I have a 2005 Ford Mustang. I haven't been driving it everyday and after about a day or so, it wouldn't start. I bought a new battery and we installed that. But, the battery wouldn't stay charged. The cd player was doing some funny stuff even if I didn't mess with it. We took out the radio fuse and that seems to have been the problem. What is a good replacement battery? I'm not looking to spend a fortune, but I want something nice.