Electronic Watches are powered by watch batteries or a battery / capacitor recharged by a solar-cell or kinetic movement
Electronic Watch Movements or displays are powered by batteries or capacitors
Electronic movements have practically no moving parts by utilizing the piezoelectric effect of a quartz crystal to provide the timing for the display, being referred-to as quartz watches. Most quartz watches have a non-moving electronic displays, with only a very few driving moving hands.
The first production digital quartz watch was made by the Seiko Watch Company.
Electronic Watch Accuracy
Electronic movements have few moving parts as in a battery powered movement using a tuning-fork oscillator.
The most precise battery-powered watch and the 1st one on the Moon was produced in the 1960s by the Bulova Watch Company.
Digital Watch Batteries
The source of power in most instances for a digital watch is a battery Some electronic watches are also powered by the movement of the hand. Kinetic powered quartz watches make use of the arm movement by turning a rotating weight, which powers a miniature generator to recharge the battery powering the watch.
Watch batteries are designed to be very small and provide minimal power for long periods (several years or more) of time. Replacing the battery is relatively easy, using a few simple tools, while most people still take a trip to a watch-repair shop or dealer; especially for watches that are designed to be water-resistant, for the special tools and procedures needed to ensure that the watch remains water-resistant after battery replacement.
Power Source Alternative to Watch Batteries
Solar powered watches are powered by light that recharges a battery. A photovoltaic cell on the face (dial) of the watch converts light to electricity, to recharge a battery or capacitor. The movement of the watch gets its power from the recharged battery. As long as the watch is exposed to light or sunlight, it seldom needs battery replacement. Most models only need a few minutes of sunlight to provide for weeks of power, as in the Eco-Drive model by the Citizen Watch, Casio Watch and Seiko Watch Companies.
Some of the early solar watches of the 1970s had innovative and unique designs to accommodate the array of solar cells needed to power them made by Seiko and Citizen. Over time the solar cells improved while the power needed by the movement and display got less and solar watches started to look like conventional watches. A novel power source is the temperature differential between the wearer's arm and the surrounding environment as designed into the Citizen Eco-Drive Thermo.
Time Display and Battery Power Demands
Traditionally, watches display time in analogue form, with rotating hour and minute (sometimes seconds) hands over a dial showing time indicators. Watches powered by quartz usually have a second hand that jumps one increment every second.
Watches with Digital Light Emitting Diode (LED) displays required pressing a button to see the time for a few seconds, since LEDs used too much power to operate continuously thereby requiring frequent and expensive battery changes. Later LED displays were replaced by Liquid Crystal Displays (LCDs) as used by watches made by the Casio and Timex Watch Companies, which use far less battery power and were more convenient with the time visible without needing to push a button.
Some watch models use a kinetic drive mechanism to recharge a battery or capacitor to provide power to the watch.
Multiple Watch Functions
All watches provide the time of day by showing the hour and minute, and sometimes seconds. Many also provide date, and day of the week. Many watches include alarms, and sounds to know the time by the sounds coming from the watch. The more functions a watch has, with sounds and alarms, the more power it usually requires, thereby reducing the battery life. As a result, the more complex a watch is and the more features the wearer uses, the more important it is to use a fresh and powerful battery.