There shouldn't be any major problems or slowdowns running iOS 15 on an iPhone 7, but for battery and other reasons (starting with "this is almost certainly the last supported OS for your phone"), you should probably be thinking about/planning for its replacement.There have been a few updates already, fixing some of the initial bugs, and it is presently at 15.1
That’s only partially due to the OS updates. The real culprit is that your battery is being asked to work harder and more efficiently, but it is also degraded and old. Replace the battery, and I predict you will see improved performance.I've had huge battery issues with iPhone SE first gen starting with the 14.1 update, 15.1 even worse.
So, in other words, the battery health isn’t really 91 percent. It has degraded to the point where the software algorithm can't accurately assess its state.Thanks Chas,
Even though the battery Health is 91%? I have to recharge the phone several times/day as it drops to 1% very quickly & with little use.