A solar-powered watch is a watch that is powered entirely or partly by a solar panel

Photovoltaic module

A solar panel is a packaged, connected assembly of solar cells, also known as photovoltaic cells...

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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 (Synchronar, Nepro, Sicura and some models by Cristalonic, Alba, Seiko and Citizen). In the 1990s, Citizen started to sell light-powered watches under the Eco-Drive

Eco-Drive

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.-Light as power source:...

 series name. They have developed the technology such that solar-powered watches are now a major part of their range of watches. Several other watch manufacturers offer similar watches or are developing such technology. These other watch manufacturers include (amongst others) Junghans

Junghans

Junghans Uhren GmbH is Germany's largest watch and clock manufacturer.The company is located in Schramberg, Baden-Württemberg. On 15 April 1861 Erhard Junghans created the company „Junghans und Tobler“ together with his brother-in-law Jakob Zeller-Tobler in Schramberg .The company began to produce...

, Casio

Casio

is a multinational electronic devices manufacturing company founded in 1946, with its headquarters in Shibuya, Tokyo, Japan. Casio is best known for its electronic products, such as calculators, audio equipment, PDAs, cameras, musical instruments, and watches...

 G-shock

G-Shock

G-Shock is a brand of watches manufactured by Casio, known for its resistance to shocks . They were, and continue to be, designed primarily for sports, military, and outdoor adventure oriented activity; for example, practically all G-Shocks have some kind of stopwatch feature, countdown timer,...

 and Casio Oceanus

Casio Oceanus

Oceanus is the elite line of Casio watches designed for both men and women. The line uses technology from both the G-Shock and Waveceptor watch series.-Characteristics:All Oceanus watches are known for the following key characteristics:...

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Typically, sunlight and artificial light are absorbed by a solar panel behind the crystal. The dial is either on a layer above or actually on the solar panel. This solar panel converts the light into electrical energy to power the watch. The watch will usually store energy in a rechargeable cell to power itself during the night or when covered such as by a person's sleeve. Citizen's watches use lithium

Lithium

Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...

-ion rechargeable cell to store sufficient energy to power the watch for several months/years of darkness. However, this (years) figure assumes that the watch enters a power-saving mode during which the seconds hand stops until the watch is re-exposed to light. Not all have a power save mode, yet will still hold a charge for typically 6 months, such as fairly uncomplicated (date only) analogs made by Citizen.

In the 1980s, inexpensive solar-powered watches hit the market and were popular amongst children, often featuring famous fictional characters such as Transformers

Transformers

A transformer is a device that transfers electrical energy from one circuit to another by magnetic coupling.Transformer may also refer to:* ASUS Eee Pad Transformer, an Android 3.2 Honeycomb tablet computer manufacturer by Asus...

 or G.I. Joe

G.I. Joe

G.I. Joe is a line of action figures produced by the toy company Hasbro. The initial product offering represented four of the branches of the U.S. armed forces with the Action Soldier , Action Sailor , Action Pilot , Action Marine and later on, the Action Nurse...

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