When I started using AudioMoths, I knew next to nothing about bats and probably still don't know much :) I use the following settings Recording Tab Recording TabSample Rate set to 192, in order to be able to include the whole range of Pipistrelle Sounds. Gain slightly enhanced Sleep Duration set to 5 secs - because Audiomoth seems to need that, regardless of how long the recording period is. Recording Duration set to 25 (or fifteen) so that I get 2 or 3 files per minute of recording time. I know that 5 secs is generally thought to be sufficient, but I like to be able to see visually the entire call sequence in a sound editor (I use Audacity) I like to record a period that extends a little outside normal dusk and dawn. THis is what I have set currently. I'm using Energizer recargeable batteries which seem to last about 3 days (4 max), so I regularly change the batteries and the exact times used for recording. For the purposes of saving space on the memory card, I use the Amplitude Trigger, I use a Minimum Trigger duration of 1 second, which I have found works best for me. I record in my garden and if I set a longer trigger, I don't capture much activity. I set the Amplitude Threshold to 5% - this is the change in volume that triggers the start of the recording. You will have to experiment with these two settings to optimise your own disk usage. I use 64GB and 128Gb cards and find that with these settings and replaceing the batteries every few days, I don't run out of space. I sometimes play about with this filter settings. For example you could use the band filter to set limits for the lower and upper ends of the frequency range that you are interested in. I am also interested in recording Birds, Mammals and any Bat species, so I tend to have the Audiomoth record across the entire range. Using the whole range maybe overkill for your needs, thats a decision that you need to make. Remember, the Sample rate on the first tab, determines the frequency range that is available. Eg setting the sample rate to 250, increases the upper limit to 125KHz. Decreasing the sample rate to 96, reduces the upper limit to 48KHz. Another key consideration in using Triggers is that, when enabled, the AudioMoth generates T.WAV files rather than just .WAV. These are more compact on the microSD card, enabling you to record more data but should be 'expanded' before use., once you have transferred them to your PC . It might be worthwhile buying a large portable hard drive (5TB or so) as you will generate a lot of data and if you want to retain all your data collected, you will need a lot of disk space. I always tick the box 'Use daily folder for generated WAV files', so that the files for each day are collected together in separate folders on the microSD card. I also enable the energy saver, though I haven't noticed much benefot from using it. With these settings I regularly pick up 3 pipistrelle species, Noctule etc. I use BatClassify to scan the generated files, then take the files with the best scores (i.e. greater than 75% accuracy) and upload them to the BTO Acoustic Pipeline website for analysis. I find that the results generated for the Pipistrelle and Noctule species are pretty accurate. I've not had enough experience recording the other Bat species in the UK, to get a real feel for the accuracy of the analysis for those species. [If I have posted any misleading nonsense above, I'm happy to be corrected. I'm learning all the time]

As Alex Rogers has already said, The BTO's Acoustic Pipeline tool is very effective for Bats & small Mammals. However, before uploading my recordings, I run BatClassify against the files (I generally set the time length to 15 secs) and it is fairly accurate in identifying the files containing Bat Sounds. The results are presented as a .csv file which I take into Excel and then I use a formula to determine which are worth uploading (from hours and hours of practical experience only those files with a score over 80% are worth processing further). https://bitbucket.org/chrisscott/batclassify/downloads/ When uploading Bat recordings, the Acoustic Pipeline tool will identify that a Bird is present but will not identify the species. It is however pretty good for Bats and small mammals, though I usually visually check the files for unexpected species, once I've received the results of the analysis. Some of the regional Bat groups in the UK have done their own studies on the accuracy of the various recording tools and analysis software for bats. There are separate services available via the Acoustic Pipeline upload tool, which focus mainly on nocturnal birds - either nocturnal breeding birds (Owls, Nightjars etc) or Nocturnal migrating birds (Thrushes, waterfowl etc). I have been mainly selecting these files visually, but have not yet found a bird equivalent of Bat Classify, to help simplify that process. Acoustic Pipeline gives you 100Gb upload limit per year for free. If you need more than that, that you can buy extra units.

I've just had a delivery (in the UK) this morning of a strip of 10 mic jacks from Mouser

This sounds like what has happened to 3 or my 5 devices. I was thinking that adding an external microphone might fix the problem and am intending to try that (even though I haven't used a soldering iron in years)

Thanks @Alex Rogers for the handy explaination of some of these settings. I'm fairly new to the bat recording lark and I've been stumbling around in the dark a bit myself, so this is really useful. I have managed to capture some bat calls (only really Common Pipistrelle, so far) - but once I've gotten the hang of the settings, I intend to make recordings away from the back garden. I've been uploading my recordings to the BTO Acoustic Pipeline, for automated processing with some success - as hacking about with hours of recordings in Audacity is taking up way too much of my time. The Acoustic Pipeline can identify 24 species of European bat, plus small mammals and some insects and can be found here https://app.bto.org/acoustic-pipeline/public/login.jsp

Thanks Alex. I think that I have got the hang of things now. I did see a repeat of the above behaviou on another evening, where the initial recordings were of the correct length and then there were further recordings of various lengths until the rechargeable batteries gave out. I agree with your analysis that the behaviour is consistent with the batteries needing to be recharged. I have now purchased some new rechargeable batteries and the Audiomoth is producing files of the anticipated length and size, providing I keep the batteries charged up. Thanks very much for taking the time to answer my query. 😀

OK, so having put this down in writing, I played around with the configuration and noticed that when I increase the sample rate, the frequency range that I can filter on, increases. Apologies if this was evident to other users, but it certainly wasn't to me ... and my physics degree was a long time ago. Doh! So that kinda answers my question on how I could use the AudioMoth to record Bat sounds. On the SD Card page of the 'Getting Started' section, I read this: From AudioMoth firmware version 1.2.2 onwards both FAT32 and exFAT file formats are fully supported. However, if you are using an earlier version of the AudioMoth firmware ensure that your SD card is reformatted as a MS-DOS (FAT32) card prior to use, or reflash you AudioMoth to use the newer firmware (see instructions here). As I have a new Audiomoth and Firmware version 1.5.0, I guess that my device can support cards formatted with exFAT and I presume also that this means that the 32GB card limit is also removed as I'm using a 64Gb card and at least managed to get some recordings generated. Re-configuring and putting the device out in the garden for another spin.