# Reading powercfg /batteryreport: capacity, cycles and real wear

> How to read design capacity versus full charge capacity, spot a dying battery, and tell wear apart from a calibration problem.

**Tested on**

- Build: 26300.9457
- Edition: Pro (26H2)
- Architecture: x64
- Evidence: E1
- Verified: 2026-10-29

## The short answer

`powercfg /batteryreport` writes an HTML file with the battery's history. Three numbers matter:

- **Design capacity** — what the battery was built to hold.
- **Full charge capacity** — what it holds now, when "full".
- **Cycle count** — how many charge cycles it has been through.

Wear = `1 − full charge / design`. Under ~20% wear is normal for a used machine; over ~30% means the runtime you see is the runtime you get.

## Generate and read it

```powershell
powercfg /batteryreport /output "$env:TEMP\battery.html"
Start-Process "$env:TEMP\battery.html"
```

The report contains:

| Section | What to read |
|---|---|
| Installed batteries | design capacity, full charge capacity, cycle count |
| Recent usage | power state transitions, battery percentage |
| Battery usage | drain per session |
| Usage history | how the machine was used over weeks |
| Battery capacity history | **full charge capacity over time** — the wear trend |
| Battery life estimates | projected runtime at current drain |

The **capacity history** table is the honest one: a single reading can be off, a downward trend over months cannot.

## Capacity vs calibration

Two different things get called "the battery is dying":

- **Real wear** — full charge capacity has genuinely dropped. Nothing fixes it but a new cell.
- **Calibration drift** — the fuel gauge's estimate is wrong; the battery may shut down at 20% or report 100% for an hour.

Calibration is worth trying once: charge to 100%, discharge to shutdown, charge fully again. If the reported capacity then jumps, it was the gauge, not the cell.

> **Caution: Do not run a full discharge on a laptop you need tomorrow**
>
> A calibration cycle takes hours and leaves you without a machine. Do it when you can afford the downtime, and never on a battery that is already swelling.

## Interpret the numbers

| Observation | Meaning |
|---|---|
| Full charge ≈ design, high cycles | healthy cell, normal ageing |
| Full charge far below design, low cycles | defective cell or heat damage |
| Capacity drops then recovers after calibration | gauge drift |
| Runtime collapses but capacity looks fine | high drain, not wear — check [standby](https://winbook.fyi/en/hardware/laptop/modern-standby/) and throttling |
| Battery not detected at all | connector, firmware, or a dead pack |

```powershell
# quick alternative when the HTML is overkill
Get-CimInstance -Namespace root\wmi -ClassName BatteryStaticData |
  Select-Object DesignedCapacity,DeviceName,ManufactureName,SerialNumber
Get-CimInstance -Namespace root\wmi -ClassName BatteryFullChargedCapacity |
  Select-Object FullChargedCapacity
```

`DesignedCapacity` and `FullChargedCapacity` are in mWh; the ratio is your wear figure. Not all firmware exposes them.

## Battery care that actually matters

- **Heat** ages cells faster than cycling does. A laptop on a bed or in a bag runs hot.
- **Staying at 100%** for months is worse than cycling between 40–80%, if the firmware offers a charge limit.
- **Deep discharges** to 0% are not "good for the battery" on modern lithium packs.
- **Fast charging** is fine; heat during fast charging is what hurts.

## Related

- [Modern Standby](https://winbook.fyi/en/hardware/laptop/modern-standby/)
- [Throttling: thermal or power](https://winbook.fyi/en/hardware/laptop/throttling/)
- [Power plans](https://winbook.fyi/en/hardware/laptop/power-plans/)

## Lab boundary

E1. The report format and fields are Microsoft-documented. The lab's virtual machines expose no battery, so no capacity or wear numbers are published.

## Sources

- [Microsoft Learn — Powercfg command-line options](https://learn.microsoft.com/en-us/windows-hardware/design/device-experiences/powercfg-command-line-options)
- [Microsoft Learn — System power states](https://learn.microsoft.com/en-us/windows/win32/power/system-power-states)

---

Source: https://winbook.fyi/en/hardware/laptop/battery-report/