Dear all friends, thanks for your kind feedback on this D26 1600S light! Our engineers have made some tests on the D26 1600S. Above -7℃, the light works smoothly. Testing it below -10℃, the same issue may occur. It’s because the MCU manufacturer has built a low temperature protection mechanism into the chip. If you use the light in a low temperature water, it is suggested to use the special batteries that can be worked in low temperature conditions. Using the common batteries below -0°C, it will have a negative impact on on battery life and safety. And it’s also recommended that you could turn on the light before diving, so that the increase in internal temperature will offset the low external temperature to a certain extent. We will also consider to replace the the MCU without the low temperature protection mechanism on the light. If there is update, will share it.