Как узнать заряженность батарей?

Code:

procedure TForm1.Button1Click(Sender: TObject);

var

SysPowerStatus: TSystemPowerStatus;

begin

GetSystemPowerStatus(SysPowerStatus);

if Boolean(SysPowerStatus.ACLineStatus) then

begin

   ShowMessage('System running on AC.');

end

else

begin

   ShowMessage('System running on battery.');

   ShowMessage(Format('Battery power left: %d percent.', [SysPowerStatus.BatteryLifePercent]));

end;

end;