Users found that the system update caused the iPhone to discharge quickly even with the screen turned off. This is relevant for iOS 13.5.1.
As journalists write, the problem is not observed on all smartphones that have received the update. The experts explained that you need to check if your iPhone has been damaged. First, you should check the temperature of the device in standby mode (it may be enough just to touch). In some cases, it is noticeably higher than room temperature. Secondly, you need to go to the Settings menu, select the Battery item and see the activity in the state when the screen is off. If it says more than 60 minutes, then there is a problem. You can also check the activity of individual applications.
It is not yet clear how to solve the problem, notes NIX Solutions. You can try uninstalling the apps that are using the most power, or limiting background updates. There is a chance that Apple will fix the issue with an iOS 13.6 update.