I have been getting a weird smell in he cabin off and on that I couldn't explain. today the smell just got really strong and I pulled over and investigated fully. people passing me by probably thought me weird sniffing around LOL!

I removed the back seat and was greeted to the full odor and visible fumes comming from the battery. the battery was VERY hot to touch. one call to my Bimmer mech confirmed I should change it right away.

how close to catastrophy was I?

Was it connected to the vent tube? Any battery enclosed should ALWAYS be vented to the exterior of the car. Make sure your new one is.

http://memimage.cardomain.net/member_images/7/web/739000-739999/739005_79_full.jpg

well the reason I was smelling all those fumes was because the PO removed the vent tube when he/she changed the battery!!!! WTF?!?

looks like it :confused