General notes on disconnecting battery:

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 disconnect battery leads and leads from alternator and starter motor while engine is running.
Cars with IBS on battery negative terminal:
Do not under any circumstances pull/lever off pole shoes by force.

Do not under any circumstances release socket-head cap screw of IBS.
Detach terminal of battery negative lead from car battery and second battery if fitted. Refer to 61 20 900 DISCONNECTING AND CONNECTING BATTERY NEGATIVE LEAD . Cover battery negative terminal(s) and secure.
When work is carried out on the electrical system, faults may be caused in the fault memories of some control units when the battery is connected.
When fitting terminal for battery negative lead: Tightening torque 61 21 1AZ. Refer to BODY EQUIPMENT - TIGHTENING TORQUES .