Excessive battery drainage on 1999 Buick Park Avenue

What would cause the battery to be dead every other day, especially in cold weather or when the vehicle has only been driven for short distances(ie to the store) and not for extended periods (longer trips like at least 30minutes hwy)? I have replaced the battery every year for the past 3 years,invested in a rechargeable battery jumper. I have also had the altinator checked as well.

Asked by for the 1999 Buick Park Avenue
It sounds like there is a drain on the battery. If this is happening consistently, then it shouldn't be too difficult to isolate the problem for an experienced technician. Have you had it looked at for this problem? I'm not talking about a battery or alternator test, I mean test for a drain on the system?
You'll need to take it to a good quality Independent repair shop or the Dealership. You need a technician who is experienced in electrical system diagnosis and preferably GM experience. These electrical systems are still simple in some ways, but they can get complex very quickly, and an inexperienced technician can create more problems rather than solve them
Your looking at a minimum of 1 hour diagnosis to start looking into this problem, and it could be more if there is a detectable drain on the battery that is difficult to locate.
Where do you get a test for a drain on the system? How much would something like that cost?