iPhone 11 Pro Max Strange Drain

[Fustnd1]

Hello, I have problem with my phone. So my phone is still on iOS 13.3.1, but I noticed unusual drain when my phone has 20-50%. Actually, it looks that my phone may drop 2% of battery in one moment. For example: I used my phone 20 minutes, my phone had 30% battery. I locked phone, and after 30secs I turned it on. I noticed that phone has 28%, situations like this happens really often. What should I do? It's everything fine, or should I send my 11pro max to Apple?

 

[ruslan120]

Attempt at helpful: What does battery health say?

Conspiracy Theory: It’s normal - Apple does this every year with old iPhones to make you buy the new one. They also get slower

 

[Fustnd1]

Attempt at helpful: What does battery health say?

Conspiracy Theory: It’s normal - Apple does this every year with old iPhones to make you buy the new one. They also get slower

So, this situation has been happening since March 2020, and in those days my 11 pro max was the newest device. I have still ios 13.3.1 on them, so it isn't the newest iOS, iphone 11 series started from ios 13. Before my phone had 100%, now it has 98% battery health and it still happens.