iphone XS Max battery running out quickly after iOS 14.4 software upgrade

Hello,

There is some chatter about that. However, with a new version of iOS, there is always additional processing for re-indexing etc.

Listed below are the standard steps for short battery life:

1) Have you tried a restart?  If not, do it now.

2) Go to Settings > Battery > BATTERY USAGE BY APP to see the apps that are consuming your battery.

3) Check “Battery Health” in the link: 

iPhone Battery and Performance

4) If all else fails, consider a battery replacement:

iPhone Battery & Power Repair

Good luck.

The update had nothing to do with your issue.

What is the battery health?