Originally Posted by
3speed
Do you find that if you have your phone charging in while you ride for the day, it'll charge up all the way, assuming almost dead from use the night before?
Depends.
I can travel weeks on end navigating with a smartphone (always on) strictly powered by a dynamo hub. Now, it may require "power management". i.e. if the terrain is hilly such that average speed drops to, say, less than 10mph (16kmh), it may be wise to turn off the phone display to reduce power consumption, and turn it on just before reaching the next waypoint. Which is why I ride with a small/cheap bike computer to independently keep track of distance.
Another way to answer is: a fully charged phone, display on, consumes roughly 3.5 Watts. My rig (Shimano XT dynamo hub + Forumslader USB charger) produces that amount of energy at 12 kmh.