norcold de-704

Hi, I own a 1990 sundancer 330 for the past 6 years. I used to be able to go for long week-ends, up to 3 days, with my 2 batteries+1 to start the engine. But as of last year, I could only stay out for about 24-30 hours and my batteries would be drained. My batteries are less than 3 yrs old and...