I mistakenly procrastinated when I was doing a bunch of other, what I felt was more important engine repairs after I first bought my 633csi. One day, as I dropped from about 80 to about 30 to take a hard right, the battery launched from it's unbolted position, just about 5 inches, but enough to snap my battery cable. Fortunately, it was near my work where I could grab some tools.. but it was embarrassing sitting on the side of the road with my 6 that I'm so proud of owning and restoring, and having to fudge a hack repair to get back on the road.. Needless to say, that was the very next thing I did.. Bolt it down properly and replace the cable. Don't let this happen to you!