Batteries of IoT Long Range Wireless Temperature Humidity Sensor dying in a few days

Hi All,

I am experiencing some problems with my IoT Long Range Wireless Temperature Humidity Sensor setup, which consists of 30 sensors and a USB modem.

The problem is as follows: some sensors have their batteries fully drained after a few days already, whilst others seem to be fine (>70%). All sensors have exactly the same type of Alkaline batteries, all were replaced a week ago with rougly the same starting voltage (3.1 +/- 0.05 volts) (as reported by the sensors themselves).

The settings are also the same for all sensors (except for node ID):
Retries: 10.
Delay: 30 seconds.
Power mode: 4

I made 100% sure to leave none of them in config mode.

The curent status is that of the 30 batteries, 8 are without power again, whilst the other 22 are still at a self-reported 70+% (which is also on the low side I think, considering I swapped the batteries a week ago).

Does anyone have any idea what could be the cause of the sensors draining the batteries so fast?