Can't turn off baterry saver

Hi 

I can't turn off battery saver. There is not any option on the phone that can turn it off or generally that's called battery saver. It only appears as a notification when my battery is lower than 15% and it says "turn on battery saver" (even when it's already on) and I can't find it anywhere else on the phone. I haven't noticed that it affects my phone much but it decreases screen brightness significantly and that bothers me a lot. It happend to me once before and I had to factory reset my phone because I just couldn't turn it off any other way, and now I turned it on again by accident. I would really appreacite it if someone could help me, I really don't want to factory reset my phone again.