The Casio Solar Power Watch MDA-S11H-1BVEF is one of the Casio Solar Watches use the sun's rays to keep the battery powered via the Casio Tough Solar cell.
The Casio Solar Power Watch MDA-S11H-1BVEF solar conversion cell enables the watch to charge the battery whenever placed under indoor or outdoor ambient light.
When the Casio Solar Power Watch MDA-S11H-1BVEF is unused it will automatically 'sleep' until it is disturbed or placed in light. Once activated Casio Solar Watches then power up and display the correct time.