@ jazlichy
In a parallel thread on the SNZB-03, I posted my experience with trying to operate a SNZB-03 outside in a Minnesota winter, where there are extended periods of outdoor temperatures below 32F (0C).
This week, overnight temperatures are dropping to -10F(-23C) and daytime highs are just getting into the single digits above 0F (-17C).
I tested the 2 Sonoff SNZB-03 units I have.
The first unit I tested started self-triggering when the outside temperature dropped below 26F (-3C).
The second unit worked until the outside temperature dropped below 10F (-12C).
When I brought them inside, they continued to malfunction until they warmed up.
I noticed that when they were malfunctioning, their battery voltage was way down to around 50%.
As they warmed up, I watched the battery Voltage recover. The units functioned normally once the battery Voltage had recovered to around 60%.
I didn’t grab screen shots of the SNZB-03 battery Voltage when this was going on, but I have captured the battery Voltage graphs of Sonoff SNZB-02 temperature sensors during our cold weather this past weekend. Note how the battery Voltage kept dropping and dropping as the temperature fell.
I replaced the battery before the SNZB-02 battery went dead and I lost the data from the sensor.
The same CR2450 coin batteries are in all these Sonoff sensors, and I believe we can expect the same behavior in cold temperatures.
I looked up the specs of the PIR sensor I believe is in the Sonoff units (3 pin, through-hole, metal can, PIR sensor with square window on top).
It’s operating specs list functionality down to -40C!
If true, the PIR sensor shouldn’t be the failure point.
https://www.murata.com/~/media/webrenewal/products/sensor/infrared/datasheet_pir.ashx?la=en
My conclusion is that the self-triggering is caused by sagging battery Voltage, due to cold, and the CC2530 Zigbee chip is probably rebooting over and over, transmitting the trigger signals over and over.
My proposed solution is to open up the unit and solder an external AA battery holder to the battery terminals.
2469 Keystone Electronics | Battery Products | DigiKey or
https://www.amazon.com/dp/B076C7S2VN
Two AA batteries (especially lithium AA batteries) should maintain a lot more reserve current when the temperatures drop below 26F (-3C), and thus the Voltage won’t drop to reboot levels, and it will continue operation in the cold. It will be ugly to have a battery holder hanging outside the unit, but I suspect this will solve the cold coin battery problem.