In a hike you probably want to use your phone to look up the map/gps location, take photos etc. Ime iphones are struggling with this use case a bit without a power bank. Putting them in low power and airplane mode, while using a lightweight app for navigation with downloaded maps helps a lot, though it is still not gonna take you as far as other phones with larger battery life. I would never go for a hike where I know I need my iphone without a power bank with me. But not doing these and using google maps to navigate will not take you very far into the hike at all.