There are several things that you can do increase the life of a smartphone battery, especially an iPhone. One way is to make sure that all the background apps are shut down and that you only have your cycling app running. This is one thing that most people don't do and that will shorten your battery life if the GPS is running. I have been using an iPhone 4 and now a 5c for almost 2 years. My daily rides are between 35 and 45 miles and often 66 miles. I have never had a dead battery or the battery meter show below 50%. On my 5c, I normally have 80-85% battery life left after a 45 mile ride. You may want to do some internet searching to find out how to increase you phones battery life.