Yep, we had a Buick one time that if you drove it every day you were ok, but if it sat over a weekend the battery was dead Monday morning. My ex-wife LOVED when that happened and she was going to work. We finally tracked it down to a bad alternator. I think the diode was letting current feed back through it and draining the battery just slightly. We replaced the alternator, no more problem. Have it checked out.

You can also remove your negative battery cable and put a test light between the post and the removed cable end. If the light glows at all you have something pulling current. You might get a faint glow from the memory in your radio, but if it is still on you can start pulling fuses until you find the offending accessory.

Don