The batteries inside the WakaWakas are high-temperature LiPo batteries.
A solar powered device should be able to withstand the sun! That’s why we designed the WakaWaka to be very capable of withstanding temperatures up to 80°C (175 °F) without problems. When it reaches higher temperatures the internal system will shut down to protect itself. You can best put it in the refrigerator to cool it down if this happens.
The LiPo batteries in the WakaWakas cannot be charged when the temperature drops below freezing (0°C). Therefore, the electronics inside the WakaWaka will prevent charging at temperatures below freezing. The Between 0 and -20°C the WakaWaka can still be used as a light source, or to charge a phone. 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°C).