Why doesn't my iPhone's battery stay at 100% for as long as it used to?
Furnished content.
An old iPhone charged to 100% holds less charge than a new iPhone changed to 100%. Here's why.
Read more here
edit: Technology/auto___why_doesn_t_my_iphone_s_battery_stay_at_100__for_as_long_as_it_used_to_.wikieditish...