My Shelly Door/Windows 2 lost power surprisingly fast and I'm wondering whether I should treat this as a battery problem or a shelly problem.
Here is the battery percentage over time. The DW2 was installed on 18 july with battery at 100 percent and stopped working on 18 august at a battery percentage of 92 percent. The graph also shows that the DW2 stayed at 99-100 percent from 18 july until 8 august. Maybe it is a coincidence, but it is worth noting that the door was not operated between 31 july aug 7 aug due to absence, so it looks like opening and closing the door causes significant battery drain (tilt is turned off). Is this normal?
Apart from the battery going from 100 to 92 in just ten days, it is particularly strange that the device seems to have stopped working at 92 percent. (At least it stopped sending battery level updates.) So I measured the voltage of the batteries (Panasonic Lithium CR123A, both with a best before date 01-2030): one was 0.84 V and the other 2.47 V. When I checked again a few hours later (during which they lay on my desk), they had recovered to 1.33 V and 2.56 V.
The fact that one of the batteries was basically completely drained while the other was still "ok" made me think that this was just a bad battery and that the problem will not occur once I replace both batteries. But even if this is true, I still find it strange that a battery can drop so extremely fast that the DW2 didn't even have time to report any battery level below 92 percent.
Does anyone have any explanation of what happened here or suggestions for what to do? (I have already replaced the batteries and the DW2 was immediately back online.)