Chrysler Voyager 2.5 CRD SE

Lovely car, loads of space and fantastic for family trips and transporting big items. It looks great and drives very well when its starts! Only problem is the reliability..... Ive had a problem with the battery draining overnight. Ive had t to several garages who say they had checked on the machine and nothing is draining the battery but it still doesnt start in the mornings. Ive replaced the battery 3 times and it works great for the first month or so then I have a problem with the battery. Also expensive to run and tax, insure etc.