Battery Drains While Shutdown

the problem is the latest firmware of SP4 of Aug 2019. before this upgrade all works fine!!!!!

But I don't think it's possible to go back to the old version? It's totally ridiculous that Microsoft still haven't fixed this. What can we do but never buy Microsoft hardware again?

Reported issues existed well before August 2019- My battery drain always existed but took a little while before I realized what was going on.  My issue goes back to 2016.

I've watched this thread for a long time, since my Surface Pro 4 exhibited this problem.  I've followed it because operating on battery power is important to my application.  Because the problem has been attributed to so many differentupdates and users report so much variation in the amount of drain and because of my own experience and from what I've read on other threads, I believe many of the problems reported here are the result of aging batteries.   

My experience: I first noticed the problem when I was losing about 5 percent of design battery capacity over night.  That got steadily worse until I could not count on my battery at all.  Not long after that it failed altogether.  It shut down the instant power was disconnected.   Diagnostic showed a failed battery.  I gave it back to Microsoft for a $300 credit on a Surface Pro 6 on which I  keep battery limiter enabled whenever I am using in on the power supply.

Other threads: Enterprise IT administrators who manage large numbers of Surface Pros have reported that the batteries typically fail after four to six years unless the machine is left connected to AC power for extended periods. 

Microsoft might have implemented the battery limiting function in firmware to enable users to get more life out of their Surface batteries.

Unfortunately it's not possible to rollback to an old firmware... 

My next hardware will not be Microsoft. Sorry!