solar panel install

I want to permanently install a solar panel in my Subaru Baja. I have a VW panel that is designed to keep new cars charged during shipping. It just plugs into the cig. lighter. I'll ditch the plug and wire it in up elsewhere (after making sure it's diode isn't in the plug somewhere). It seems simple enough to ground the ground and plug + into a circuit that is always +12v, but I wanted to make sure that's not a bad idea. Isn't that all the cig. lighter plug is doing? If that sounds good I'll wire it up, disconnect the battery and check for 12V on the battery terminals. Thanks!

The way you described should work fine to keep the battery topped off. The panel will not put out current to cook your battery. Good luck, Tom