TestLap
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Online laptop battery check

Read the battery state, measure real-world drain, and check battery wear with a single Windows command.

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Reading…

Time remaining

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Full in

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Measure battery drain

Unplug the charger, click start, use the laptop normally for 10–15 minutes and come back.

Elapsed

0:00

Drained

0%

Estimated / hour

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Check battery wear with Battery Report (Windows, 30 seconds)

Fastest way: press Win + R, paste the command below and press Enter. The battery report opens in your browser.

Click the command box or the Copy button.

Did not work? See the step-by-step cmd method
  1. Press Win + R, type cmd, press Enter.
  2. Paste this command and press Enter:powercfg /batteryreport /output "%USERPROFILE%\Desktop\pin.html"
  3. Open pin.html on your Desktop and find Installed batteries:
  • DESIGN CAPACITY: capacity when the battery was new.
  • FULL CHARGE CAPACITY: capacity today.
  • CYCLE COUNT: charge cycles. Under 300 is low, over 800 is high.

Runs entirely in your browser. No data, images or audio are ever uploaded.

How to test in 3 steps

  1. 1

    Read the battery panel

    The page shows charge level, charging state and time remaining as soon as it loads (Chrome and Edge).

  2. 2

    Unplug and click "Start measuring"

    Use the laptop normally for 10–15 minutes, browsing or watching video. The page records how fast the battery drains.

  3. 3

    Run Battery Report for wear

    Browsers cannot read battery wear. Follow the one-command guide below; it takes 30 seconds.

Reading the results

  • Wear under 20%, drain under 20% per hour while browsing: good battery for a used laptop.
  • Wear 20–40%: weak battery, 2–3 hours of use. Use it to negotiate.
  • Wear above 40% or drain above 30% per hour: add the cost of a new battery to the price.
  • The percentage jumps (for example 60% to 20% within minutes): a failing cell, the battery is close to dead.
  • "Not charging" at 55–80% while plugged in: many brands stop charging at a threshold to protect the battery; it is not a fault. Check the vendor app such as Lenovo Vantage, MyASUS or Dell Power Manager.

Battery tips when buying used

  • Stay unplugged while running the other tests such as the screen test and the speaker test; watching the battery during real use is the most honest measurement.
  • Ask whether the battery is original. The Battery Report lists MANUFACTURER and SERIAL NUMBER; replacement batteries often show an unknown brand or blank fields.
  • A battery with less than 20% wear in the report is the mark of a lightly used machine and saves you a replacement after purchase.

Frequently asked questions

The page says my browser cannot read the battery+

Firefox and Safari removed the Battery API for privacy reasons. Open the page in Chrome, Edge, Opera or Brave. If that is not possible, use the Battery Report guide below.

How much battery wear is acceptable?+

Under 20% is good for a used laptop. 20–35% is usable and worth negotiating over. Above 40% the battery is clearly weak, lasting only 1–2 hours, so budget for a replacement.

What drain rate per hour is normal?+

Web browsing at medium brightness: 10–20% per hour for an office laptop. More than 30% per hour means a worn battery or something consuming power in the background; check Task Manager.

It shows 100% but the laptop dies when unplugged+

The battery is completely dead and only the gauge chip is reporting. Test by unplugging while the laptop is running. On a used machine this means an immediate battery replacement.

How do I spot a swollen battery?+

The touchpad is pushed up, the bottom cover bulges, or the laptop rocks on a flat table. A swollen battery is a fire risk: do not buy it and do not keep using it.