Test the battery with a tester.
Any auto parts that sells batteries can provide you with a replacement battery. If you want a OEM battery you will have to purchase it at a BMW dealer.
The battery for the 06 BMW 530xi is located in trunk, on the right passenger side. You will need to lift the spare tire lid in order to remove the right side molding cover. The battery is 850 CCA (Sears has a replacement for approx $140). Same model at BMW = $350.
You will need to go to a BMW Dealership in order to get a replacement key. Unfortunatlly, you will also need to bring a heavy wallet.
The original BMW style battery is the best option for you vehicle, I believe it is a 720 CCA rated battery, if not Douglas is the company that was making batteries for BMW at that time so you can try to locate a Douglas dealer.
Somewhere in my search for a battery, I saw a reference to Interstate Battery- MTP-91. Lo and behold it was the right size!
It is important to know where to get the replacement parts to a car. For a 1996 BMW a person can find the sunroof replacement parts at local auto part stores.
BMW's have auto-locks a little different from other cars, if your battery is dead, the doors won't open. To change the battery, you need to open the trunk, this is where the battery is located. You will see a panel with some screws, you need to remove that and underneath is the battery.
the battery is in the trunk under the trunk floor mat
No.
Where is the battery terminal on my BMW 528xi
Do you mean where is the battery in BMW 2006? Some BMW cars have battery in the Boot (trunk) and you have to lift the cover to see it
How do you charge a 2002 BMW Z3 battery