Bat Detector Solar Solution
Why your bat detector runs out of power
Under most circumstances with proper trigger sensitivity settings, the Pettersson D500x records "mostly" bat calls and can run over a month on D-sized batteries.
But there are situations where the ambient ultrasound overlaps with bat calls, and the detector ends up recording undesirable noise. This can be mitigated first with more aggressive settings, but at some point those settings prevent some bat calls from being recorded. The next step is to add larger memory cards. 128 GB can be installed, but frankly is an insane amount of memory needed for normal summer commuting bat activity, with typical deployments really only requiring a small fraction of that capacity.
Adding a large memory capacity, in a noisy environment, will set up the situation where the detector literally runs constantly all night, ultimately leading to a power failure. Instead of a month of run time, the D500x may only run ~5 nights. If rechargeable batteries are used, the run time is typically shorter, and more issues arise due to some rechargeables having less voltage output, leading to nightly monitoring interruptions.
How to add solar to your bat detector
Short of plugging detectors into a wall outlet or hauling around larger capacity batteries, we have discovered a solar solution originally designed for cellular trail cameras which is easily modified to operate a Pettersson D500x. It is about $150 to upgrade each detector. These are the items required: