Never change a battery again! The Obaku solar series are powered by any light source and will keep running as long as you use the watch. Once the watch is charged it will keep running on the regular recharge it takes from wearing it in any light source. If you do not wear it for a while and have kept it in a dark place, simply put it in an artificial light source for 72 hours or in direct sunlight for 8 hours and it will be fully recharged. This is the most environmentally friendly watch option, as no batteries are needed and the watches are automatically recharged. Get yours now!