Citizen have harnessed the light around us to create watches that never need a battery, adding extra utility and function to their entire range, from slim, elegant dress watches, to sporty but stylish functional watches, for him and for her. Eco-Drive graces the majority of their models on sale today, having first been offered in 1995. The success of this was astounding, and more and more models have been added to their range in place of traditional quartz watches. The technology used has evolved vastly, improving the system for millions of people wearing Citizen Eco-Drive watches to the present day.
The watch is a quartz movement at heart, an electric charge passed through a shaped quartz crystal, causes it to vibrate at a rate of exactly 32768 vibrations per second, or 2^15Hz. This precise rate of vibration allows a vastly more accurate rate of time measurement than any mechanical watches, even the best chronometers.
How does Eco-Drive work'
The Eco-Drive innovation is a silicon light cell, like a solar panel, behind the dial. Although faintly visible on some models, it is mostly hidden to the wearer, but the glass and opaque dial allow enough light, both solar and artificial, to pass through to the cell and generate the electricity required to power the movement. This also charges a titanium lithium ion battery, designed to be charged and discharged repeatedly without affecting or varying the voltage to the quartz crystal, and without losing its capacity to store energy even after decades.
The battery allows the watch to store energy until it does not have sufficient energy from the solar cells to power the movement, at which point it moves to the energy reserves without skipping a beat or losing any time.
Diagram of Eco-Drive in Action
Early models could last more than 30 days from full charge without light, even in the relative infancy of the technology, and still maintain perfect quartz accuracy. Most modern Eco-Drive watches have an average of 6 month power reserve, more than adequate even as an occasional watch, but have been known to offer up almost 9 years of power reserve!
Some models feature a hibernation mode, when they have not received light for a long period, and the hands stop moving. Even though it does not show the time, the memory of the watch allows it to spring back into action, displaying the correct time within a few seconds of exposure to light again.
Eco-Drive is not just for standard analogue watches, it is fitted to a vast number of models available today, with a multitude of motorised functions, including Perpetual Calendar models, Fly-Back Chronographs, such as the Calibre 2100, and even the radio controlled Sky-Hawk A-T models, with back light, multi-motor analogue as well as digital displays to power and an atomic clock signal receiver. At the other extreme, they are also fitted into every elegant Stiletto model, making them the world's thinnest light powered watches, at under 3mm thick, yet still allowing a substantial power reserve and faultless Eco-Drive quality.
Citizen believes in their products, the technology and especially the quality, having constantly developed these attributes since 1925, and therefore offer their 5 year worldwide guarantee on every model, including all of the Eco-Drive range.
Because of the constantly recharging battery, it is more environmentally friendly as there is no disposal of lithium batteries to harm the environment. This also saves money and time in the long run for the customer. To add to the environmental credentials, both Eco-Drive and standard quartz Citizen watches are presented to the customer in presentation boxes largely made from recycled materials.