Hello! I just retrieved 23 AudioMoths (all v. 1.2.0, firmware 1.8.1, SanDisk Ultra 64GB micro SD cards, and Energizer Max or Max Plus batteries) from the field. Unfortunately, 18/23 devices had red and green SD card error lights. The SD cards won't register on any computers (I haven't tried card recovery software yet). Most of the cards were brand new, all were exFAT formatted and tested before deployment.
These AudioMoths were already in the field, where I replaced the batteries in July and used a laptop and the config app to set the time and configuration again. What could have gone wrong here? Is there any way to save the cards? Thanks so much.
Edit: I have just checked other cards in a couple of the devices and they are recording fine.
Hi Emma, Can you confirm what sample rate you were using and what the recording schedule being used was? It sounds like the batteries may have run down and the low voltage as damaged the SD cards in some way. We've had a few reports of this recently and have just released an update to version 1.8.2 which cancels the recording schedule after 5 failed attempts to write to the SD card. Some people have also experienced problems with SD cards that are removed from the AudioMoth whilst writing, rather than switching to USB/OFF first, but I don't think that is the issue here. In general, we don't recommend SanDisk Ultra cards as they are too slow for high sample rates and have very high peak currents. The SanDisk Extreme (red and gold) card is the one that we recommend to users.
Can you check the files on the readable SD cards. If the battery was running down and affecting recordings, the recordings will get shorter toward the end (and the comment in the WAV file will say that the file is short for this reason), and there may be a number of zero length files at the end. The data should be recoverable from the SD cards as it seems that it is often just the file allocation table that is corrupted. However, we haven't actually experienced this ourselves or seen an SD card from such a device to be sure.
Alex