I had to replace the battery in my Z4 M and it appears that the battery vent was not attached to the battery. The previous battery was a BMW OEM battery and was most likely replaced by the previous owner. However, the vent tube was not attached and the vent on the other end of the battery was not plugged. I've looked at other threads about replacing the battery both on this forum and another forum, but I haven't been able to find any pictures of how the vent tube is attached to the battery.
Here's a picture of the battery compartment in my car with the battery mounting frame removed to get a better look at the entire battery vent tube. The vent tube is the light gray tube which vents out to the bottom of the trunk. The open end is slightly enlarged and it appears that something was plugged into it with "ribs" which enlarged the end of the tube and left a pattern inside the tube and this part was also plugged into the battery vent hole.
Does anyone have a picture of what this connector looks like or the part number? My parts guy at the local BMW dealer says that it is just an elbow connector but didn't have one in stock so he ordered one. I tried a 1/4" elbow from my drip irrigation parts but this isn't going to work.
Whoever did the last battery replacement didn't do a very good job. I have to replace the positive battery terminal cover because both of the flaps to access the nuts were broken off.