Battery Tester

Battery Tester - Monitor Your Device Battery Health

A comprehensive online battery testing tool that monitors your device's battery health, charging status, battery level, and performance. View real-time battery statistics, historical data, and get insights into your battery's condition using the Battery Status API. Try also our Screen Tester and Webcam Tester.

My laptop won't charge / drains instantly when unplugged — can this tool fix it?

No. This page is a read-only window onto the battery information your browser exposes through the Battery Status API — it shows level, charging state, and the browser's estimated time-to-full and time-remaining. It cannot push commands to your battery, reset firmware, recalibrate the gauge, or repair anything physical.

If your laptop will not charge or dies the moment you unplug it, the cause is one of:

1. Charger / cable — try a different known-good charger and cable; output should be at the wattage printed on your laptop.
2. Charge port / connector — debris or a damaged jack stops contact. Inspect with a light.
3. Battery itself — a worn-out cell may show 100% but hold zero charge; manufacturer diagnostics will report "Replace battery" in this state.
4. Power IC / charging circuit — board-level fault, requires a technician.
5. Firmware/EC bug — some Lenovo, HP and Dell models have a known issue where the embedded controller stops accepting charge until reset. Search "<your model> battery not charging EC reset".
6. BIOS battery threshold setting — some business laptops let you cap charging at 60% or 80% to preserve battery life; verify it is not set to a low cap.

For authoritative diagnostics, use the manufacturer's own tool: Lenovo Vantage, HP Support Assistant, Dell SupportAssist, Apple's Battery Health menu (Settings → Battery), or AccuBattery on Android. Those run at OS level and can see things the browser cannot.

How does this battery tester work?

This tool uses the Battery Status API (navigator.getBattery()) to access real-time battery information from your device:

1. Battery Level: Current charge percentage (0-100%)
2. Charging Status: Whether the device is charging or discharging
3. Charging Time: Estimated time until fully charged
4. Discharging Time: Estimated time until battery depletes
5. Historical Data: Tracks battery level changes over time

The tool automatically updates every 10 seconds and listens for battery events (charge/discharge, level changes) to provide real-time monitoring.

Note: This API is available on most laptops and some tablets, but may not work on all mobile phones or in all browsers.

Which devices and browsers support battery testing?

Battery Status API support varies by device and browser:

Supported:
- Chrome/Chromium browsers (laptops, tablets, some Android devices)
- Edge browser (Windows devices)
- Opera browser (laptops, Android devices)

Limited/No Support:
- Firefox (removed support for privacy reasons)
- Safari (not supported)
- Most iOS devices (iPhone, iPad)
- Some Android phones (depends on browser)

Best compatibility:
- Windows laptops with Chrome or Edge
- Chromebooks
- Android tablets with Chrome
- Linux laptops with Chrome/Chromium

The tool will automatically detect if the API is available and show a notification.

Does this tool read battery cycle count, design capacity, or wear level?

No — and no browser tool can. The Battery Status API exposes only four values: charge level, charging (true/false), time-to-full, and time-remaining. It has no access to design capacity, current full-charge capacity, charge cycle count, or State-of-Health (SoH). Any web page claiming to show your battery's "health %" from the browser alone is simply relabeling the current charge level — a device sitting at 30% is not a worn battery, and a worn battery freshly charged to 100% is not healthy.

That is exactly why the bar on this page is labelled "Current charge level (not capacity health)" and emits no health verdict.

To get a real SoH number, read your design capacity and current full-charge capacity from your operating system — Windows: run powercfg /batteryreport in Command Prompt; macOS: coconutBattery or System Information; Linux: upower -i /org/freedesktop/UPower/devices/battery_BAT0 — then type those values into the Capacity health estimator on this page. It computes SoH = current ÷ design, estimates remaining cycles, and stamps a PASS / MARGINAL / FAIL verdict against your chosen threshold (industry End-Of-Life is 80%).

How accurate is this versus coconutBattery, powercfg or AccuBattery?

For the live readings (charge %, charging state, time estimates) it is as accurate as your browser — those numbers come straight from the OS power driver. For battery wear/SoH it is only as accurate as the capacity figures YOU enter into the estimator, because the browser cannot read them itself.

coconutBattery (macOS/iOS), powercfg /batteryreport (Windows), upower (Linux) and AccuBattery (Android) read design and current capacity directly from the battery controller, so they are the source of truth for wear. This tool is designed to consume those exact numbers: paste your design and current full-charge capacity into the Capacity health estimator and it turns them into a PASS/FAIL verdict you can attach to a repair ticket or warranty claim. Use this page for quick live monitoring and an auditable SoH stamp; use the native tools to obtain the underlying capacity figures.

Privacy: does this tool track me, and why did browsers remove the Battery API?

This tool sends nothing to any server — all readings stay in your browser, and the optional CSV report is generated locally on your device.

The Battery Status API itself requires no permission prompt, which is precisely why browsers restricted it. Researchers showed that the combination of charge level (reported to ~1% precision) plus charging/discharging time could act as a short-lived fingerprint to correlate users across sites without consent. Because of this, Firefox removed the API entirely, Safari/WebKit never shipped it, and it is unavailable on iOS. Chrome, Edge and Opera still expose it but only in a secure context (HTTPS). If you open this page over http:// or in a privacy-hardened browser, battery access is blocked and the tool will say so honestly rather than guessing.

What is 'Time to Full Charge'?

Time to Full Charge shows the estimated time remaining until the battery reaches 100%:

- Only displayed when device is charging
- Calculated by the browser based on current charge rate
- May show 'Calculating...' when:
- Just started charging
- Charge rate is fluctuating
- System is still analyzing
- Shows 'N/A' when not charging

Factors affecting accuracy:
- Current battery level
- Charger power output
- Device power consumption during charging
- Battery age and health
- Temperature

The estimate becomes more accurate after charging for a few minutes.

What is 'Time Remaining'?

Time Remaining shows estimated battery life left before it depletes:

- Only displayed when device is discharging (not plugged in)
- Based on current power consumption
- May show 'Calculating...' when:
- Just unplugged
- Power usage is changing
- System needs more data
- Shows 'N/A' when charging

Factors affecting accuracy:
- Current battery level
- Active applications and processes
- Screen brightness
- WiFi/Bluetooth usage
- CPU/GPU load

The estimate adjusts automatically as your usage patterns change.

How is the battery history chart useful?

The battery history chart visualizes your battery level over time:

Benefits:
- See discharge rate patterns
- Identify rapid battery drain
- Compare charging speeds
- Detect battery degradation trends
- Monitor after battery optimization changes

Chart features:
- Blue dots: Normal battery readings
- Green dots: Battery readings while charging
- Smooth line: Battery level progression
- Grid: Easy percentage reference

The chart keeps the last 50 readings, updating every 10 seconds. This gives you about 8 minutes of history, useful for short-term monitoring and comparing before/after changes.

For long-term battery health tracking, check periodically over days/weeks to see if maximum battery level decreases (indicating aging).

Why does my battery show 'Calculating...'?

'Calculating...' appears when the system is still determining the estimate:

Common reasons:
- Just plugged in/unplugged (needs a few minutes)
- Power consumption is fluctuating significantly
- Battery API is gathering data
- System hasn't stabilized yet

To get accurate times:
1. Wait 2-5 minutes after plugging in or unplugging
2. Keep power usage relatively stable
3. Avoid starting intensive tasks immediately
4. Close unnecessary apps

If it persists:
- Try refreshing the page
- Check if other battery tools work
- Restart your browser
- Update your browser to the latest version

Some devices may never provide time estimates - this is normal behavior and not a tool error.

How can I improve my battery health?

Follow these best practices for better battery longevity:

Charging habits:
- Keep battery between 20-80% when possible
- Avoid frequent 0% to 100% cycles
- Don't leave plugged in at 100% overnight
- Use slow charging when not in a hurry
- Avoid charging in hot environments

Usage tips:
- Reduce screen brightness
- Close unused apps and tabs
- Disable WiFi/Bluetooth when not needed
- Use battery saver mode
- Avoid extreme temperatures (too hot or cold)

Maintenance:
- Calibrate battery every 2-3 months (0% to 100%)
- Keep software and drivers updated
- Clean device vents to prevent overheating
- Remove battery if storing device long-term (if removable)

Monitoring:
- Use this tool to track battery patterns
- Check for abnormal drain
- Monitor charging times
- Watch for sudden health drops

Remember: All batteries degrade over time - typical lifespan is 2-4 years or 300-500 charge cycles.

Key Features

• Real-time battery level monitoring
• Charging/discharging status detection
• Visual battery icon with level indicator
• Charging animation with bolt icon
• Time to full charge estimation
• Time remaining (battery life) estimation
• Honest current charge level bar (no fabricated health verdict)
• Manual Capacity Health (State-of-Health) estimator from your OS battery report
• Configurable pass threshold with PASS / MARGINAL / FAIL verdict (default 80%)
• CSV diagnostic report export with the auditable threshold and verdict
• Battery level history chart (last 50 readings)
• Real-time chart updates every 10 seconds
• Statistics: average, max, min battery levels
• Total readings counter
• Auto-refresh every 10 seconds
• Manual refresh button
• Color-coded battery states (charging, low, critical)
• Responsive design for all devices
• Dark mode support with chart adaptation
• Battery care tips and best practices
• API support detection
• 100% client-side - no data sent to servers
• No installation or registration required

Professional Battery Testing Software

For more advanced battery diagnostics and detailed hardware analysis, consider these professional tools: