I am having a recurring issue where my Audiomoths are stopping recording after only 60 hours at 48kHz. I believe it may be associated with the Enable low-voltage cut-off : Yes setting. Previously you could turn this off in the config, but now it is no longer an option? Below are two deployments with identical batteries, SD cards and configurations. Energiser Pro Max Plus Batteries, Sandisk Extreme 64GB cards. One records for only 58 hours, the other for 166 hours (the amount of time I would expect). This issue happened to me on almost 60 recorders in my last deployment, and I decided it must have been a bad batch of batteries (was using Varta) so I swapped to Energiser Pro Max Plus and the issue still persists. Any ideas why? Summary files and config attached. The early stoppage seems to occur when the battery drops to 3.5v, but this is happening far earlier than it should right? v1.2 Audiomoths. Previously have had no issues getting 160-180 hours out of normal alkaline batteries. Any advice appreciated, thank you!
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Edited: Sep 19
Same config, same batteries, same SD, vastly different recording times? Audiomoth stopping recording after approx. 60 hours regular issue
Same config, same batteries, same SD, vastly different recording times? Audiomoth stopping recording after approx. 60 hours regular issue
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Hey Alex and Callan, I currently have 50 audiomoth deviced deployed and just took in the 3 first ones to check. They all have the same settings, 2 of them worked fine, one of them stopped writing files after 60h of good recordings. It still wrote 5 files after, but they are empty. The one with the problem has a SanDisk Extreme 64Gb from Taiwan, the other two are a SanDisk Extreme 64Gb and a SanDisk Pro 64Gb both from China. I will go to the fieldsite tomorrow and check all of them for errors. Also I set them without any sleep duration, so the writing error might also due to that and the card is just a coincidence. Please let me know if you have any updates!
I’ll get some SanDisk Extreme PLUS cards to test. SanDisk Extreme Pro cards had very high write currents and generated noise in our tests. We generally only use regular SanDisk Extreme cards.
Hi,
I don't think this is a firmware issue. We removed the option to disable the low-voltage cutoff as some people were experiencing damage to the SD card when they ran the battery down very low without it enabled. The low-voltage cutoff is implemented by measuring the supply voltage to the microcontroller and is set to 2.8V. The supply voltage typically drops below this during SD card write operations with heavily depleted batteries.
In this case, the final recordings experienced SD card write errors that prevented them from being closed, indicating that in both cases the supply voltage probably was quite low.
The battery voltage measurement is made before the recording starts with a battery that is quite lightly loaded. The full recording shows a typical profile for an alkaline battery. The early stop recording is very different. The second recording each day shows a much lower battery voltage despite the higher temperature later in the morning. This looks like a depleted high internal resistance battery. Another possibility is the SD card. This is often where variation between expected and actual deployment lifetime comes from. However, if these are all SanDisk Extreme cards I would think this less likely. Double-check the cards to make sure they all look genuine though - there are fake cards in circulation which have poorly printed labels. The fact that there is such a difference in battery voltage between the first and second recording makes me suspect the batteries though. It would be good to try the setup with a more energy-intensive profile - making 55-second recordings with 5-second sleep periods between them at 384kHz - so that you can reproduce this much more quickly on the bench. I would imagine that you should see the difference within a few hours. If you have a good digital multimedia you should be able to measure the current being drawn by the AudioMoth whilst making recordings. If you set a 200mA scale, and switch to DEFAULT, it will make a continuous recording and you will see the average consumption. You can double-check for differences between the AudioMoth and between the SD cards.
The set-up above is supplying 4.0V through a digital multimeter. Average consumption whilst recording at 48kHz is about 14.5mA as expected.
Whilst waiting between recordings the energy consumption will be about 100uA on average with a maximum close to 1mA each time the LED flash.
Or if you can ship one of the devices to andy@openacousticdevices.info, he can check it.
Alex