no battery needed for environ friendly,just add water and it works.

The Amazing Water Powered Clock is a true environmentally-friendly green product, keeping time without the need for any electricity, batteries or solar cells. Built into this compact and attractive design is a large digital LCD display that is powered by nature, using water or any electrolytic fluid such as fruit juice, coffee, beer and soft drinks as the power source. The intriguing internal energy converter applies the concepts of over-potential and charge transfer to pull electrons from the molecules within the fluid and converts them into an electric current which fuels the LCD display. Once the liquid chambers on the back of the Amazing Water Clock are filled, the LCD screen will light up. With easy to use mode and set buttons, you will be able to set the time and date within minutes and enjoy this fun, educational and pollution free product as long as you keep it filled.