I bought a smartthings bundle that includes the smartthings hub v2 in November 2016 from Amazon. Since then, I have been slowly expanding devices that connects to the hub. All good, until one night, there was a power fluctuation for a few seconds/minutes and I didn’t pay much attention because I thought the hub has battery backup. Since then, all sensors stopped reporting status (or hub not receiving status updates, either way). I had to manually take off all the sensors from doors and windows and manually reset them in order to reconnect (it was also a weird experience that the hub “thinks” they are connected, but they are not.)
So I thought the battery that came with the box maybe dead - measured them with a voltage meter and sure they were all dead (0.6v, 0.9v, etc.). I replaced the batteries with brand new batteries (measured 1.62v), then overnight, the brand new batteries were all drained again! The hub was connected to the UPS-backed power outlet the whole time!
The power supply that came with hub is a 5v power supply, but 4 batteries supplies 6v. I’m sure the hub has logic to check if power supply exists so don’t use battery - How long does your batteries last with the external power supply?