The Pettersson D500x uses
either AA or C type batteries, depending on the manufacture date.
Unfortunately, due to the high number of variables (record time and length,
sensitivity settings, screen brightness, nightly bat activity, insect noise, humidity,
temperature, etc.), it’s difficult to give an all-inclusive estimate of battery
life. Due to these factors, this timeframe can range anywhere from a few days,
to well over a week. However, we generally recommend checking your detector at
regular intervals to keep an eye on remaining battery life.  Advice that we find most useful: Don’t leave
your detector unattended any longer than you can afford to lose data!