IAM-T1 Battery drain

According to the description, the IAM-T1 has 18 months of battery life.

With the originally supplied batteries, my IAM-T1 reports “battery very low, please replace” after less than 2 weeks !

Has anybody else this problem ?

Can it be a hardware problem of my device ?

Is there a firmware update available to solve this problem ? (The app displays nothing, when I press the firmware update button)