Method A: powercfg battery report

1. Open Terminal (Admin) or Command Prompt (Admin).
2. Run:

   powercfg /batteryreport /output "C:\battery.html" /duration 14

/duration 14 extends the usage history to 14 days (default is 3).
3. Open C:\battery.html in a browser.
4. Under Installed batteries, note DESIGN CAPACITY and FULL CHARGE CAPACITY.
5. Calculate health: FULL CHARGE ÷ DESIGN × 100.
6. Check CYCLE COUNT. It is empty on some devices because the firmware doesn’t report it.
7. Review Battery usage and Usage history for abnormal drain, such as large drops while the laptop was asleep.

Method B: PowerShell one-liner

Run in an elevated PowerShell:

$d = (Get-CimInstance -Namespace root\wmi -ClassName BatteryStaticData).DesignedCapacity
$f = (Get-CimInstance -Namespace root\wmi -ClassName BatteryFullChargedCapacity).FullChargedCapacity
"{0:N1}% battery health ({1} / {2} mWh)" -f (($f / $d) * 100), $f, $d

If you get an error or empty values, the manufacturer’s driver doesn’t expose these WMI classes. Use Method A instead.

Method C: Diagnose abnormal drain

1. Energy report (run it while the laptop is idle and plugged in, with your usual apps open):

   powercfg /energy /output "C:\energy.html" /duration 60

Read the Errors and Warnings sections for drivers or devices that prevent power savings.
2. Sleep study (for drain during sleep on modern standby laptops):

   powercfg /sleepstudy /output "C:\sleepstudy.html"

3. Current blockers: powercfg /requests shows which processes are preventing sleep right now.

Interpreting results

• Above 90%: healthy.
• 80–90%: normal wear.
• Below 80%: noticeable loss of runtime. Consider replacement if autonomy is a problem.
• Below 60%, or a swollen chassis or trackpad: stop using it on battery and replace it. Swelling is a safety issue.

Verification

Re-run Method A after a few weeks. A rapid drop in Full Charge Capacity suggests a failing cell, not normal ageing.

Notes

• Percentages can vary by 1–3% between runs.
• Heat accelerates wear. Avoid leaving the laptop at 100% on the charger in hot environments if your vendor utility offers a charge limit (80% mode).