Battery Test

What This Test Shows

This test reads your device's battery level and charging status directly from the browser using the Battery Status API. It's a quick reference — it shows current charge level and whether you're plugged in, but it cannot report battery health or maximum capacity. For that, your operating system has dedicated tools, and we explain how to access them below.

How to Check Battery Health Properly

1. Windows: Open Command Prompt and type powercfg /batteryreport then press Enter. A report file is saved — open it to see full charge capacity versus original design capacity, cycle count, and usage history.
2. macOS: System Settings → Battery → Battery Health. Click the information (i) button to see your cycle count.
3. iPhone: Settings → Battery → Battery Health & Charging. Shows capacity as a percentage of original.
4. Android: Settings → Battery → Battery Health (path varies by manufacturer and Android version).
5. On Windows, the battery report also shows recent charge and discharge sessions, which helps identify charging problems.

What Your Results Mean

Charge level shows correctly and updates: The Battery Status API is working and your device is reporting live data.

Status shows "Charging": Your device recognises the charger and is actively charging.

Status shows "Discharging": You're running on battery. The level should decrease over time.

Level appears stuck and doesn't update: Some browsers update this value on a delay. Refresh the page after a minute to see a change.

Data is blank or "API not available": Your browser doesn't support the Battery Status API — Firefox removed it for privacy reasons. Try Chrome or Edge for a reading.

Windows battery report shows capacity well below design capacity: Your battery has degraded. Below 80% of original capacity is where most devices start showing noticeably reduced runtime.

Common Problems and Fixes

Battery draining much faster than before

Run the OS battery health check. If full charge capacity is well below design capacity, the battery has worn down. Replacement is the solution — capacity doesn't increase with software changes.

Device discharges even when plugged in under heavy use

The charger isn't supplying enough wattage for the current power draw. Intensive tasks on a low-wattage charger cause net discharge even while connected. Use the charger that came with the device or one rated at the same or higher wattage.

Battery percentage jumps or drops suddenly

The battery needs recalibration. Run it all the way down to 0% — device shuts off from low battery — then charge to 100% in one uninterrupted session. This allows the system to relearn the true capacity range.

Device shuts off at 15–20% rather than near 0%

A common sign of significant battery degradation. The battery's internal voltage drops below the safe threshold earlier than the percentage suggests. Replacement is the solution.

Charging much slower than before with the same charger

Check the cable. Charging cables degrade internally from repeated bending, especially near the plug and the device connector. Try a known-good cable from the same manufacturer.

Why This Test Matters

The most important use of battery monitoring is catching early degradation. Reduced runtime, inaccurate percentage reporting, and a device that charges to 100% but dies within an hour are all signs of worn capacity.

Knowing where your battery stands helps you decide whether replacement is worthwhile before buying a new device. A battery replacement on a laptop that otherwise works well is significantly cheaper than a new machine.

Why Batteries Degrade and Drain Fast

Two different things get blamed on "a bad battery": fast draining, and genuine capacity loss. They have different causes.

Capacity loss is normal ageing. Lithium-ion batteries wear with every charge cycle and lose capacity faster when kept hot or constantly charged to 100%, which is why a two-year-old laptop holds noticeably less than when new. Fast draining, on the other hand, is usually software: brightness at maximum, dozens of background apps, and aggressive sync or location services burn through a healthy battery quickly. Heat accelerates both problems, so a laptop that lives on a soft surface or runs hot ages faster. Telling the two apart matters — a draining problem is fixable with settings, while real capacity loss eventually needs a new battery.

How to Check True Battery Health

The browser can read your current charge level but not your battery's full health, so for the real numbers go to the operating system. On Windows 11 24H2, open Terminal or Command Prompt, run powercfg /batteryreport, and open the HTML file it creates — it shows "Design Capacity" versus "Full Charge Capacity," and the gap between them is your wear. On macOS Sequoia, go to System Settings → Battery → Battery Health to see the condition and maximum capacity percentage. A battery at 80% of its design capacity or below is well into its wear life; under roughly 50–60%, replacement is usually worthwhile.

How to Extend Your Battery's Lifespan

1. Keep charge between 20% and 80%. Avoiding full charges and deep discharges is the single best habit for longevity.
2. Don't let it cook. Heat is the main enemy — use a hard surface for airflow and avoid leaving it in hot cars or direct sun.
3. Use battery-saver and lower brightness. The screen is the biggest drain; dimming it and enabling the saver mode stretches each charge.
4. Trim background apps. Close sync clients and unused apps that quietly run and drain power.
5. Enable optimised charging. Both Windows and macOS can learn your routine and hold off on the final charge to reduce wear.
6. Check health periodically. Run the OS battery report every few months so a declining battery is no surprise.

Signs Your Battery Needs Replacing

A few clear signals separate a battery that's genuinely worn out from one that just needs better habits. Runtime has collapsed — a charge that once lasted hours now drains in a fraction of the time under light use. The health reading is low, with full-charge capacity well under 60–70% of the original design capacity in a Windows battery report or macOS Battery Health. The percentage jumps or drops suddenly, say from 40% straight to shutdown, because a worn cell can no longer report charge accurately. And most seriously, any physical swelling — a trackpad that no longer sits flat or a bulging back panel — means stop using the device and replace the battery promptly, as a swollen lithium-ion cell is a safety hazard. Short of swelling, a worn battery is just an inconvenience, and a replacement revives a laptop that's otherwise perfectly good.

Frequently Asked Questions