I have extensive experience with radar trailers, primarily from Stalker and Decatur, as I was in law enforcement for nearly a decade and spent most of that as a motor (motorcycle cop, aka traffic division). The trailers are often auctioned off when either the electronics for the radar and display systems begin to fail or when the battery systems begin to fail.
The solar panels are best to be thought of as a trickle charger, the required power for the radar, sign board and data logging (yes they do that, but typically basic information to chart speeds over times for enforcement direction) electronics is very minor.
Most of the trailers are very light gauge, to the point that I could pick side of the trailers up off the ground with ease, even with the electronics and batteries on board. The axles are similarly very light duty. Most have light duty leaf springs no suspension as it isn't typically needed due to the light weight to be pulled across town by a Crown Vic.
Point being I wouldn't put more than 200-300lbs on one, even then it might be too much for the trailer. Brand new and fully operational with electronics and batteries I would place the total trailer weight at or below 500lbs. To the point we used to use a chain and padlock our trailers to light poles because people kept flipping them over as a prank.
