OK. Follow up.
I couldn't find what I considered an acceptable solution to the weatherproof charge controller question, so I decided to go a different route. I have had one 90w solar panel on the roof since I originally took delivery of the trailer. I decided to add a second 90 watt solar panel to try to increase charging.
To reduce voltage drop, I wanted to put the solar panels in series. The PWM controller that the Airstream dealer installed won't handle two panels in series, so I bought a Victron SmartSolar 100/30 to replace it.
I opened the trailer up to replace the controller only to find the dealer had mis-wired the system. He had wired the controller exactly as he should, BUT, this controller forces you to connect the PV negative wire to the battery negative. The dealer had hooked my PV negative wire to the battery POSITIVE. Both of the PV wires were hooked to the battery positive, giving a dead short. I was getting NO charge from the solar. No wonder I was unhappy.
Since I had the Victron, I went ahead and removed the dealer's PWM controller and installed the Victron. Correctly, this time.
I ordered the second solar panel before opening up the trailer. It is not here yet, but I will go ahead and install it. I will see how getting NO charging improves with 180w of solar, CORRECTLY installed, before I think about portable panels again.
