I have a 1995 850 with just over 100K miles. It appears to be eating batteries, and I'm worried that there's an intermittent short. Does anyone know of any likely culprits on this model?

Here's the background:

The car's garaged in San Francisco--no cold weather. I've had it since 1998, put on 80 miles a day for two years, but since 2000 it has been driven only about once a week. At the beginning of 2005, the battery was 2 years old and had been installed by my shop. The car has had only one electrical-related problem--the gas cover lock had stuck shut, and a new latch motor was installed in early November 2004.

In mid-January 2005, I went to start it and the battery was dead. I had it jumped, it started right up, but a week later it was dead again. I jumped it again--same thing. I took it into the shop in mid-February, and they couldn't find anything that would be draining the battery, and we just concluded that the infrequent use had been hard on the two-year-old battery, and we replaced it.

By the beginning of April, the new battery was dead. I took it back to the shop, and they still couldn't find anything that would drain the battery. So either we got a bad battery that wouldn't hold a charge after just 6 weeks (unlikely), or there's an intermittent short. If anyone has any suggestions, I'd really appreciate your help. Thanks!

Ed Batista