Safari eating up battery iphone 6s IOS 12.1.2

I took the phone in this afternoon to the local Genius Bar. The tech wanted to change the battery and reset the phone. He said that software could be causing the problem - hence the reset - but that it could also be the battery (85%). I could avoid another trip back if it is the battery. Doing both at the same time would have been too many variables for me, so I chose to just reset the phone while I was there. If I continue to have a problem, then I might consider replacing the battery. If there are any new developments, I will post them here.

Yes, I have done all of the above. The only thing I have not done is a hard reset. I've decided to bring it into the Genius Bar on Wednesday. I am pretty sure a hard reset will work, but I will let you know.

Yes, I have seen posts where people have replaced the battery to no avail. I am not planing on doing that. I am hoping that as an informed consumer, I can find out exactly what the is causing the bug. I will report back to this thread. I am going in tomorrow afternoon - weather permitting.

Just wanted to update you on my iphone 6s battery. I have since added back most of the apps that I used. The battery seems to be holding the charge much longer than it did before I reset it. The only problem that I had since then was when I left it charging near an open window overnight (outside temp was below 32 degrees). the battery did not like this and was completely discharged even though it was connected to the charger. However, it recharged in no time once it warmed up.