01
Set your limits
Drag the sliders to your preferred high and low thresholds. Most people pick 80% high and 20% low — the proven sweet spot for lithium-ion longevity.
Set a high and low charge limit. Keep this tab open while you work. The alarm rings the moment your battery crosses either threshold — even when the tab is in the background.
Firefox and Safari removed the Battery Status API for privacy reasons. Switch to Chrome, Edge, Brave, or Opera — or get the free desktop app below.
Get the desktop appSet it once, leave the tab open, get alerted. The whole thing takes less than a minute.
Drag the sliders to your preferred high and low thresholds. Most people pick 80% high and 20% low — the proven sweet spot for lithium-ion longevity.
Six royalty-free alarm tones, from gentle beeps to emergency sirens. Test it to make sure you'll hear it from another room.
Hit Start Monitoring. Switch tabs, work in other apps. When your battery crosses a limit, the alarm plus a system notification will get your attention.
Lithium-ion batteries lose capacity fastest when held at full charge or drained empty. Keeping your laptop between 20% and 80% can nearly double its usable lifespan.
Most laptops don't ship with a built-in charge limit, so the only way to enforce one is to unplug at the right moment. A simple alarm makes that effortless.
This is the same principle behind Tesla's daily charge limit, Apple's Optimized Battery Charging, and Lenovo's Battery Conservation Mode. Now you can apply it to any laptop with a browser tab.
Stopping at 80% reduces voltage stress on lithium-ion cells and dramatically slows long-term capacity loss.
Runs quietly in your system tray and works on every browser-less moment of your day. Free forever.
Yes. We use two techniques to ensure background reliability: a silent audio loop keeps the tab from being suspended by the browser, and OS-level browser notifications fire even if the tab is fully sleeping. For best results, click "Enable browser notifications" before you start monitoring.
Chrome, Edge, Opera, Brave, and other Chromium browsers. Firefox and Safari removed it for privacy reasons. iOS browsers don't support it. If yours is unsupported, the desktop app is the universal fallback.
Negligibly. The page is tiny and uses event-driven battery updates instead of polling. The silent audio loop that keeps the tab awake adds a fraction of a percent to CPU usage — far less than what you'd save by avoiding overcharge damage.
Browser notifications work at the operating system level, so they fire even if the tab is suspended, minimized, or your laptop screen is off. Without them, you'd only hear the alarm sound. With them, you also see a system popup that persists until dismissed.
Browsers block audio until the user interacts with the page. Click "Test" or anywhere on the page once after loading, and the alarm will play normally afterwards. Hitting "Start Monitoring" also unlocks audio.
Yes. Free to use, no signup, no credit card. The web tool and desktop app are both free forever. We may show ads, but that's it.
Your thresholds and chosen sound are saved in your browser's local storage. They persist between sessions and are never sent to our servers.