For work, I keep a Lenovo Helix (similar form factor to Surface Book) at home to be able to log in remotely due to an emergency. It's also on Windows 10. Looking in the Event Log, it has been shutdown since 11/17/15. I powered it on this morning, 1/5/16,
and it was at 93% battery after a month and a half.
Battery 1 was at 96% (tablet)
Battery 2 was at 88% (keyboard)
Total was at 93%
It has the Fast Boot enabled, Hibernate is available but I had it shut down, not hibernated.
The only Windows 10 difference I see between this and my Surface Book is that Windows 10 on the Helix doesn't give the option "On battery power, stay connected to Wi-Fi while asleep" so I assume the hardware doesn't support that option.
I don't see how staying on wi-fi when asleep would affect the battery on the Surface Book when it is shut down, but still wanted to point out the difference. However, when I disable this feature on the Surface Book, it still overly drains the battery when
shutdown anyway, so seems unrelated.
The only time I see the Surface Book not overly drain the battery is when I have the tablet undocked from the keyboard. Is the keyboard dock sucking battery from the tablet when it is shut down or hibernated?