C# Signature:

[DllImport("coredll.dll")]
static extern bool GetSystemPowerStatusEx(SYSTEM_POWER_STATUS_EX pStatus,
   bool fUpdate);

VB .NET Signature:

Declare Function GetSystemPowerStatusEx Lib "coredll.dll" _
   (<Out()> ByRef pStatus As SYSTEM_POWER_STATUS_EX, _
   ByVal fUpdate As Boolean) As Boolean

User-Defined Types:

SYSTEM_POWER_STATUS_EX

Notes:

pStatus must be a valid object as values will be passed back in this structure. As the pointer to the object is not changed do not use the ref/out keywords in C#.

Tips & Tricks:

Please add some!

Sample Code:

    public static byte GetBatteryLeftPercentage()
    {
        SYSTEM_POWER_STATUS_EX powerStatus = new SYSTEM_POWER_STATUS_EX();

        GetSystemPowerStatusEx( powerStatus, true);
        return powerStatus.BackupBatteryLifePercent;
    }

Complete VB.NET sample

    Private Declare Function GetSystemPowerStatusEx Lib "coredll.dll" (ByRef pStatus As SYSTEM_POWER_STATUS_EX, ByVal fUpdate As Boolean) As Boolean

    Private Structure SYSTEM_POWER_STATUS_EX
        Dim ACLineStatus As Byte
        Dim BatteryFlag As Byte
        Dim BatteryLifePercent As Byte
        Dim Reserved1 As Byte
        Dim BatteryLifeTime As Int32
        Dim BatteryFullLifeTime As Int32
        Dim Reserved2 As Byte
        Dim BatteryBackupFlag As Byte
        Dim BackupBatteryLifePercent As Byte
        Dim Reserved3 As Byte
        Dim BackupBatteryLifeTime As Int32
        Dim BackupBatteryFullLifeTime As Int32
    End Structure

    Public Function BatteryStrength() As Integer
        Dim battStatus As SYSTEM_POWER_STATUS_EX

        If GetSystemPowerStatusEx(battStatus, True) = True Then
            Return CInt(battStatus.BatteryLifePercent)
        Else
            Return 0
        End If
    End Function

Alternative Managed API:

TODO