Mitsubishi Repair: 2003 mitsubishi diamante battery problem, 2003 mitsubishi diamante, mitsubishi diamante

Question
Six months after purchasing my 2003 Diamante (new) the battery died. Dealer checked everything, no problem found. About 8 months later it died again. Dealer ran checks and found nothing but agreed to replace the battery. About 1 year later the battery died again (cold weather this time). It died again 12/06/07 and I replaced the battery 12/07/06. It just died after sitting for two days (03/14/08) in about 30 degree weather. I am using Interstate MT-86 batteries, which came with the car when it was new. Any ideas as to what could be killing these batteries ?  Would changing to Optima batteries help, the car has 56K on it and is too new to replace.
Ray

Answer
Ray: Gee I got to say your dealership does not sound very much with it. Sorry, but there is either a short someplace, the alternator is not doing its job as to keep the battery charged up, the cables on the battery are bad, loose, broken or faulty wiring in the charging circuit, a short in the car's wiring. The belt that drives the alternator is not working right, slipping, needs replacement these are all ideas from my repair manual. You need to take the car to another shop, you know like when you are sick and a doctor tell you something; it is always better to get a second doctor to either agree with the first or tell you something else. So it better to get that car into a another shop and see what they you. Hope this helps you and God bless: Linda