M.best Waterproof 4.8M/16FT 20 LEDs Blossom Double Lotus Fairy Solar String Lights Flower Lighting for Garden Home Christmas Party Wedding Decoration (Multi-Color) With memory function. You could choose the mode you prefer. And it will be kept under the same mode when you turn it on next time. Converting solar energy into electricity, the solar panel charges the battery during the day and the built-in sensor turns on the light automatically at dusk. With built-in NI-MH battery, this string light is totally waterproof, it can still work in the rainy or cloudy day if the sunlight is not available. To maintain a long using life, please do not use it in the water. Make sure the switch is turned to "ON", if not, the battery will not be charged.