The problem may be some hardware drawing power when the laptop is powered down. Common bits of hardware that do this are USB mice and keyboards and in-built wireless network cards.
A few things to check:
1) When powered down, is the mouse still active (light on)?
2) Open Device Manager
* For each hardware listed, open Properties
* Is there a `Power Management` tab?
* If yes, ensure `Allow this device to wake the computer` is NOT selected
* Click Ok (and move onto next hardware entry)
For the 2nd step, there will likely be dozens of hardware entries in Device Manager. Each check takes about 15s, so you'll need to budget about 5 or more minutes...be patient!
Another problem may be the network card itself. By default, modern network cards continue to draw power even when the laptop is "off". Refer to this Superuser question and answer for details.
In Windows 10, you can list devices that can wake the computer (and will therefore draw current) as follows:
* Run a command prompt (with administrative privileges)
* Type "powercfg -devicequery wake_armed" and hit <Enter>
The response should be
NONE. If not, find these devices in Device Manager and ensure
Allow this device to wake the computer is off.