How to Replace the Battery in an Older Mercedes-Benz S300 Key?
2 Answers
Method for replacing the battery in an older Mercedes-Benz S300 key: 1. Flip open the tab at the rear end of the key to remove the mechanical key; 2. Insert the mechanical key into the side slot of the key groove, press the internal gray button, and with the other hand push the rear end of the key upward. When a gap opens, remove the mechanical key; 3. Use your hand to take out the rear end to replace the battery. After installing the new battery, reinsert the key bracket. The Mercedes-Benz S300 has a length of 5230 mm, width of 1871 mm, height of 1485 mm, a wheelbase of 3165 mm, a fuel tank capacity of 101 liters, a trunk capacity of 560 liters, a minimum ground clearance of 190 mm, and a body weight of 2020 kg.
Last time I replaced the battery for my Mercedes S300 key, I remembered it was the old folding type, which was quite simple to open. Just buy a CR2032 button battery, available at supermarkets, and don’t go for cheap options—choose branded ones like Panasonic for better durability. There’s a seam along the edge of the key; gently pry open the casing with a small plastic pry tool or screwdriver, avoiding excessive force to prevent scratching the plastic. Once opened, you’ll see the battery inside. Remove the old one, insert the new one with the positive side facing up (don’t reverse it), then align the casing and press it back until it clicks securely. Test the lock and unlock functions immediately after to ensure everything works. It’s wise to keep a spare key and battery in your car, as key batteries typically last 2-3 years—delaying replacement might lead to accidental locking, which can be troublesome. Remember to work with dry hands to prevent static and avoid humid environments to prevent contact point corrosion.
