Battery woes
It seems my battle with battery life continues. Right now we are out of the field and I wanted to take the opportunity to test out some different options. We just ran a test of three different brand new batteries: energizer lithium, enloop rechargables, and amazon basics rechargeables. We did two deployments of each. Our recording schedule was projected to consume 24 mAh/day. All 6 units started with a voltage of >3.9. After 15-22 days all but 1 lithum unit had failed. When plugged in, the 5 failed units registered as having a voltage of 3.6. This was different than the last recorded voltage, which ranged from 3.0-3.5, depending on the unit. All units are using SanDisk Ultra 32gb mini sd cards. All units were deployed indoors, unhoused. What could be causing these units to fail so fast? The batteries were brand new, purchased within the last couple months. I'm stumped.
Hi Kaeli, The problem is almost certainly the SD cards. The energy consumption of the SD cards can vary significantly between different makes and models and we don't recommend SanDisk Ultra cards. Make sure that you have the most up-to-date firmware, and use a SanDisk Extreme 32GB or 64GB card, or one of the larger cards tested here: https://github.com/OpenAcousticDevices/Application-Notes/blob/master/A_Comparison_of_SD_Card_Energy_Consumption/A_Comparison_of_SD_Card_Energy_Consumption.pdf The battery voltage you measure after recovery won't really be representative of the voltage seen by the AudioMoth as it will recover a little after the recordings stopped. The AudioMoth reports the battery voltage measured under a light load when it wakes up to start the recording, and then also continues to measure the supply voltage to the processor during the SD card writes when the battery is under load. These voltages are typically lower, and will trigger the AudioMoth to stop the recording if the voltage drops too low. If you use the 'Summarise AudioMoth Files' option under the 'Process' menu in the Config App you'll get a CSV file including the battery voltage that can be plotted. Alex