Why do I have battery drain when my Surface Pro 4 shuts off?

[borgeindergaard]

Start the registry editor (regedit.exe).
Move to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Power.
Double-click CsEnabled and set to 0, then click OK

That disables Connected Standby and forces the computer to use regular Sleep.
To disable Fast Startup (like he asked for) you go to Power Options > Choose what the power buttons do > Enable Administrator rights > Remove the check mark on "Turn on fast startup (recommended)"

 

[twentefan]

I have changed the setting and will monitor how the battery drain evolves.
Of course it is ridicilous we have to do this and MS doesn't offer a decent fix for an expensive device as this.