kmrod

I recently purchased an 07 550i at auction. The car had been hit in the back right side. When we picked it up the battery was dead so we put the jumper on it and it started and ran well. While test driving it the gauges flickered a bit but after a few minutes seemed fine. We got back to the shop turned it off. Next day tried to start and nothing. The dash lights come on BMW displays on Nav screen. Idrive occassionally flashed on then off but car won't crank. Thought it was the battery so we installed a new battery same thing. Did some research and came up with the BST stuff. Saw the pictures and realized this car doesn't have a BST. Continued to search and while I saw the resistor mod I have yet to see a mod that allows you to remove the BST entirely. Any suggestions. Will post some pics of the battery as soon as I can get back to the shop. But any help would be awesome. By the way all the SRS lights are on.