Effects of Current Fluctuations on Charging iPhones, iPad, etc, all have their optimal specifications for charging. A power source that does not meet those specification results in a slow charge. However, what happens when the specifications (volt/amps) increased &amp; decrease (fluctuate)? Will the power fluctuations cause damage to the battery? Assuming there is a voltage regulator to keep it from going too high, will this still cause damage?
Connecting directly the solar panel to your iPhone will have negative influence on your battery. 

Solar system that are design to charge the phone/GPS/what so ever, use a second battery as buffer. Do you use a system that has not one.