Laptop Battery Test

This laptop battery test shows your battery level, whether it is charging and the time the system expects it to last, then measures the real drain rate by recording every change in the level while you use the laptop. You can add a light or heavy processor load to see how fast the battery drains when you work hard, and the session is saved in your browser, so a shutdown at 0% does not lose it. The health calculator works out wear from design and full charge capacity and reads the battery report Windows creates. Live readings work in Chrome, Edge and Opera on Windows, ChromeOS, Linux, Mac and Android. The calculator works in any browser.

How to test a laptop battery

1. Charge the laptop to at least 50%, then unplug the charger.
2. Set the screen brightness and apps the way you normally use them. Brightness changes the result more than anything else.
3. Choose a load: None for normal use, Light for steady office work, Heavy to load every processor core.
4. Press Start measuring and keep using the laptop, or leave it on this page with Keep the screen on switched on.
5. After the level has dropped by 2% or more, read Drain rate and Time left. Longer sessions give more accurate numbers.
6. To compare with the battery's original runtime, enter the capacities from your battery report in the health calculator.

What the readings mean

Light browsing on a thin laptop in good health often uses 8 to 15% an hour, video calls more, and games or a heavy load 40% or more. A level that drops several percent at once, or a laptop that shuts down at 10 to 20%, points to a worn battery whose capacity readings are out of step with its real charge.

How to check battery health on Windows

Windows keeps a full history of your battery, and one command turns it into a report.

1. Press the Windows key, type cmd and open Command Prompt (Terminal works too).
2. Type powercfg /batteryreport and press Enter.
3. Windows saves battery-report.html and shows where, usually in your user folder such as C:\Users\YourName.
4. Open that file with Open battery report on this page, or open it in your browser and read the Installed batteries section.
5. Compare Full charge capacity with Design capacity. Full charge capacity divided by design capacity is the battery's health.

The report also lists Cycle count, a Battery capacity history that shows how the capacity has fallen week by week, and Battery life estimates comparing runtime now with runtime when new. The health calculator draws the capacity history as a chart when you open the file. Some laptops report a cycle count of zero or leave it blank, which means the battery does not share it.

How to check battery health on a Mac

1. Open the Apple menu, then System Settings, then Battery.
2. Click the info button next to Battery Health. You see the condition, either Normal or Service Recommended, and on Macs with Apple silicon the Maximum Capacity as a percentage.
3. For the cycle count, hold the Option key, open the Apple menu and choose System Information. Select Power in the sidebar and read Cycle Count under Battery Information.

Apple rates most MacBook Air and MacBook Pro batteries for 1,000 cycles. You can paste the Power section into the calculator above, and it reads the cycle count and maximum capacity.

iPhone and Android battery health

iPhone: open Settings, then Battery, then Battery Health (Battery Health & Charging on iPhone 14 and earlier) for Maximum Capacity. On iPhone 15 models and later, the same screen also shows the cycle count. Apple designs the iPhone 15 and later to keep 80% of their capacity at 1,000 full cycles, and earlier models at 500.

Android: on Pixel 8a and later, open Settings, then Battery, then Battery health. On Samsung Galaxy phones, open the Samsung Members app, tap Support, then Phone diagnostics, then Battery status. To check how fast a phone charges, use the charging speed test, and if it will not charge at all, see phone not charging.

The battery drains fast

Work through these in order, measuring again after each change:

• Screen brightness and refresh rate. Lower the brightness, and on laptops with 120 Hz or faster screens, try 60 Hz on battery.
• Background apps. On Windows 11, open Settings, then System, then Power & battery, then Battery usage to see what used the most. On a Mac, check Activity Monitor's Energy tab.
• Power mode. On battery, set Windows to Balanced or Best power efficiency, and use Low Power Mode on a Mac.
• The graphics card. On gaming laptops, a game launcher or browser running on the separate graphics card can double the drain. Close it or set the app to power saving in Windows graphics settings.
• A worn battery. If the health calculator shows under 80%, the battery holds less charge and every hour costs a bigger share of it.

Heat speeds up battery wear too. If the laptop runs hot even when idle, follow the laptop overheating fix steps.

The laptop says plugged in, not charging

This message is often normal. Many laptops stop charging at 80% or less to protect the battery when a battery care mode is on, such as Conservation Mode in Lenovo Vantage or Battery Health Manager on HP. If you need a full charge, turn that mode off. If the battery stays at a low level, check that the charger matches the laptop's wattage (USB-C phone chargers are often too weak), try another outlet, update the BIOS, and check whether the battery health is very low.

When to replace the battery

Replace the battery when its health is under about 70%, when the laptop shuts down well before 0%, or when the runtime no longer gets you through your day. Stop using the laptop straight away if the battery swells: a raised touchpad, a lifting keyboard or a case that no longer closes flat are the signs. Take it to the maker or a repair shop, because a swollen lithium battery can catch fire if it is punctured.

What a browser can and cannot read

Websites can read the charge level, the charging state and the system's time estimates, and only in Chromium browsers such as Chrome, Edge and Opera. They cannot read capacity, health, cycle count, voltage or temperature, which is why the health calculator uses the numbers from your battery report. The drain rate on this page is measured from whole percent steps, so it gets more accurate the longer you measure. To see how a heavy load drains the battery, run the cpu stress test or the gpu test while a session is measuring here.

Laptop battery test questions