Will my iPhone 5's battery weaken when I'm not disconnecting it from the charger though it's fully charged?
Or if the iPhone is already battery full, will it change it's power source automatically to AC to prevent overchanging?
I believe it stops charging once the battery is full, then just runs off the charger until it's unplugged
Leaving the device on the charger will have no affect. iOS is designed to cycle the battery when left charged so you may notice it dip to 99 or 98% before recharging to 100% several times if left on the charger for extended periods of time.
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