I went on a recent vacation with my Surface Laptop 3 and was shocked to learn that the computer was losing battery life overnight after I had shut it down.
A Laptop that loses battery life while off is the least useful thing ever. I woke up having gone from 70% battery life to 0.
There is a bunch written about this on the Internet. My solution was to disable fast startup.
Bring up Windows Settings and select System,, and then power and sleep.
Select the "Additional Power Settings" link on the right side of the window.
Click "Choose what the power button does" from the left menu.
Then click the "Change Settings that are Currently Available" link.
Under shut down settings, be sure that Turn on Fast Startup (recommended) is unchecked.
Save your changes and you should be good to go.
I believe this fast startup is keeping the computer active in some manner which is depleting battery life.
I did a lot of reading before finding a solution that worked and didn't require me to go into the registry.
Hopefully this works for you too.