My wife got stuck today going to work - she shut off her X5 and it would not start. Roadside Assistance did some troubleshooting with her and said to tow it. The dealership said it was a battery and I decided I wasn't going to pay the $300+ for a BMW battery.

Tonight I replaced it myself with a Wal-Mart battery and took it out for some errands. While parking it the garage I noticed battery acid leaking from the back of the car on my garage floor! Not good...

Does it sound like I could have cracked the casing while tightening the hold-down bracket (I do not think I overtightened it) or does it sound like maybe my electrical system is overcharging the battery and caused it to boil over? I did make sure to connect my vent tube - but that should only vent gases and not leak at that area. Won't know any more until the morning...

Anyone else with such a bad battery experience?