HydroMoth Battery life issues. Diagnosis and solutions. Wrong SD cards for the job.
I have a small army of HydroMoths deployed in the field. Upon visiting them yesterday i randomly stumble upon 2 devices with malfunction.
All devices are configured with SanDisk Extreme 128GB cards. And with brand new 3 x Energizer Ultimate Lithium AA batteries, these were bought in packages of 10 from a reputable seller and used consecutively from one package to the next. I have now retrieved both devices and i have done the "Summarize Audio Files" in the Configurator App for the two devices ID 009 and 012 Device ID 009 Summary of issue:“Recording stopped due to low-voltage behavior on 15 April 2026; later found in clock-not-set / chime-wait LED state.”
Device ID 009 has a red light constant and a blinking green light. Logs indicate a low voltage? I find this very weird as they have only been in the water for 14 days.When i plugged in the device to the Configuration App it reported 4.4V, the logs said it stopped at 3.9V. In the config i found this flag "lowVoltageCutoffEnabled: true" i have not seen this in the Configuration App. Can it be disabled? Upon testing the batteries 1 of the turned out to be in the RED (REPLACE) part of a basic Mercury analog multi battery tester. Device ID 012 Summary of issue:“Device 012 was recording correctly until 15 April, then began failing due to low voltage. The red+green synchronous blink pattern is the post-failure indicator for those cut-short recordings.” Device ID 012 has a red and green synchronous blinking with about 2 sec in between and flashing for about 100ms. When i plugged in the device to the Configuration App it reported 4.4V. Logs again indicate Low voltage. Again upon testing the batteries 1 of the turned out to be in the RED (REPLACE) part of a basic Mercury analog multi battery tester. The consequence of this is that i now have to revisit nearly 100 ponds to check batteries. My lesson learned is to never trust battery manufacturers again.
Hi Alex
I just pulled 9 more devices from the water, and they seem to all have died from Low Voltage. This confirms that the two first devices probably died from the same cause as these ones. You can download all configs and summaries here (for 3 days):
https://we.tl/t-6LZ9Z1OwJPLWZLhD
I find that they all die after about 54-58 hours or about 13-14 days it seems (13 GB ish). What I find unsettling is that of the 11 devices 7 had just one battery in the REPLACE category and 2 in GOOD. Testing using an old Mercury analog tester (4 Ohms Nominal load, >1V is GOOD/LOW and <0.9V is LOW/REPLACE) , so not top-notch accuracy but this is weird to me if they run in serial. Also the battery slots changed randomly, so no clues that point to hardware faults in the HydroMoth here.
I found signs of condensation in 1 of the devices (004).
Last year I had 9 devices survive for 55 days, they were deployed on 16 april, with SDSQXAH-064G-GN6MA cards. Something that is probably unimportant is that they were scheduled for 23:00-23:00 and this year they say 00:00-00:00. Also, this year I disabled “wait for acoustic chime) and “battery indicator”.
Otherwise, settings are identical. Hardware-wise I chose SDSQXAA-128G-GN6MA this year, which is a bad move as the device is not storage limited atm, but battery limited. Thus I may only theoretically be looking at 47 days of recording vs 55 as the 128GB cards draw more power. This alone does NOT explain why I am seeing my recording time drop to 14 days, however.
I am in the field, and my devices are supposed to be recording right now. This is catastrophic for the project.
I see 2 possible solutions to salvage the fact that I need to record at least until 15 may.
Discard the SDSQXAA-128G-GN6MA cards and all previously used battery cells. Buy SDSQXAH-064G-GN6MA cards and brand-new Ultimate Lithium batteries.
Or
Use existing 128GB cards, discard alle used batteries and buy brand-new Ultimate Lithium batteries but reconfigure with 16 kHz and/or battery-saver enabled (Settings before were 32 kHz and battery-saver disabled).
I will source the batteries, if possible, from a different vendor. But I think the most important factor here is actually the microSD card, somehow the power draw is a LOT higher that I can compute.
Br. Sprain