I downgraded to iOS9.3.5 thinking it'd help my battery life. A quick check on the BatteryLife app and its showing my capacity is at ~65% with 400 cycles. Heading to the Apple store... Year old iPhone 6s here. Any other user who ran iOS10 since beta 1 and is experiencing battery drain should downgrade, as the Battery Life app on iOS10 continuously shows 85% with 0 cycles, to check up on their battery health (or just take a trip to the Apple store). I was caught off guard by this, and perhaps the severe battery drain from the betas killed our batteries.