I have a Samsung Galaxy a71 here, I'm going to show you how to add the battery percentage on the status bar. Okay, very, very simple, so first thing is: go ahead! Go into your settings! You can just swipe up on the screen like that, find your settings icon right there and then from here. We want to go ahead, and we want to scroll down third one down as notifications tap on notifications. Then you want to tap on status bar, and then it's right here show battery percentage. You can turn it off, or we can toggle it back on right there and then, once it's on doesn't matter where you are on the screen. It's going to show up on the top left-hand side on the status bar.
So pretty simple.
Source : WorldofTech