I wanted to try using an external powerbank to overcome disposing of hundreds of AA batteries. I have tried a 5V powerbank supplied by RS (link at bottom of message). This is a reasonably compact size (101*66*16) and so far has powered an Audiomoth for multiple nights of recording without any power down/sleep problems. The only slight issue is some interference on the recordings, visible as faint lines every 500Hz (sample rate = 32kHz, medium gain).
I have tried three different USB cables and all show the same effect. I've confirmed this is not due to external soruces (lines are absent when using 3 AA batteries in same recording location).
This is probably bearable for my uses but does anyone know:
whether it is possible to overcome this;
whether its possible to be confident that these artefacts won't be any worse if I bulk buy more of the same powerbanks.
thanks for help
Link to RS power bank
The recording quality will depend on how smooth the 5V supply from the power pack is. Some will be better than others but it should depend on the design rather than the individual devices.
An alternative is to use a Li-Ion battery pack like these - https://coolcomponents.co.uk/products/lithium-polymer-battery-2000mah - with an associated charger https://coolcomponents.co.uk/products/lipo-charger-basic-mini-usb.
You can solder a cable with a JST connector in parallel with the existing battery pack or remove the battery pack and use the board alone.
Any battery voltage up to 20V is fine to use. The minimum battery voltage is about 3.6 (although it the AudioMoth and the SD card will typically carry on working down to about 3.1V). Li-Ion are pretty good in this respect. They go from 4.2V when fully charged to 3.7V when pretty much completely used up. We don't use them as the batteries can not be easily put through the post so it makes distributing devices trickier.