Some malicious programs might force the CPU to work indefinitely until it burns out. And it's at this point that overheating and battery draining problems arise. To figure out which of your applications is misbehaving up, look at your iPhone 7 Plus's battery use and see which app consumes the most power. This is how you get to this menu:

1. From the Home screen, choose Settings.
2. The battery should be tapped.
3. Wait for the Battery Usage information to appear.
4. Show Detailed Usage by tapping the button. This will reveal a breakdown of front and background power use.
5. Tap the Last 7 Days tab to receive a more comprehensive picture of power use over time.
6. The battery used in iOS 12 may be examined in the Settings->Battery->Show Activity menu. Tap Battery Use to get usage data in percentages. Tap Last 10 Days to see your iPhone's power use over time.
7. If you see any apps using unusual amounts of power, they are most likely glitching and are one of the causes of your phone's battery depleting quickly. In such a scenario, you'll have to deal with the rogue program.