Recording failure with 512GB SD card

Hello,

I have an issue during the recording session with the AudioMoths.

I set up a first AudioMoth (AM 3) on 19th March at 2pm. I scheduled a recording session on a 10min cycle with 4min of recording and 6min sleep for a frequency sampling of 250kHz. (see CONFIG_session1)

I did a LED check up 9 days later and I saw the green and red LEDs blinking simultaneously, so I removed the sensor and checked the SD card. I get recording files from 19th March at 2pm to 25th March 18:10. I have an empty file at 18:20 that I can't open because it is invalid or corrupted, no more recording after that. The metadata for 25th March at 18:10 indicates that the battery was 4.6V and temperature was 12.1C. (see outcome_session1)

I checked the voltage in the Config App and with the multimeter to confirm it. The battery was full, so I suspected an SD card problem.

I ran a second recording session with the same configuration after reformatting the SD card for the same sensor. (AM 3, see CONFIG_session2)

I started the second session on the 31rst March at 12:10. I added a second one AM above the previous one (AM 15) to explore the repeatability. It uses the same configuration, SD card type (also reformatted before use) and battery.

I did a LED check up today and I have the same LED error on my first sensor (AM 3). I checked the SD, I have two recording files for 31rst March at 12:10 and 12:20. The 12:30 file is empty and unreadable for the same reason as before. The metadata for the 12:10 and 12:20 display that the battery was 4.6V and temperature was 21°C at 12:10 then 19.6°C. (see outcome_session2)

The second AudioMoth (AM 15) works fine. I checked its metadata for the same recording as the AM 3. The battery level is the same with some differences in temperature: 21.5°C at 12:10, 18.5°C at 12:20 and 20.4°C at 12:30.

For your information, we use CZVV Rechargeable Li-ion Battery 2333mAh and a Samsung 512GB EvoSelect microSDXC I U3 A2 V30. We don't know if the storage memory is a factor in our problem, or if it is related to temperature/battery voltage variations, for example.

We would appreciate your help in finding the root cause of our recording error. Sincerely, Camilia

4 Comments

Alex Rogers

Apr 02

Hi Camilia, I've replied by email but it's useful to repeat it here. I think this is an issue with the batteries. These batteries contain a voltage regulator and so their voltage is not a true reflection of their state of charge. It isn't clear from the link what their capacity is, but it seems to be a lot less than a regular good quality alkaline battery, or a NiMH rechargeable battery, and they may not be able to supply the high write currents of the SD card. Alex

camilia

Apr 03

Replying to

Hello Alex,

Ok, thank you very much for your quick reply. For our protocol, the duration would be fine and we will recharge the battery before using it for a second time. We were afraid to have the issue before the end of our recording schedule.

Thank you very much.