A bluetooth mouse (even when disconnected, but just because it is configured) can wake a PC from sleep mode causing battery drainage.
Issue the following CLI commands for diagnostics and resolution:
powercfg -devicequery wake_armed
(find the device name that will wake the system)
powercfg -devicedisablewake "complete devicename above"
This should return the sleep mode to a nice long battery life.
Here's the background about how I discovered this.
Recently I began noticing that it wouldn't make it overnight in sleep mode without draining the battery. It would be fully charged at 10pm when I put it to sleep and at 7:30am I'd open it up and find it at 6% and in hibernate mode.
A little searching I came across an forum post somewhere and the author described a recent use of a bluetooth mouse and the short battery life began. It dawned on my that I also had recently used a bluetooth mouse.
Looking a power settings I found the HID mouse was set to wake the computer from sleep mode. Using the commands above I disabled wake capability for the HID mouse and everything returned to normal.