Quote Originally Posted by Louis View Post
You can use firewire cable for charging up to a certain capacity, but after the charge is complete, the higher voltage of the firewire will slowly damage the battery. So use it accordingly, may be one hour or two, and unplug it after.
This is true for about any battery, you can always charge it with a higher voltage, up to full charge, then you start to damage it, at a speed dependent on the amperes available from the charger. So, unplug the firewire when you see that the iphone is full.

Louis
Nope... the charger circuit has a very sophistocated voltage regulator circuit. It converts the input voltage to a very precise voltage to charge the battery. Firewire or USB, it does not matter. The charger circuit will automatically stop charging the battery when it is full. There are several protection mechanisms built in to prevent overcharging. LiPoly and LIon batteries get very angry when they are overcharged.