How It Works
The watch that never stops, wherever you are.
Inventing a technology to ensure watch that never stops anywhere in the world was one of the challenges for CITIZEN.
In 1976, we invented the world’s first light-powered analog quartz watch that runs using only light as a power source. This technology, now known as “Eco-Drive,” can generate power from any light source, artificial, natural and even dim light to keep watches running without ever replacing batteries.
As a pioneer of the field, we set new challenges for ourselves to bring forth the full potential of power generation using light.
CITIZEN’s Eco-Drive technology has won acclaim in Japan and other countries for its contribution to environmental protection. In 1996, an Eco-Drive watch was nominated as the first watch to qualify for the Eco Mark, a label managed by the Japan Environment Association (JEA). In 2014, CITIZEN became the first watchmaker to earn a Gold Prize in the JEA’s Eco Mark Awards.
Features of Eco-Drive
Watches Powered by Light
Easy to charge even in Low Light
Eco-Drive is designed so that any light source, no matter how dim, will generate the energy needed to power the watch.
Light itself is the only energy source required to tell the time with an Eco-Drive watch.
Darkness is not a Concern
One of the factors that distinguishes CITIZEN’s Eco-Drive from other methods of keeping watches running at all times is its “power life.”
The majority of Eco-Drive watches continue running for more than six months* on a full charge, even in total darkness.
Selected CITIZEN watches feature a power saving function which allows them to run for up to seven years without exposure to light.
*Some older models may have a shorter power reserve.
Eco-Drive efficiently converts any light, including artificial, natural and even dim light, into energy. CITIZEN has focused its development efforts on two different types of solar cells.
This ring-shaped solar cell wraps around the dial and also converts light into energy efficiently. It allows more design flexibility on the dial, as the dial surface does not need to be transparent to allow light to pass through.
This is the most commonly used solar cell in CITIZEN’s watches today. It converts light into energy with high efficiency because it sits under the dial.
CITIZEN has dedicated itself to improving its technologies for energy saving watch movements. Our pursuit of innovation has allowed us to bring to the market many light-powered watches with advanced functions and designs.
Insufficient Charge Warning
When an Eco-Drive watch with this feature is left in the dark, some or all of the hands stop in order to conserve energy. Once light hits the watch face, the hands move quickly and automatically back into position to display the current time.
Power Saving Function
When an Eco-Drive watch with this feature is left in the dark, the hands stop in order to save energy. Once light hits the watch, the hands move quickly and automatically to catch up to display the current correct time.
CITIZEN continues to work on the further enhancement of semiconductor chips, circuits and motors in its watches to even further reduce the power consumption of watch movements.
Light-Level Power Indicator
CITIZEN invented the world’s first* Light-Level Power Indicator for analog watches. It detects the intensity of light striking the dial and displays the electricity generation level at the moment, allowing wearers to easily gauge the charge level in any given situation.
* According to research data from CITIZEN WATCH CO., LTD.
Energy for the Future
The Energy Crisis of the mid-1970s was one of the triggers that started CITIZEN on the quest for viable alternative energy sources. The social backdrop of the time led us to develop a “light-powered watch” that could run on the power of sunlight.
By the 1970s, battery-powered quartz watches had established the dominant market position in the Japanese watch market and became the most popular watches available. At the same time, CITIZEN noted several potential issues with quartz watches, such as a limited battery life, which would require periodic battery replacement, and the environmental impact of disposable batteries.
First Light-Powered Analog Watch
Early solar cells were too bulky and easy to break for wristwatches. However, reducing their size was thought impossible by CITIZEN’s R&D department.
In 1974, CITIZEN completed its first prototype of a light-powered analog watch with a round solar cell embedded in the dial. Two years later, in 1976, the Crystron Solar Cell, the world’s first light-powered analog watch, was launched.
Crystron Solar Cell, the world’s first light-powered analog watch
The Watch that Never Stops
Watch that could operate for 200 hours on a full battery charge
When the Crystron Solar Cell was brought into the market, solar cells and secondary batteries to store the surplus energy they generated were limited in terms of generation capacity. The product life was shorter than that of battery-powered watches, which continue ticking away regardless of the time of day.The increasing demands for secondary batteries and the growth of light-powered products among many industries during the 1980s drove CITIZEN’s engineers to advance their technologies and pursue further improvements in light-powered watches. After strenuous development efforts, CITIZEN introduced the world’s first industrial watch that could run up to 200 hours on a full battery charge.The development of thinner solar cells that could utilize room lighting, as well as sunlight, and more resilient electric double-layer capacitors inspired CITIZEN’s engineers to continue improving light-powered watches.
Then, in 1995, CITIZEN added a secondary lithium-ion cell for power storage, resulting in a light-powered analog watch that runs for six months or more on a full charge.
CITIZEN’s brand statement—Better Starts Now—was the motivation behind the many world’s firsts recorded by our company. It continues today with our pursuit to develop even more exquisite light-powered watches designed with diverse functions and materials all with the goal of improving the pleasure of wearing a watch.
The world’s first light-powered Eco-Drive divers watch
The world’s thinnest * light-powered Eco-Drive Radio Controlled watch* 4.9mm thick at the time of release in 2010
The world’s smallest* light-powered Eco-Drive Radio Controlled watch * 24.5mm radius at the time of release in 2010
Light-powered Eco-Drive watch, which takes in light from the side of its case
The world’s first Bluetooth light-powered Eco-Drive watch
Note : There are models which are no longer in production or not available in some markets.