Q: ios 9.3.4

Hello wirahamedi, 

Thanks for using Apple Support Communities. 

I see that since you upgraded your iPhone 6s, your battery is draining quickly and it is getting worse. I rely on my iPhone daily. So, I know how important it is to make sure that you have a battery that will hold a long charge. I have a few things that I would like you to try. 

First, use About the battery usage on your iPhone, iPad, and iPod touch and check the battery and app usage on your iPhone, and how to adjust settings to improve battery life, specifically, these sections:

Check battery usage 

Go to Settings > Battery. 

To see how long each app has been open and onscreen, and running in the background, tap . Under each app, you might see these usage types:

• Background Activity means that your battery is used while apps run in the background.
• Audio means that apps play audio while running in the background.
• No Cell Coverage and Low Signal means that your device is searching for a signal or being used with a low signal.
• Backup & Restore indicates that your device has been backing up to iCloud or restoring from an iCloud backup.
• Location and Background Location means that your battery was used when tracking your device.

 

      

Adjust settings to improve battery life

While viewing your battery usage, you might get a suggestion like Enable Auto-Brightness or Adjust Display Brightness. This is because iOS determined that changing these settings could improve your battery life. You can also see the usage times since the last full charge.

Use Low Power Mode

If you want to extend your battery life, turn on low power mode. This reduces power consumption until you turn it off or charge your iPhone to 80%. When low power mode is on, certain settings and features like mail fetch, Hey Siri, Background App Refresh, and some visual effects are reduced or disabled.

Then, use Maximizing Battery Life and Lifespan for tips on how to maximize the battery life and lifespan of your iPhone. 

Best Regards.