I don't know if this will help, but I had the same problem and solved it. OK - I would start the bus and I'd have a flat battery. Called RAC - they started it and checked the battery, which they said was fine. (It was the original battery). This continued without warning, it would start first turn, I'd drive, park...find I had a dead battery. Got to know the local RAC boys really well. Every few days I'd remove the battery and put it on charge - did bugger all good. Decided there must be a drain on the battery. Some septic Chrysler sites claimed the radio amp drains the battery. So I bought a 'Negative Battery Post Switch' - a Green thing that when turned isolates the battery (clever me...there would be no drain and a quick twist was all I had to do). Still kept getting a flat battery. So I replaced the battery with a Yuasa silver 5000 YBX5096 (80Ah), cost me £95 delivered Just squeezes in - the terminals/posts are on the wrong side...but the leads just (and I mean just) reach. Problem solved...12 months later and it still starts every time. Well almost. 3 times now I've turned the key and nothing. Just as if the battery was flat, lifted the lid and the 'charged' green light on the battery says all is fine. Quick disconnect of the battery (still have the Green isolator on the terminal, too lazy to remove it) there's a click and the car starts first time. Hope that helps someone.