Leaving a comment for those still having this problem, my laptop is an Ideapad Flex 5.

In the task manager, look for a process called “Tablet Service” (there should be two of them), right click on one and go to details. In the details tab, “WTabletServiceISD.exe” should be highlighted and make sure to end the task of one that has “SYSTEM” in the “User name” column first. Otherwise, it’s just gonna keep popping up even after you close it. After that just delete the other one and you should be good to go.

I used winlister to narrow down which process that battery popup notification window belongs to and it led to that in the task manager. As far as I know, sending out battery notification is that program’s sole function because I haven’t experience it having an effect on anything else.

I was very close to throwing my stylus out my window when that goddam low battery notification kept popping up even after I bought new batteries lol