Cayenne S Spare Tire
 

I hope I'm not asking a common question, but nothing popped up in the archives when I searched.

I have an '04 Cayenne S that I bought aftermarket. When I went to change a flat, I found that what looked like a spare tire holder only contained what appears to be a second battery.

1) Do I need that battery?
2) What do I need to change to put a spare in there?

Thanks!

Craig