B+ motorhomes

Hello all, I have a 2007 Holiday Rambler Agusta Sport with the Chevy engine. This past winter the battery went dead a few times and had to get a boost to get it started. I figured I wait till spring to get a new one. I went to R&S Strauss and bought a new one, from the moment I installed it and started the RV I new something was not right because my rear camera wouldn't turn on. The power light on it was on but no picture. And the battery gauge on the dash seemed to be lower then what I remembered with the old battery. 2 days later when I went to move the RV it wouldn't start, gave it a boost and it started right up. If the RV goes 1 day without being started the battery goes dead. I know nothing about car (RV) engines and what makes them work. I gave the salesperson the details about the type of engine I had and they gave me a battery that looked like the old one. Can someone kindly guide me in the right direction?