Overcharging iPhone battery

The battery will stop charging when it reaches 100%

Stedman

Apple devices run on Lithium-Ion batteries that are programmed to cut their charging voltage and trickle charge after reaching a 100% charge. Li-ion batteries are also programmed to very slowly discharge to prevent overcharging and exceeding their charge limit. The process consists of a charging state at full current until they reach %100, then to a charge balancing state, finally to a very low voltage trickle charge state to prevent the battery from being damaged. Although there are rumors floating around about the new iPad screwing up during the charging process and overcharging and damaging the battery and other rumors about it undercharging nothing has really been accepted by Apple yet. But regarding the iPhone, there have been millions of people that have yet to have an issue with charging so I'd say you're in the clear, charge away. I keep my phone plugged in all night on my nightstand and have never had an issue. Besides from my experience with electronics, Li-ion batteries prefer to stay plugged in whenever possible. They slowly loose their ability to charge over time and the less stress you put on them the longer they will last. Also as a tip, try not to let a Li-ion go completely dead over and over again, this can mess up the batteries memory state and cause it to hold way less of a charge then it should. Nickel-Cadmium batteries where the ones you had to fully discharge then recharge but most Li-ions and their devices (mostly computing devices) have circuits that will automatically recallibrate the batteries memory for you when you leave them plugged in for extended periods of time.