Find out what’s draining your battery
To identify which apps are sucking up the most power, and which you should close when not in use, visit Settings > General > Usage > Battery Usage. You can then decide whether to use the apps less, or delete them.
Manage background app refresh
If you don’t need an app updating in the background, go to Settings > General > Background App Refresh and switch off the refresh options.
Remove cases when charging
Charging your device when it’s inside certain styles of cases may generate excess heat, which can affect battery capacity. If you notice that your device gets hot when you charge it, take it out of its case first.
Keep your phone away from extreme temperatures
Your device is designed to perform well in a wide range of temperatures, with 16° to 22°C as the ideal comfort zone. It’s especially important to avoid exposing your device to temperatures higher than 35° C, which can permanently damage battery capacity. Charging or storing the device in high temperatures can damage it further. Even storing a battery in a hot environment can damage it irreversibly.
Check emails manually and save power by turning off the fetch function. You can also fetch data manually, or set fetch data to “hourly.”
To turn off the feature, go to Settings > Mail, Contacts, Calendars > Fetch New Data.
Turn cellular data and 3G off when they’re not needed
Go to Settings > General > Cellular > Switch Cellular Data and Enable 3G to Off
Switch to airplane mode
When no coverage exists, switch to airplane mode. Your iPhone always tries to search for coverage, even in places where no coverage exists, which uses battery power.
Let your phone complete at least one charge cycle each month
A charge cycle is when you charge the phone to 100% and let the battery power drain completely, after which you charge it again. Going through a charge cycle per month keeps the electrons in the iPhone lithium battery
Dim the light
To keep energy output to a minimum, go to Settings > Display & Brightness, turn Auto-Brightness off, and drag Brightness as low as is comfortable.
Turn off push notifications
Push notifications rely on battery, so if you don’t need them, turn them off. Go to Settings > Notification Center > and turn Show on Lock Screen, or even Allow Notifications, to off.
Minimise the motion
Animating transitions and blurring backgrounds has become more efficient, and is certainly visually fun. If you don’t need effects such as transitions, you can turn them off and save a small amount of processing. Go to Settings > General > Accessibility > Reduce Motion, and turn it on.