I have a Samsung Galaxy a11 here, I'm going to show you how to add the battery percentage. Okay up here, you can see it's off now. It's on so very simple. So first thing is just gone directly into your settings. You can go ahead and swipe up on the screen like that tap on your settings and then from here you want to go ahead and go to notifications. Then you want to tap on status bar and then right down here it says, show battery percentage, okay, you can toggle it off no battery percentage, or you can turn it on.
If you have it on now anywhere you go on the phone it's going to show up, even if you lock the phone you'll see the battery percentage. Okay, pretty simple.
Source : WorldofTech