91 735il remove power rear seats

On Friday I used my '91 735il to jump my wifes car. On Saturday I drove to Atlantic City and drove home Saturday night. On Sunday I watched the game. On Monday the car was dead. I jumped the car and drove to the store Monday night. It ran fine and no problems. I came out of the store and it was dead. Wife came, I jumped it and all was fine, no dim lights, no fluctuation with engine revs, all seemed fine. let it run with no lights or other drains. Turned the key off, then tried to start, NOTHING!!!
Any thoughts on the problem, I figure, Ill start with replacing the battery, but I have power rear seats and they dont just pop off. There is a 1.5"x4" pop off cover that opens to reveal a 1/2' bolt head. Is this related to seat removal? HELP!

Jon Evans has a good write up on the subject of the rear power seats:

http://evansweb.info/article.php?story=20030118230556915

The battery has quite a hard life with these cars, and one in good condition is imperative.