Battery drain during Picture update

Dear all,
with my first watch face for the F3 I have a big problem.

The idea of the watch face is, depending of the battery value the eyes will change the color.
For this I separated the picture into three slices, where two slices won't be changed and their position is defined in the "layout.xml".

The third picture is set in the [FONT=Courier New]onUpdate(dc)[/FONT] function after [FONT=Courier New]View.onUpdate(dc);[/FONT]

Following code is used.

var SystemStats = Sys.getSystemStats();
var batteryLevel = SystemStats.battery;

if (batteryLevel <= batteryLevelAlarm)
{
dc.drawBitmap(0, 80, FaceEyes_red);
}
else if (batteryLevel <= batteryLevelWarning)
{
dc.drawBitmap(0, 80, FaceEyes_yellow);
}
else
{
dc.drawBitmap(0, 80, FaceEyes_normal);
}


During the battery level was greater than 40% everything was OK, but after reaching 40 % the battery drains down to 7 % within one day.

FW of F3 was updated to version 6.80 today.

Does anybody know this problem? Are there any ideas to solve it?

Thanks and regards,
Roland