Just fill the tank with tap water, add a splash of natural lemon juice, and youâ€™re set for 8 to 12 weeks of accurate timekeeping. Fun, functional and eco-friendly, the Bedol Water Powered Clock is ideal for home or office, or as a great little gift item. Don't ask us how but something about the acid in the lemon juice works like a battery. Sure. Whatever the ways, we like the means.