where is the battery located in a clk 500 mercades benz

Your batery should be located in your trunk, you can release the emegency key from your key fob and use it to gain entry to your trunk. the manual key lock is located above the liscence plate next to the handle.

they are difficult at times, and you may have to finagle it, to the left., (the key) to release the trunk, unless you get a jump on the terminals under the hood, then push the button, once access to the trunk is gained, to the right, fender, there will be a "pull down lever/arrow" pending year, usually arrow is white, the rear interior fender cover will pivot, and down at about tire level, is a giant battery....IMPORTANT is the small hose "breather" for the new one...personal preference in European cars is spend the extra and go with Interstate....probably looking around $200. pending store.