Eco-Drive

This article is about wristwatches. For "eco-driving", see Fuel economy-maximizing behaviors.

Citizen Promaster Eco-Drive AP0440-14F Diver's 200 m. Four solar cell segments are just visible under the dial. Manufactured in 2000.

Citizen Atessa Eco-Drive ATV53-3023 analog-digital chronograph with 4 area Radio Controlled reception (North America, Europe, China, Japan).

Eco-Drive is the series name of a line of mainly light powered watches manufactured by the Citizen Watch Co., Ltd. The first Eco-Drive watches were sold in 1995.^[1]

Light as power source

Most Eco-Drive type watches are equipped with a special titanium lithium ion secondary battery that is charged by an amorphous silicon solar cell located behind the dial.^[2] 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.^[3]

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.^[4] 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.^[2]

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.^[5]

Hybrid Eco-Drive movements

Citizen also built an automatic quartz powered watch, the Citizen Promaster Eco-Duo Drive (released in December 1998).^[6] 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.^[7] 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.^[8]

Maintenance

For water resistant and diving Eco-Drive watches Citizen recommends a watch 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.^[9] Citizen states that their lubricants 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.^[10]

See also

• Watch
• Solar powered watch

References

1. ^ "History of Citizen Watch". Citizen.co.jp. http://www.citizen.co.jp/english/csr/history.html. Retrieved 2009-08-22. 
2. ^ ^{a b} "EcoComp-pf06a_h01-04" (PDF). Archived from the original on 2007. http://web.archive.org/web/20070929154920/http://citizen.jp/complication/images/catalog/164aw_catalog.pdf. Retrieved 2009-08-22. 
3. ^ "History of the Solar Wristwatch". Soluhr.com. http://www.soluhr.com/. Retrieved 2007-01-17. 
4. ^ Loading properties of Eco-Drive watch movements (German)
5. ^ "Citizen Eco-Drive Thermo watch". Pmwf.com. 2004-02-13. http://www.pmwf.com/Watches/WATCHSALES02/CitizenEcoDriveThermoWhiteFeb04/CitizenEcoDriveThermoWhite.htm. Retrieved 2009-08-22. 
6. ^ "History of CSR Activities". Citizen Watch Co.. http://www.citizen.co.jp/english/csr/history.html. Retrieved 2007-01-18. 
7. ^ Citizen Service & Support FAQ Eco_Drive
8. ^ Citizen Watch Europe GmbH: ECO-DRIVE Technologie (German) (archived 2007)
9. ^ Citizen Service & Support FAQ Eco_Drive
10. ^ "Products for CITIZEN" (PDF). http://www.citizen.co.jp/english/csr/env/pdf/2004pdf/006_eng.pdf. Retrieved 2009-08-22. ^{[dead link]}

External links

• CITIZEN Eco-Drive site
• Interactive Citizen Eco-Drive Setting Instructions
• NEW FROM CITIZEN: hand-assembled quartz movements by Joe Thompson, WatchTime Magazine April 2006