Eco-Drive
Encyclopedia
Solar powered watch
A solar-powered watch is a watch that is powered entirely or partly by a solar panel.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...
es manufactured by the Citizen Watch Co., Ltd. The first Eco-Drive watches were sold in 1995.
Light as power source
Most Eco-Drive type watches are equipped with a special titanium lithium ionLithium-titanate battery
The lithium–titanate battery is a type of rechargeable battery, which has the advantage of being faster to charge than other lithium-ion batteries. Some analysts speculate that lithium–titanate batteries will power electric cars of the future....
secondary battery
Rechargeable battery
A rechargeable battery or storage battery is a group of one or more electrochemical cells. They are known as secondary cells because their electrochemical reactions are electrically reversible. Rechargeable batteries come in many different shapes and sizes, ranging anything from a button cell to...
that is charged by an amorphous silicon
Amorphous silicon
Amorphous silicon is the non-crystalline allotropic form of silicon. It can be deposited in thin films at low temperatures onto a variety of substrates, offering some unique capabilities for a variety of electronics.-Description:...
solar cell
Solar cell
A solar cell is a solid state electrical device that converts the energy of light directly into electricity by the photovoltaic effect....
located behind the dial. The titanium lithium-ion composition precludes it from being affected from the regular charge/discharge cycle of other types of rechargeable batteries. Light passes through the covering crystal and dial before it reaches the solar cell.
Depending on the electronic movement model, a fully charged secondary power cell could run with no further charging anywhere from 30 days to 3,175 days (8.7 years), though most Eco-Drive men's watch models offer a six-month power reserve. If kept in the dark for too long, some movement models engage a hibernate mode, where the hands of the watch stop running but the internal quartz movement still keeps track of time. If an ample supply of light is given, the hands move to the proper positions and resume regular timekeeping.
Temperature difference as power source
Citizen Eco-Drive Thermo watches were introduced in 1999 and use the temperature difference between the wearer's arm and the surrounding environment as a power source. The rare Eco-Drive Thermo watches use the Seebeck effect to generate thermo electricity that powers the electronic movement and charges the secondary power cell. In the sun or in the tropics the ambient temperature can come close to or exceed the temperature of the wearer's wrist causing the watch to stop generating thermo electricity. In case no power is generated, an Eco-Drive Thermo movement will save power by moving the second hand in ten second increments until the production of thermo electricity is resumed.Hybrid Eco-Drive movements
Citizen also built an automatic quartzAutomatic quartz
Automatic quartz is a collective term describing watch movements that combine a self-winding rotor mechanism to generate electricity with a piezoelectric quartz crystal as its timing element. Such movements aim to provide the advantages of quartz without the environmental impact of batteries...
powered watch, the Citizen Promaster Eco-Duo Drive (released in December 1998). Novel to this watch was the use of both mechanical power as well as a solar cell to power the electronic movement and charge the secondary power cell. This model was an attempt to enter higher-priced markets (at a cost of around $1,000 USD). The Eco-Duo Drive technology failed to attract consumer interest and Citizen has since stopped making use of the unique movement.
Solar cell and secondary battery life expectancy
According to Citizen, experimental data showed the solar cell and secondary battery will last for more than 10 years. According to Citizen Europe, laboratory tests showed that after 20 years the secondary battery retains a power storage capacity of 80% of its initial capacity.Maintenance
For water resistantWater Resistant mark
Water Resistant is a common mark stamped on the back of wrist watches to indicate how well a watch is sealed against the ingress of water. It is usually accompanied by an indication of the static test pressure that a sample of newly manufactured watches were exposed to in a leakage test...
and diving Eco-Drive watches Citizen recommends a watch gasket
Gasket
thumb|sright|250px|Some seals and gaskets1. [[o-ring]]2. fiber [[Washer |washer]]3. paper gaskets4. [[cylinder head]] [[head gasket|gasket]]...
exchange every 2 or 3 years to preserve their water resistance because watch gaskets which form a watertight seal degrade as they age.
Further Citizen recommends maintenance for Eco-Drive watch movements in regular intervals in order to extend the life of the watch movement, since the gears used in running watch movements are subject to slow wear.
Citizen states that their lubricant
Lubricant
A lubricant is a substance introduced to reduce friction between moving surfaces. It may also have the function of transporting foreign particles and of distributing heat...
s for Long-Lasting Precision Equipment when used in watches, timepiece movements remain smooth for a long time as the oil does not harden even after 20 years.