I disagree with this to an extent on solar. I haven't actually seen the iPhone battery, but generally, phones like that are going to be in the 6 watt hours per day range. A reasonable solar panel size to carry on the bike is about 1 watt, 5 watts is getting a bit too large. So you are going to need more then 6 hours of perfect sunlight, during the main riding part of the day. This will inefficiently charge a secondary set of batteries just to charge the phone, so you may be near 50% efficiency. Meaning, you really need 12 hours of perfect overhead sunlight. Impractical to impossible. If you can carry a large 5 watt panel, then you are going to be in a practical range needing a bit more then 2 hours of perfect light. Or you can just hook up to the motorcycle battery which is easily in the 150 - 250 watt hour range and pull the 8 watt hours for the phone. Which will be replaced in about 2 minutes of motor running.