My phone was showing 1% battery life this morning when I got up (down from 36% at bedtime). I shut the phone off while I was at the gym, then turned it back on when I was ready to leave. Upon turning it back on, the battery life was showing 30%. On the drive to work (20 minutes), it quickly drained down to 20% even though I had it plugged in to the USB charger on my car stereo. I shut the phone off again at work, and when I restarted it the battery indicator was showing 33%. So basically I have no idea what the actual battery life is now because it changes drastically with each restart. This has never happened before, which make me wonder if it's related to iOS 11.2.6 (iPhone 7). Any thoughts?