One of the reviews on Amazon mentioned...
"I originally gave this product 3-Stars. After using it on three RV Journeys I have lowered my opinion of this product. The Power Defender is not rain resistance. A couple of thundershowers caused water to enter the component. A small amount of rain residue in the component caused the electrical wiring to short out. It will give false indications of voltage problems and chatter."
https://www.amazon.com/Camco-PowerDefender-Integrated-Protection-55310/dp/B00JGJH8QU
That said the Q&A on Amazon also mentions...
"The Power Defender Voltage Protector provides three functions. It monitors the voltage level of the power source and will disconnect power to the RV if there is an unsafe high or low voltage and automatically reconnects power once the voltage has maintained a safe operating range for two minutes."
These are features you do want in a surge protection device but the water resistance issue would be a major issue given these things are subject to rain, wind, etc.