The battery inside the WakaWaka Power+ is a high-temperature LiPo battery. This type of battery is resistant against operation at elevated temperatures, but like other LiPo batteries, it cannot be charged when the temperature drops below freezing (0 degrees C). Therefore, the electronics inside the WakaWaka Power+ will prevent charging at temperatures below freezing. The product can still be used as a light source, or to charge a phone, between 0 degrees C and -20 degrees C. However, please keep in mind that the battery performance will be temporarily degraded below freezing, so the amount of energy available will be less compared to a test performed at normal room temperature (25 degrees C). This also applies to the WakaWaka Light and WakaWaka Base.