The iPhone has two power modes – normal and Low Power Mode. As the battery level of the iPhone falls throughout the day it may be in danger of running out of juice before you can get to a charger. Thankfully, you can enable Low Power Mode to extend the battery life, giving you an extra hour or two of running time. Enable Low Power Mode by going to Settings>Battery or add a button to Control Centre. The only problem is that you may not notice the battery expiring and cannot see it if the iPhone is in your pocket. A better way to enable it is to automate it with Shortcuts. Just choose the level at which it should be activated and it will automatically turn on.
Step-by-step Automate Low Power Mode on an iPhone