Volkswagen solar panels

I don't know if they still come with these, but I have 3 small solar panels that used to come with new Volkswagen cars. They use suction cups to hang on the inside of the windshield and have a OBD2 outlet on the end of the wire that comes from the panel. I believe they have a blocking diode also (there is a small plastic box inline from the panel
I dont have any specs on these things and would appreciate any info I can get. I would like to use them for keeping small equipment batteries charged during the winter etc...