You need a solar controller to change the voltage to what the battery needs to recharge. You need to know how much daytime load you will have and how much battery you need to have to determine how many panels, what size controller to operate and how much battery amperage. In short, you need to start with what you want your batteries to do and then decide on how much solar to keep them going. Do some research and thinking before you buy.
try reading this article then look for more information on your specific needs.
https://roadslesstraveled.us/rv-solar/