Q: iPhone 6 battery percentage unreliable

Hello to everyone! I'm using an iPhone 6 with the last iOS update (10.0.1 at the moment). Since iOS 9.3.4, I noticed an unreliability of my iPhone battery indicator.

During normal use, the percentage jumps down of about 10-15%. If in that moment I plug it in, the battery jumps up of about the same percentage. In other cases, the iPhone stays for a long period of time at the same battery level which can't be true, or it powers down even if it not at 1%.

I went to the Genius Bar and the Genius performed a diagnostic called "mobile inspector" which didn't reveal anything strange. The employee told me to calibrate my battery following these steps:

1) restore the settings (not data);

2) use the iPhone until it shuts down;

3) leave it there 2 hours without plugging it in;

4) recharge it up to 100% without using it and leave it there for 2 hours more;

5) repeat point 2 and 4 another time.

I have done what she suggested, adding a force restart after point 4.

The problem is still there. Two days ago, the percentage increased from 85% to 90% (without plugging it in) and yesterday it jumped down from 40% to 30% and then stayed at 3% for 1 hour.

I've booked a support call for this evening to see what I can do. The iPhone is still covered by the Italian 2-years warranty.

I encountered this problem some months ago. I went to a Genius bar and my iPhone has been replaced. I don't know if the Genius performed the same diagnostic tool or a more careful examination, but it recognized that the problem was due to the hardware, maybe due to the battery connector. They didn't replace the battery but gave me a refurbished iPhone.

Have anyone seen this problem and found a solution?

Thanks