is there a key needed to get to the battery in 2008 buick enclave to change the battery

I would read your owners manual.

The enclave battery is located behind the passanger front seat. there is a panel that comes off, looks like maybe a 25 Torx, the factory floor mat covers the panel, you do not need a key.

The 2008 Buick Enclave batter is located inside the car, behind the passenger seat. Do the following: If you have enough power, move the passenger front seat all the way forward. Open the rear passenger door and look down at the floor and you should see a 10 torque screw on the floor. That is the battery compartment. Remove the screw and the panel. You should see the battery then. You will need a socket or a wrench to remove the cables and there is also a security block on the bottom that you will need an extension to reach to remove. Lastly, there is a tube that allows the battery to vent overboard which is important. Remember to remove it and reinstall the tube when you get your new battery. It is recommended that you always open the drivers side door prior to disconnection of the negative cable to prevent memory storage, but if the battery is dead, it shouldn't matter anyway. Good luck and hope this helps!