I powered it from the lighter, so I could install a hidden microswitch to switch it off sneaky. Here, the use of radar detectors is not allowed:
https://photos.app.goo.gl/sSHE3DRo9RPnvCyu8
https://photos.app.goo.gl/yyESWHc3LqUV8f687
https://photos.app.goo.gl/TCDLye16pyVC1G6D8