X3 Battery Problems

I had a problem with my wifes 2005 X3 tht I thought I would pass along. About a year ago, I replaced the original battery. A month or two ago, we encountered a situation where when turning the ignition key to the "start" position, nothing happened. Everything else seemed perfectly normal.

After this happened several times, I looked at the battery & discovered that the positive terminal was loose. I tightened it, everything began to work perfectly again for a couple of weeks, when the problem returned. When I looked closer, what had happened was that the terminal was not quite pushed all of the way down on the terminal. Since there is taper in the terminal and on the battery post and the terminal not being fully down combined to cause the terminal clamping mechanism to bottom out before fully clamping the terminal.

This problem is made worse because of the long arm on the terminal back to the cable. This causes a lot of leverage on the connection everytime the car goes over a bump & eventually, the clamp walks it's way up the terminal.

In hindsight, this all seems obvious, but reading all of the posts of battery issues on X3s after replacing batteries makes me think I may not be the only one.

Originally Posted by timarnold

In hindsight, this all seems obvious, but reading all of the posts of battery issues on X3s after replacing batteries makes me think I may not be the only one.

Yes, there have been one or two reports of aftermarket batteries where the X3's terminal does not mate properly with a battery post.

This one is the opposite of what you found, the negative post being too slim:

http://www.bimmerfest.com/forums/sho...0&postcount=19

That's easier to fix than a post being too fat as you found.

Something to watch out for when fitting a replacement battery, and a bit of modification might be needed with a file or something.

Not sure if there are different post size standards or it's just poor manufacturing tolerances.

Or maybe this just occurs with the Group size 49 and the H6 and H8 size batteries are O.K.?

If I was to make a guess, I would guess that the taper angle is actually the problem. It would be a lot harder to properly clamp up on mismatched tapers.