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      01-01-2010, 09:04 AM   #157
Second Lieutenant

Drives: E46 M3, E92 M3
Join Date: Sep 2009
Location: PA

iTrader: (0)

I thought that tube on the side of the battery is to divert Hydrogen rather then acid fluids.

It is common knowleage that car batteries produce a fair amount of hydrogen when being charged.
Since BMW batteries are stored in a relatively air tight place, the trunk, in order to prevent hydrogen build-up, a tube was installed to divert hydrogen gas to the exterior of the trunk.
This was done aimed to prevent explosions might be caused by static electricity or a collision, etc.

Other manufactures do the same for trunk install batteries. The 2nd gen Miata is another example...