Q: Plug charger in Battery case with iPhone 6s = black screen

Hello there, Milkfree.

It sounds like your iPhone 6s is not waking when charging in the Apple Smart Battery Case. The steps you have followed to resolve are great step so far. The following Knowledge Base article offers a few more recommendations for troubleshooting:

If your iPhone, iPad, or iPod touch doesn‘t respond or won‘t turn on

If your screen is black or frozen

First, try to force your device to restart.

• Forcing your device to restart won't erase the content currently on your device.
• You can force your device to restart even if your screen is black or your buttons aren't responding.

Press and hold the Sleep/Wake and Home buttons at the same time for at least 10 seconds until you see the Apple logo.

If your device still won't turn on or start up

Plug in your device and let it charge for up to 1 hour.

After a few minutes, you should see the charging screen.

 

If you don't see the charging screen within an hour, or you see the connect to power screen, check your connector, USB cable, and power adapter. Make sure that everything is plugged in firmly, free of debris, and not damaged. You might want to try a different USB cable or power adapter.

 

If your device still won't turn on, see what to do next.

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What to do next

Contact Apple Support to set up service if you have any of these issues:

• You still see a black screen after charging, force restarting, or following the steps in this article.
• You see a black screen, but can hear alerts, sounds, and vibrations.
• Your screen is on, but it doesn't respond to when you tap, slide, or try other gestures.
• You can't force your device to restart because your Home button or Sleep/Wake button is broken or stuck.
• Your device is stuck on the Apple logo, displays a solid color, or isn't recognized in iTunes.

Thanks for being a part of Apple Support Communities.

Kind Regards.