I have an Iphone 5S with IOS 11.41. It's old, but I don't really like updating because the newer software does not run well on older phones. Lately the phone's battery seems to drain when I'm traveling to work. It's a 40 mile commute and this even happens when I have no apps running. It will go from 80-100% to 10-20%. When I'm at home this isn't a problem. I also have wifi at home, not sure if that means anything. Any ideas?