Battery acid is highly corrosive:
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2005 BMW 745i, 2005 BMW 745Li, 2004 BMW 745i, 2004 BMW 745Li, and 2003 BMW 745i. However, it is still accessible from the selected car via links, so may be relevant.
Do not allow any battery acid to come into contact with the eyes, the skin or clothing. Therefore wear protective clothing, gloves and goggles.
Do not tilt the battery, acid may emerge from the vent opening.