iPhone has an internal, lithium-ion rechargeable battery. 

WARNING: For important safety information about the battery and charging iPhone, you should lookup the Important safety information.

Charge the battery. Connect iPhone to a power outlet using the included cable and USB power adapter.

iPhone connected to the power adapter

Note: Connecting iPhone to a power outlet can start an iCloud backup or wireless iTunes syncing. 

You can also charge the battery by connecting iPhone to your computer, which also allows you to sync iPhone with iTunes. Unless your keyboard has a high-power USB 2.0 or 3.0 port, you must connect iPhone to a USB 2.0 or 3.0 port on your computer.

Important: The battery may drain instead of charge if iPhone is connected to a computer that’s turned off or is in sleep or standby mode.

Show percentage of battery remaining in the status bar. Go to Settings > Battery > Usage, then turn on Battery Percentage.

See proportion of battery used by each app. Go to Settings > Battery, then tap Battery Usage.

The battery icon in the upper-right corner shows the battery level or charging status. To display the percentage of battery charge remaining, go to Settings > Battery > Usage. When syncing or using iPhone, it may take longer to charge the battery.

Battery icon with a lightning bolt indicates that the battery is charging

Important: If iPhone is very low on power, it may display an image of a nearly depleted battery, indicating that it needs to charge for up to ten minutes before you can use it. If iPhone is extremely low on power, the display may be blank for up to two minutes before the low-battery image appears.

Rechargeable batteries have a limited number of charge cycles and may eventually need to be replaced. The iPhone battery isn’t user replaceable; it should be replaced by Apple or an authorized service provider.