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Save the Battery

A laptop's lifespan is decided by its battery. Save the Battery keeps yours healthy for longer — and features other apps charge for are all free here.

Free and open source (MIT). A macOS menu bar app for battery care, with helpers for long terminal coding sessions.

curl -fsSL https://github.com/y-minion/savethebattery/releases/latest/download/install.sh | sh

First thing: set the limit to 80% (Apple silicon, macOS 26.4 or later). The app offers Set 80% when you first open it, or pick 80% in the menu window. macOS then stops charging there, even when Save the Battery is not running.

This is a beta (0.2.0). It has been tested on one Mac so far (an M4 Pro with macOS 27.0.1). Please report problems.

Why a charge limit helps

Lithium-ion cells age faster when they sit at a high charge, and faster still when they are also warm. Apple documents a Charge Limit for this reason (support.apple.com/102338), and Battery University explains the stress curve (BU-808). Save the Battery does not promise a number of months or years. It shows what it measured on your Mac: hours spent at 90% and 95% or more, hours spent at 35 °C and 40 °C or more, cycles, and the capacity-based health estimate. The "if the limit had been 80%" comparison is a relative stress index from general Li-ion data, never a lifespan.

Features other apps charge for — all free here

• Menu bar status icon that shows charging, paused at the limit and heat hold, as icon and percent, icon only, or percent only.
• Customizable menu window: choose which sections show and in what order.
• Power flow: adapter input, battery power and what the Mac itself uses. Values it cannot read are hidden, not guessed.
• Hardware battery percentage next to the macOS percentage.
• Charge limit from 50% to 100% (below 80% needs the optional helper), plus schedules by weekday and time.
• One-time full charge, then your limit comes back.
• Heat hold: pauses charging when the battery is hot (optional, while the app runs).
• Low Power Mode switch and MagSafe LED modes (macOS default, off, or by state). Both need the optional helper.
• Health history and measured facts: daily records on your Mac only, hours at high charge and heat compared with the previous period, cycles, a capacity-based health estimate, sleep drain and suggestions. stb health --json prints them.
• Vibe-coding terminal sessions: wrap claude, codex or any command with stb run to keep the Mac awake while it works, with a time limit and screen-off option.
• Shortcuts actions: set the limit, start and end a full charge, turn the limit off, set Low Power Mode, read the battery status.
• Notifications for each event you choose, once per situation.
• English and Korean UI. It follows your macOS language.

Requirements

Your Mac	Charge limit, schedules, full charge, heat hold, Low Power Mode, MagSafe LED	Everything else
Apple silicon, macOS 26.4 or later	Yes	Yes
Apple silicon, macOS 15 to 26.3	After updating macOS to 26.4	Yes
Intel, macOS 15 or later	Not supported	Yes

The app is a universal build. On an Apple silicon Mac with an older macOS, a free macOS update to 26.4 or later turns on charge limiting. Intel Macs get everything except the charge features. The details are in docs/COMPATIBILITY.md and docs/VALIDATION.md.

Install

Terminal (recommended, no warning)

curl -fsSL https://github.com/y-minion/savethebattery/releases/latest/download/install.sh | sh

1. Press ⌘ Space, type Terminal and press Return.
2. Paste the line above with ⌘ V.
3. Press Return. Save the Battery installs into Applications and opens.

The script checks your macOS version, downloads savethebattery.zip and its checksum from the same release, verifies the SHA-256 and copies the app to /Applications without sudo. Files fetched with curl carry no quarantine flag, so macOS shows no Gatekeeper prompt. The app is not notarized (that needs the paid Apple program), so read the script before you pipe it to sh: scripts/install.sh.

Browser download

1. Download savethebattery.dmg and open it.
2. Drag Save the Battery onto the Applications folder in that window.
3. Open the app from Applications. macOS says it cannot verify the app; click Done.
4. Open System Settings › Privacy & Security, scroll down and click Open Anyway next to Save the Battery, then confirm. If step 3 showed no warning, go straight here.

You do this once. The app is signed with a free Apple Development certificate, so the signature is valid; it is just not notarized. If you open the app straight from the disk image or from Downloads, it offers to move itself into Applications.

Updates

When a new version is out, Settings › Updates shows Update now. The app downloads the release from GitHub and installs it only if the checksum matches, the app is signed by the same team (JQWWU7443A) and it is the announced newer version. Then it restarts. There is no Terminal step and no Gatekeeper prompt, and the helper stays installed. A self-built copy, or a copy outside Applications, shows the install command instead.

Safety

• Save the Battery changes nothing while AlDente, batt, battery or Battery Toolkit is installed or running. Two charge managers fighting over the same setting is a bad idea, so quit and remove the other one first.
• The charge limit is the macOS one. It stays in force when you quit the app, sleep or reboot, and you can see it in System Settings.
• The app logs the last 20 charge-setting writes it tried (time, command, who asked) in charge.json.
• Only the MagSafe LED key is ever written to the SMC. No charging SMC key is written.

The optional helper

A limit of 80% or more, schedules and the one-time full charge need no extra rights. Limits below 80%, the Low Power Mode switch and the MagSafe LED need a small root helper. The app installs it with the standard macOS administrator-password dialog, only when you choose such a feature: picking a limit below 80% offers Install helper and apply, and the Low Power Mode switch and LED install it on first use. It is never installed silently, and updates keep it; it needs reinstalling only when its protocol version changes.

• It accepts only fixed requests: write a limit, read state, read version, switch Low Power Mode, set the LED to one of four values. It runs no shell and writes one SMC key (ACLC, values 0, 1, 3, 4).
• It serves only /Applications/Save the Battery.app, run by the logged-in user, and official builds are pinned to the signing team JQWWU7443A. A self-built (ad-hoc) copy is not team-pinned, and says so.
• The protocol is version 3. If you installed the helper with 0.1.x, install it again from the app once.

More in SECURITY.md.

Uninstall

curl -fsSL https://github.com/y-minion/savethebattery/releases/latest/download/uninstall.sh | sh

It removes the app and, with the macOS password dialog, the helper (the MagSafe LED goes back to macOS). It asks before it deletes your history and settings (kept by default). If the app is running, it also asks whether to turn off the macOS charge limit (kept by default); otherwise the limit stays as it is, and you can change it in System Settings › Battery. Source: scripts/uninstall.sh.

Build from source

You need Xcode. The project is generated from project.yml with XcodeGen; run xcodegen generate after changing it.

swift test --disable-xctest
python3 scripts/smoke-sessions.py .build/debug/stb
scripts/build-app.sh
open "dist/Save the Battery.app"

scripts/build-app.sh signs with an "Apple Development" certificate from your keychain (or the one named in STB_SIGN_IDENTITY). Without one it signs ad-hoc: the app works, but the Shortcuts app will not list its actions, and the helper will not be team-pinned (a self-built copy). See CONTRIBUTING.md.

Command line

The app must be running. stb asks it to apply charge settings over a same-user local channel. The first line makes stb a shell command; add it to ~/.zshrc to keep it.

alias stb="'/Applications/Save the Battery.app/Contents/MacOS/stb'"
stb charge set 70          # 50 to 100, steps of 5
stb charge off             # turn the limit off
stb charge topup           # one-time full charge
stb charge end             # end the full charge
stb charge status --json   # also works without the app
stb health --json
stb run --hours 4 --screen-off -- claude

Exit codes: 0 success, 1 failed or unverified, 2 usage error, 3 app not running. A session's idle-sleep protection ends after its time or when the adapter is unplugged; the command itself is never killed.

Privacy

There is no telemetry and no account. History and sessions are stored only in ~/Library/Application Support/savethebattery. The app makes a daily check of api.github.com for a new version, with no identifying data; you can turn it off in Settings. It downloads a new version from GitHub only when you click Update now. Network failures are silent, and nothing is installed automatically.

More

Design notes and plans live in docs/superpowers. Release notes: docs/release-notes/0.2.0.md.

MIT · License · Third-party notices