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Using rechargeable lithium ion batteries?

I'm wondering if AudioMoths will accept rechargeable lithium ion batteries and if anyone has tried using them already? I'm curious how long they last compared to NiMH rechargeable or regular lithium ion batteries. Thanks!

18 comments

18 Comments

Alex Rogers

Oct 14, 2021

Yes, small rechargeable Li-Ion batteries (commonly now LiPo batteries) work really well with AudioMoth. They spend most of their life at a voltage between 4.2 and 3.7V which matches well with AudioMoth’s requirements so you get the full capacity from them. Both the AudioMoth Dev and uMoth boards have JST-PH connectors so you can typically buy a LiPo battery with the correct connector and plug in straight into these boards. There is no standard on the polarity of the connectors and the development board and radio controlled car communities typically use opposite polarities. It’s easy to swap the wires over on the connector though with a small screwdriver to lift up the plastic tab that holds the crimped wire in place. We use these batteries with AudioMoth Dev for short deployments.

https://www.adafruit.com/product/258

Alex Rogers

Sep 22

Replying to

The supply voltage to the microcontroller and SD card is regulated to 3V. However, SD card write currents can peak at 100mA and you then normally see a drop in the battery voltage due to their internal resistance. When the batteries are depleted, the internal resistance is higher and the supply voltage will drop below 3.0V. We stop recordings when it goes below 2.8V.

The regulator is effectively just a voltage controlled resistor so excess voltage is turned into heat. If the supply voltage is too high it gets too hot. Any input voltage from 3.3V to 6.0V works okay. The upper voltage is limited by the temperature of the regulator, and lower voltage by the minimum 0.3V voltage drop across the regulator.

A single Li-Ion and three series NiMH batteries spend most of their time around 3.7V and work well. As do three series alkaline batteries which start at a higher voltage but show a more continuous voltage drop over their lifetime.

Edited