we recently bought the Grand Design 303 RLS and bought without battery. I added and aluminum angle in the bottom center ish at the hole, put in two Group 29 lead acid batteries as that configuration has worked for our application well for over 16 plus years. they are covered with a simple storage container turned over with the original venting attached. You might be able to take the battery back to the selling dealer and get some type of credit and spend the $$$ in their store. Always worth an asking! Good Luck & Be Safe ! ! !