After testing, and running my iPhone’s battery flat, I’ve come up with the following ways of making your iPhone battery last all day. And the nice thing is that these methods are quick and simple, and don’t involve making drastic changes to iOS.
The first one, but also the most effective, and that is to switch on Low Power Mode.
As the name suggests, activating this setting puts your device into low power mode. And it really does work, giving you about three hours of extra battery life. If you are worried about your battery not making it through the day, this is the setting to activate.