I have been able to reproduce this problem with a new Dell Venue 8 Pro and a Plugable 3000 USB 3.0 docking station. Before installing the Displaylink drivers, connected standby would drain less than 1% of the battery per hour. After I installed the drivers, the Intel GPU would never go to sleep, so battery drain would be over 6% per hour while in sleep mode, basically losing half of the battery during the night, while the tablet sleeps.
Running "powercfg.exe /sleepstudy" shows the Intel GPU always running at 100%, while the rest of the system reaches a low power state.
After uninstalling the Displaylink drivers, the problem disappears. The Intel GPU disappears from the report, and battery drain again becomes normal.
It is very easy to reproduce.
I was on Windows 8.1 32-bit with the latest Displaylink drivers (7.4M2), automatically installed by Windows and verified against the downloadable version number. I haven't had any other Displaylink driver on my system before that. The tablet is two weeks old.
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