Like Activity Monitor's Force Quit, it can cause unsaved-changes loss in target apps. A confirmation dialog is shown for that reason.
• Energy values are estimates, not authoritative measurements. Apple's ri_billed_energy counter is undocumented; we apply optional empirical calibration but expect ±10–20 % error. Use the percentages and rankings, not absolute joule numbers, for decisions.
• The database (~/Library/Application Support/OpenMacBattery/data.db) contains a record of which apps you ran and when — don't share it publicly without redacting. Logs (~/Library/Logs/openmacbattery.log) are similar.
• This is a personal project, not a commercial product. Issues and pull requests are welcome but there's no SLA or guaranteed response time.

If something goes wrong, see Troubleshooting below or open an issue with your ~/Library/Logs/openmacbattery.error.log.

License

AGPL-3.0 — open source for personal, educational, and free-software use. Commercial vendors who modify and redistribute (or run as a SaaS service) must release their changes under the same license. This is intentional — see the project philosophy.

Why AGPL-3.0?

OpenMacBattery exists because Apple's tools cost ~$0 to write and macOS has plenty of paid utilities for similar work. The license is designed to keep this tool freely available to humans while making it uneconomic for closed-source vendors to adopt and resell. If you build commercial software on top, the AGPL forces you to open your modifications — most vendors then choose not to use it. This is by design.

Acknowledgments

Inspired by Stats, htop, and Apple's darwintests/proc_info. Built with Swift, SwiftUI, and Charts framework.

Status

v0.1 — early preview. The data layer, daemon, GUI, and i18n are functional. Needs more testing on diverse Mac configurations and native-speaker review of translations.