Originally Posted by Weasel

1, maybe not use all caps next time, it looks like you are yelling at people.

2, I'd hook up that vent if I were you! When a battery is "working" it vents corrosive gasses... and that isn't good to have in the cabin of the vehicle right by all the electronics. BMW engineers were smart enough to put a vent hose there to redirect the gasses outside the vehicle. I have 3 times in my career at BMW seen electrical problems caused by the vent not being used with aftermarket batteries. Usually on a car model where the battery is right under the rear fuse box, and guess what, that fuse box got severely corroded and needed to be replaced along with some wiring. Expensive job....

And that was actually made worse by the aftermarket battery believe it or not... these vehicles charging systems are computer controlled. So if the OEM battery has 850 CA, 850 CCA, 110AH and 250 RC. and the aftermarket battery has 950 CA it must be better right? Not exactly... that 950 CA battery has only 750 CCA, 90 AH and no listed RC rating. So when the alternator is trying to force more charging amps down it's throat than it is designed to handle it produces more gasses as a result.

I'm not telling you not to use the aftermarket battery, just that you really should hook up the vent hose to prevent costing you electronics. (the self leveling suspension module, PDC, radio if you have nav, trailer module if you have towing, etc. are all right by the battery)