In the trunk.
the battery is in the trunk under the trunk floor mat
Try the battery.
Yes, as long as you get the right battery so that it is an identical fit. Either get a BMW battery, or an Interstate MPT-H6. You will have to plug one of the vents on the interstate battery, and use the vent hose from your original BMW battery.
In the trunk, below the trunk floor. The trunk floor is a panel that lifts out to access the battery.
The 2013 BMW Z4 has 16 valves.
The 2006 BMW Z4 has 24 valves.
The 2007 BMW Z4 has 24 valves.
The 2012 BMW Z4 has 16 valves.
The 2008 BMW Z4 has 24 valves.
The 2011 BMW Z4 has 24 valves.
The 2010 BMW Z4 has 24 valves.