JanDeDobbeleer/oh-my-posh · error

unknown value received

Error message

unknown value received

What it means

On Windows, systemGetAll calls Win32 GetSystemPowerStatus. When BatteryLifePercent is 0xFF (255) the OS is saying the percentage is unknown (e.g. no battery or transient state), so the library errors with 'unknown value received'.

Source

Thrown at src/runtime/battery/battery_windows.go:75

var getSystemPowerStatus = kernel32.NewProc("GetSystemPowerStatus")

func systemGetAll() ([]*battery, error) {
	var sps systemPowerStatus

	r1, _, errno := syscall.SyscallN(getSystemPowerStatus.Addr(), uintptr(unsafe.Pointer(&sps)))
	if r1 == 0 {
		if errno != 0 {
			return nil, error(errno)
		}
		return nil, syscall.EINVAL
	}

	if sps.BatteryFlag&batteryFlagNoBattery != 0 || sps.BatteryFlag == batteryFlagUnknown {
		return nil, &NoBatteryError{}
	}

	if sps.BatteryLifePercent == batteryLifePercentUnknown {
		return nil, errors.New("unknown value received")
	}

	b := &battery{Full: 100, Current: float64(min(sps.BatteryLifePercent, 100))}

	switch {
	case sps.BatteryFlag&batteryFlagCharging != 0:
		b.State = Charging
	case sps.BatteryLifePercent == 100 && sps.ACLineStatus == acLineOnline:
		b.State = Full
	case sps.ACLineStatus == acLineOnline:
		b.State = NotCharging
	case sps.BatteryFlag&batteryFlagCritical != 0:
		b.State = Empty
	default:
		b.State = Discharging
	}

	return []*battery{b}, nil

View on GitHub (pinned to 0976794618)

Solutions

1. Confirm a real battery exists (powercfg /batteryreport or Get-WmiObject Win32_Battery); if none, expect NoBatteryError instead
2. Retry after a moment - the value can be transiently unknown after resume/suspend
3. Update BIOS/battery drivers so Windows can report the percentage
4. Handle the error gracefully and hide the battery segment

Example fix

null

$sps = [System.Windows.Forms.SystemInformation]::PowerStatus
if ($sps.BatteryLifePercent -eq 255) { 'percentage unknown - segment will error' }

bat, err := battery.Get()
if err != nil {
  log.Printf("battery percentage unknown: %v", err)
  return nil // hide battery segment
}

When it happens

Trigger: battery.Get()/systemGetAll on Windows when SYSTEM_POWER_STATUS.BatteryLifePercent == 255 (batteryFlag passed the no-battery checks but percent is still unknown).

Common situations: Desktops/VMs with a marginal battery detection race; UPS devices where Windows reports unknown percent; some laptops right after resume or with failing battery firmware; Hyper-V guests.

Related errors

• unable to add font resource using AddFontResourceW
• unable to open window process
• no matching window title found
• unable to delete font file after registry key open error
• unable to open HKEY_CURRENT_USER

AI-assisted analysis of JanDeDobbeleer/oh-my-posh@0976794618 (2026-08-31). Data as JSON: /api/errors/a98ba27c8053f0ae. Report an issue: GitHub.