[Samsung Galaxy S7 Edge Accessories] dave457:
I know this is quite an old thread and most LED cases have now gone to heaven (or hell) but I still have one and I have been experiencing the issue and experimenting a little.

I think there are possibly two or three different reasons for the case not working, i.e. no LED display when closing.

The first one to mention maybe that broken cable in the lower spine of the case possibly caused by repeatedly folding the case open by 360 degrees for taking photos etc. In this case (no pun intended) just put it in the bin. Not much you can do with that.

It's true that Samsung cases (S-view and LED) use the sensors in the charging port for detection, even on the S6 Edge as well, so a faulty charging port (perhaps a fake one from China) could/will cause this problem.

The second scenario is where some software has affected the case's operation, Android update, app etc but this is still an unproven scenario.

The area I want to expand upon is where the LED case functions correctly on one S7 Edge but not on another. Ok, so we don't all have two phones to test this on but I do and this is the situation I'm in. It works fine on one but not on the other. I looked at all options including same version of the firmware on both (from Sammobile), factory reset, clear cache, but it still failed on one of my phones.

I was then researching on the internet about some people rested their S7 Edge on another phone (back of the S7E on the glass screen of another phone) and the LED on the case came to life. Interesting, I thought so I rested it on an iPhone 6S Plus and the LED case worked. I tried several phones, Nexus 6p, my other S7 Edge, Nexus 5X etc and the LED cover worked in all cases.

OK, so I could strap an iPhone to the back of my Samsung just to get the LED case to work. Hardly a solution but would surely look unique.

It's now clear that the power for the LED is gained from the phones battery by inductive methods. Initial communication is performed by NFC but NFC can be off for the LED case to function correctly. The case open/close screen on/off function has always worked because of the magnet in the inside, bottom part of the case.

So I went a stage further. As I repair mobiles for a hobby I have a number of old (and some new) batteries hanging around for various phones. I placed a battery from an iPhone 5S on the back of my S7 Edge case and I opened and closed the case and the LEDs worked. I tried all the old batteries I could find from various phones and every time the LED case worked correctly with a spare (non-connected) battery next to the rear of the LED case. This proves the point that the LED get power by induction, but obviously it was not working with the battery in my phone.

Obviously, one of the differences between my two S7 Edge phones is the battery and I can presume from my experiments that the battery in one of the phones is the problem. I have ordered a replacement battery from eBay, not a fake one from China, but a used one taken from an S7 Edge. When it arrives I will fit it and test the case again and report back, but I'm convinced the battery degrading or a fake replacement battery fitted at some point is the problem in my scenario.

So if you still have an LED case that doesn't work, try resting it on the screen of another phone and see if it works.

UPDATE

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Ok, I fitted another battery and the LED case now works correctly, so in my case it was a faulty or cheap/fake battery. All OK now