While an autopsy, undertaken the same day Presley died, was still in progress, Memphis medical examiner Dr. Jerry Francisco announced that the immediate cause of death was cardiac arrest. Asked if drugs were involved, he declared that drugs played no role in Presley's death.
Power Reserve notification (left), Charging the Apple Watch (middle and right). As for charge times, Apple says it takes about 1.5 hours to reach 80% and up to 2.5 hours for a full 100% charge. Real-world Watch battery performance.
Apple Watch is supposed to have 18 hours of battery life, which would translate into a full day if I were to ever keep to a normal sleeping schedule. I was able to lengthen the uptime of my watch to a full 24 hours on days in which I didn't make battery-taxing phone calls with it, or use the half-as-power-hungry heart rate monitor.