The problem is that you don't want to disconnect the battery for this test. You want to measure the current when you turn the key off, and then watch it over time, and see that it drops down as various modules go to sleep. Disconnecting the battery doesn't let you do this. Diyanich is saying to use the ammeter to keep the circuit connected. I would rather use an inductive (clamp-on) ammeter.

__________________
2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue