Those 5W and 10W solar things are a waste of time, space, and money. They don't put enough back into the battery to keep up with natural self-discharge unless they're in full desert sun with 100% exposure from dawn to dusk. If you've got it propped up in the windshield on the dashboard, you're only getting a fraction of its output.
What you're seeing now is just that the detector draw is almost negligible, as it should be.
I wouldn't leave it for weeks on end, though. When I park mine, the camper umbilical gets unplugged and/or the camper's shore power gets plugged in.
Any kids know what's good for them if they mess with the cord, and they know that getting electrocuted is the less painful of the two options.
