Eco-Drive watches were Citizen Watch Company’s answer to never having to change a watch battery again. Eco-Drive watches use a solar conversion panel and a special energy storage cell that uses light from any source to generate electrical power. Through a photovoltaic process, the light shone through the watch dial is converted and then stored in the cell. Each storage cell can be charged and recharged throughout a lifetime of use and will run continuously as long as it is exposed to bright light. If light is not available to a fully-charged watch, the cell will run anywhere from 45 days to 5 years depending on the model. The average model has a 180 day power reserve. While light is necessary to keep the Eco-Drive watch running, excessive heat can damage the watch. Eco-Drive watches should not be charged on the dashboard of a car or less than two feet from a lightbulb.The average quartz watch uses a silver oxide battery as its primary source of power, which can not be recharged. The Eco-Drive watch does not contain any of the same chemicals used in ordinary watch batteries, an added environmentally friendly bonus.