Update: I did a full charge cycle (charging, then discharging) with the batteries. Charched them again, tested the AudioMoth with the same settings, and all of the devices (except for 1 out of 21) worked normal again.

Great stuff, thanks! I also found the AudioMoth-Utils on Github which I have already succesfully tested. I'm mostly working with Python, so an expansion function in Python would be great (as I'm not skilled enought to write it myself). But for now I can just call the JavaScript function from Python and expand my files like that. Best regards! :)

Thanks again for the detailed response. We are using AM 1.1, which might also have been a contributing factor to the failures. We used the same SD cards last year, and the batteries were all fully charged a couple of days before deployment. The only reasonable explanation seems to be that the batteries were not handled and/or stored ideally, and therefore lost capacity. NiMH batteries can be quite fickle, from what I've read...

Thanks again for the detailed response. We are using AM 1.1, which might also have been a contributing factor to the failures. We used the same SD cards last year, and the batteries were all fully charged a couple of days before deployment. The only reasonable explanation seems to be that the batteries were not handled and/or stored ideally, and therefore lost capacity. NiMH batteries can be quite fickle, from what I've read...

Thanks for the response! We chose the amplitude threshold consciously and it worked fine during the recording periods last year (only recording acoustic events over the threshold), but the very small files at the end of the recording periods (only a couple of kB in some cases) is a new phenomenon for me. We are using Ansmann 2850mAh NiMH batteries and Transcend S300 SD cards with 256GB. I had a look at the WAV comments: The reason for stopping recording early really was the low voltage. I also tested the batteries, which were weaker or even completely dead in the cases where the recordings were shorter than expected (or there were no recordings at all). A colleague doing a similar recording task noted drained batteries after 2-3 days of recording for only one hour. At the moment, I suspect that we are using the wrong type of battery. On the AM battery case it says 1.5V and we are using 1.2V batteries. Interestingly, in some cases, the comments said "low voltage" when the voltage was at maybe 3.8V while other devices continued working at that voltage. The rated capacity of 2850mAh is multiples of what the AMs would need in our setup, so that shouldn't be the problem? Maybe the voltage was enough last year, but now that the batteries are already a bit older, the voltage output starts to drop? Thanks again and best regards!

Thanks for the response! We chose the amplitude threshold consciously and it worked fine during the recording periods last year (only recording acoustic events over the threshold), but the very small files at the end of the recording periods (only a couple of kB in some cases) is a new phenomenon for me. We are using Ansmann 2850mAh NiMH batteries and Transcend S300 SD cards with 256GB. I had a look at the WAV comments: The reason for stopping recording early really was the low voltage. I also tested the batteries, which were weaker or even completely dead in the cases where the recordings were shorter than expected (or there were no recordings at all). A colleague doing a similar recording task noted drained batteries after 2-3 days of recording for only one hour. At the moment, I suspect that we are using the wrong type of battery. On the AM battery case it says 1.5V and we are using 1.2V batteries. Interestingly, in some cases, the comments said "low voltage" when the voltage was at maybe 3.8V while other devices continued working at that voltage. The rated capacity of 2850mAh is multiples of what the AMs would need in our setup, so that shouldn't be the problem? Maybe the voltage was enough last year, but now that the batteries are already a bit older, the voltage output starts to drop? Thanks again and best regards!