Directly output from the solar panel that's pretty normal voltage. You need to put a solar charge controller between the solar panel and 12v
system in the trailer. It steps down the voltage from the panel to the necessary voltage for 12v
load and battery charging. Since it's just a 20w panel you'll be able to get a basic one fairly cheap.
Just reread, is it a integrated all in one solar battery charger and not just a solar panel. If so that may be normal for its operation when not connected to a battery. Indicating a no load voltage output. Connect to battery and see how it functions once the battery is fully charged.