Dear all,
According to https://www.openacousticdevices.info/sd-card-guide, the recommended microSD cards for most deployments are the fast U3/V30 cards, in particular SanDisk Extreme (either HC-I for 32GB or XC for > 32GB). However, our field data shows that a slower U1/V10 model card consumes batteries more slowly. We are trying to understand this contradiction.
We are using audiomoth firmware basic version 1.11.0 (date released 19/11/2024) with WAV recording. Recording schedule 180 minutes, from 60 minutes before sunset to 120 minutes after sunset. Each record produces a single file one minute long. Recording duration 55 seconds. Sleep duration 5 seconds. Daily energy consumption is approximately 34 mAh, according to the audiomoth configuration app. Sample rate is at 32kHz and gain is set at medium. We enable sleep/record cyclic recording. We use daily folders for the generated WAV files.
We have 22 recorders deployed in a local environment (the maximum distance between recorders is approximately 50 km, with negligible differences in altitude), and we worked for almost the same period of days with the same brand and batch of alkaline batteries (Energizer Max). Temperatures during this period were above 0°C.
We found that audiomoths equipped with U1/V10 microSD cards (Kingston Canvas Select Plus 64GB, U1, V10, A2) were still recording after 32 days of operation, while those equipped with U3/V30 cards (SandDisk Extreme 64GB U3, V30, A2) drained their batteries sooner and stopped working in about 21 days. This is about a third of what would be expected from the daily power consumption indicated by the Config application. I extracted the daily average voltage and temperature from the metadata of the wav files belonging to only two randomly selected recorders to plot voltage versus date (see figure). It clearly shows that the slower card (U1/V10) drains the batteries more slowly.
How can that be?
It seems that U1/V10 may outperform U3/V30 for very short recordings. Would deployments with longer recordings favour U3/V30 cards in this regard? (for instance 18 10-min recordings or 36 5-min recordings, with the same total amount of 180 minutes)
Hi, Slower cards typically have lower energy consumption, although it also seems to depend a lot on model and manufacturer. The U1/V10 cards may be too slow when recording at 250 or 384kHz. AudioMoth uses an SPI interface, rather than the faster SDIO interface, so typically doesn't achieve the full speed of the card. Beyond that, the consumption of SD cards varies between manufacturers and specifications very significantly. We have found SanDisk Extreme cards to be reliable and generally have low-energy consumption. However, we've recently seen SanDisk Extreme cards manufactured in Taiwan that have much greater energy consumption (x3) compared to SanDisk Extreme cards manufactured in Malaysia and China.
https://www.openacousticdevices.info/support/device-support/same-config-same-batteries-same-sd-vastly-different-recording-times-audiomoth-stopping-recording-after-approx-60-hours-regular-issue/dl-e01891dd-8973-495d-b203-3847ee83719e?origin=notification
Can you check where your SanDisk Extreme SD cards are manufactured? It should be written in small letters on the card itself. Energy consumption during waiting periods is very small - typically 100uA including LED flashes - so you can measure average energy consumption with a meter during regular recording periods to actually see how much energy is being consumed.
Alex