Check battery usage on iPhone and iPad
Identify where all your mobile energy is going
You’re probably already aware that iOS works differently to the Mac with power management. Apps can’t just run in the background eating up battery power — if they’re not visible on screen, they operate in limited ways in the background. This means you don’t have to worry about quitting all apps to save battery life in quite the same way — but some apps still hog energy more than others, and you’ll want to identify them.
In Settings, tap the Battery option (in the third group down). The Battery Usage section will tell you exactly which apps are responsible for running down your charge. Apps are listed in descending order of culpability, showing what percentage of your total power expenditure each is responsible for; you can also tap the clock icon to see how long apps have spent on the screen, and how much time they’ve been working in the background. Usefully, rows may also list ways in which apps might be using your battery even when not visible. Mostly, reasons will be obvious — a podcast app will indicate that it plays audio, say. It’s the nebulous “Background Activity” to watch for.
This will generally consist of two things: fetching data in the background; and checking your location. If you see apps you don’t really use, but are performing a lot of background activity, consider uninstalling them. Just two apps can add up to 5% of usage, which could mean another hour of charge.