Does your car have lights for the mirrors on the sunvisor. I had a problem with the lights not turning off and the car would die in a day without driving. Hard to notice in the day light. Look in the car at night for a glow coming from top side of the visors, leave the visors up while you are looking. Also check the trunk light, easy way to do this is leave the back seats down. Even a small light bulb can drain a new battery overnight.
Hope that helps.
