iPhone 6s iOS 12.3
Battery Maximum Capacity 92 percent
Battery Replaced by Apple 02/2018

Apple Watch 2 Watch OS 5.2
Purchased 09/2017

The other day, as a matter of routine, I put my iPhone into low power mode as soon as I woke up. Why? Because otherwise it will need a recharge long before days end.

When I left the house at about 7:00 AM, both the watch and phone were at 100 percent. I started the Strava activity tracking app on the watch and set out for a morning of bike riding. I stopped many times; to eat, for a coffee, to explore on foot, etc. during the ride I only used the phone to take a dozen photos and two 15 second videos. I consulted Google Maps exactly once. A couple of messages to and from my wife. Thats it. No music. No phone calls

When I got home at 11:30 AM, the phone had 22 percent left and the watch 27 percent. This phone that lost almost 80 percent of its battery charge in 4  hours while in Low Power Mode and with hardly any use.

When I later checked a screenshot of the Battery condition I noticed that the usage graph showed 45 minutes of usage between 10 and 11:00 AM. This is weird. At that time my phone was in my bike bag for the entire hour as I was peddling home.

(I thought this might be because I had "Raise to Wake" active. I have since turned it off, with no effect on battery usage.)

Although this was an uncommonly bad day for both devices, it is not unusual for my phone to lose most of its battery charge in just a few hours. The next morning I left the house at 9:00 AM with the phone still in the charger when I picked it up. I put the phone in low power mode. Thirty minutes later, when I reached the destination coffee shop, the phone was already down to 80 percent and was down to 70 percent by the time my cappuccino was delivered.

Yesterday morning my wife and I set out by bicycle for breakfast. When we started, both her X and my 6s showed 100 percent battery charge. When we arrived, 20 minutes later, her X was still at 100 percent, but my 6s, still in Low Power Mode, was at 78 percent. Both of our phones are paired with an Apple Watch and both of us were using Apple's Workout app on the watch to record our ride to breakfast.

I can't help but think that this rapid battery drain may be due to either something I've done to the phone or is somehow related to being paired with an Apple Watch.

Any ideas?