Advanced Windows PowerShell Scripting Video Training

Advanced Windows PowerShell Scripting Video Training
Advanced Windows PowerShell Scripting Video Training

Wednesday, December 10, 2014

Estimating the Run Time for Various Power Options with PowerShell

For my fellow Network Administrators out there, I know you have heard this time and time again.  “Why can’t my battery last longer?”  Well first off, stop playing games.  Second, lets take a look at your Power Options.  You may have various Power Options already programmed into your laptop.   The question now is, how long will my laptop run on each plan?  The following script will only give you an estimated time in minutes that the laptop will remain on while on battery.  You have to remember that if all of the sudden you change work loads, your system will shut down sooner or last longer.  At least you will have an idea of which option will provide the longest battery life based on your laptops current work load.

To get this information, I looked at two WMI libraries; Win32_Battery and Win32_PowerPlan.  The Win32_PowerPlan allows us to collect a list of all configured PowerPlans through the property ElementName.  It also lets us know which one was originally active so we can set it back at the end of the script through the IsActive property. We can use the objects created from this WMI library to set the active power plan with the Activate method.

Win32_Battery gives us the current battery estimated lifetime in minutes through the EstimatedRunTime property.  What I have discovered through testing is that it is best to wait 3 seconds before sampling the estimated battery life. This provides a better estimated time.

Remember to unplug the laptop from external power before proceeding.

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# First detect if the laptop is on battery

 

# This will only allow the script to proceed if the laptop

# is either fully changed and not plugged in, or is

# not in danger of losing power.

$AcceptableBatteryStatus = 1,3

 

If ((Get-CimInstance -ClassName Win32_Battery).BatteryStatus -in $AcceptableBatteryStatus)

{

    # Get all PowerPlans

    $PowerPlans = Get-CimInstance -Namespace "root\CIMV2\power" -ClassName Win32_PowerPlan

 

    # Get the current PowerPlan

    $Current = $PowerPlans |

        Where-Object IsActive -eq $True

 

    # Get a list of all PowerPlans names

    $PPNames = $PowerPlans |

        Select-Object -ExpandProperty ElementName

 

    # Go through each Power Plan and set each one. Then collect

    # estimated runtime information.

   

    $Data = @() # Holds the retuned time estimates.

 

    $NumOfPlans = $PowerPlans.count

    $Count = 0

 

    $Data += ForEach ($PP in $PPNames)

    {

        $Count++

        Write-Progress -Activity "Testing Power Plans" `

                       -PercentComplete (($Count/$NumOfPlans)*100) `

                       -SecondsRemaining (($NumOfPlans+1-$Count)*3)

       

        $PowerPlans |

            Where-Object ElementName -eq $PP |

            Invoke-CimMethod -MethodName Activate |

            Out-Null

 

        # Pause for 3 seconds so the power usage can be estimated.

        Start-Sleep -Seconds 3

 

        Write-output (Get-CimInstance -ClassName CIM_Battery |

            Select-Object -Property EstimatedRunTime,

            @{N="PowerPlan";E={$PP}})

 

    }

    # Reset the origional Power Plan.

    Invoke-CimMethod -InputObject $Current -MethodName Activate | Out-Null

 

    $Data | Where EstimatedRunTime -ne $Null |

        Sort-Object -Property EstimatedRunTime -Descending

} # END: If ((Get-CimInstance -ClassName Win32_Battery).BatteryStatus -in $AcceptableBatteryStatys)

Else

{

    Write-Output "System on AC Power.  Unplug the power cable."

}

 

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