The difference between a quartz watch and an automatic watch is the type of movement that runs the timepiece. A quartz watch is powered by a battery. An automatic is powered by perpetual motion.
A quartz watch runs by a battery-powered electronic movement that uses a low-frequency tuning fork that builds oscillation through an electrical current to create pulses to run the timepiece, according to Invention.smithsonian.org.
The automatic watch uses a spring-loaded mechanical movement with a balance shaped like a half disc that moves with the motion of wearer’s arm to keep the timepiece wound and operating, according to Timezone.com.
A quartz-powered watch gains or loses up to five seconds a year depending on the quality of the electronic movement.
An automatic watches can gain or lose up to eight seconds a day depending on the quality of the mechanical movement and its age.
A quartz watch must have its battery replaced every three to five years. A leaking battery could damage the watch.
An automatic mechanical watch must be oiled and serviced every five years. There is no battery to replace.