My buddy asked me to replace both batteries in his 2004 SLK 350. He's overseas, the car has its original batteries, he knows they're dead, and he'd rather not spend a day fiddling with this when he comes home for a short while, so he asked me to do this favor.

The problem is I don't know where the batteries are located on the car, and I'd like to buy the batteries in advance to prevent iterative trips. His car is 40 miles away. Can someone tell me where the batteries are located? And which batteries do I buy?... Group 48 or Group 49?

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95 E320 Cabriolet, 159K