3 Disable Background App Refresh
Background App Refresh is a convenience feature. It allows certain apps to stay current by updating when they’re not actively open. It’s handy, but it can be a huge battery (or data) drain, depending on the type or number of apps that are using it.
Even if you want some apps to continue refreshing in the background, it’s smart to look over your Background App Refresh preferences and weed through which apps really need that feature. Just go to Settings > General > Background App Refresh. If you want to maximize battery life, be selective about which apps you choose.