Thanks, Ian. I just don't make 15mph on the flat, mainly because we don't have that many flats, except for one stretch of about a mile right here in town on the way to a common meeting place for our rides, where I'm always in a hurry because I hate being late. But the automatic on-off charging control, between the phone and the lamp, seems encouraging. It would be worthless if the phone just turned off when the charge got too low, and didn't turn itself on again. The iPhone 4S, which is the model I use, appears to take a very fast charge when sucking current from the wall wart. It would be useful to have some observation when you have more experience about how fast the phone charges up a 10% segment, or 20% or whatever is easiest to observe, in mixed riding, definitely less than 15mph. I'm not planning on killing myself with unnatural high speeds to keep my phone charged!
As a general observation, I'm not surprised by your findings so far. The iPhone can be observed in everyday use to last reasonably well in standby mode but to drain the battery fast when an app is used, and much faster as more apps are used. All that processing and communications power doesn't come free.
Thanks again.
Andre jute