Battery problems after Windows udpate on bootcamp

I allowed a Windows 10 update to run on my Bootcamp a few weeks ago.

Since then I am having battery problems:

• the battery level drops very quickly, when it is around 30% on Mac the laptop switches off without any warning, then after restarting shows 10% charge only
• After restart it also sometimes resets the clock to 1/01 so I need to reboot in Bootcamp then reboot in OSX again in order for the clock to reset automatically to the current values
• The battery on Bootcamp is equally fast to run out and it doesn't warn me before switching off the laptop.
• After sudden switch off the battery on Bootcamp shows 50% at least even though it showed 30% or 10% on Mac.

This is all very annoying and even if I am careful the laptop switched off already multiple times.

Especially after a night when the battery level drops dramatically even though the laptop is closed (and is supposed to be sleeping).

How to fix the issue?

MacBook Air 2014 with OS Catalina and WIndows 10 on Bootcamp.