
The steps to replace the key battery for the new Mercedes-Benz S400 are: 1. Push the marked switch upwards to remove the mechanical key; 2. Open the key casing, then pry out the old battery and replace it with a new one. The dimensions of the new Mercedes-Benz S400 are: length 5290mm, width 1921mm, height 1503mm, with a wheelbase of 3216mm, a fuel tank capacity of 76 liters, and a trunk capacity of 556 liters. The new Mercedes-Benz S400 is equipped with a 3.0T twin-turbocharged engine, delivering a maximum power of 230kW and a maximum torque of 450Nm, paired with a 9-speed automatic manual transmission.

Last time my Mercedes S key fob ran out of battery, it was quite simple to replace it myself. First, confirm the key model is the smart version - the small groove on the back is the prying point. Use a small flathead screwdriver or thin tool to gently pry open the casing along the groove, being careful not to scratch the plastic. After removing the cover, you'll see the coin battery holder - typically CR2025 or CR2032 models. Use plastic tweezers to remove the old battery, noting the positive/negative orientation. Press the new battery in firmly until it clicks, then align and snap the casing back together. It's safest to wear anti-static gloves throughout the process. Batteries bought from roadside watch repair shops for about 5 yuan can last two years, but avoid cheap no-name brands. The whole DIY replacement takes about 10 minutes, compared to over 300 yuan at the dealership.

Replacing the key battery requires careful attention. I've disassembled several Mercedes key fobs, and the new S400's smart key has a one-piece snap-on casing. Locate the hidden seam near the keyring, and you can slowly pry it open with your fingernail. Be careful not to let sweat touch the internal circuit board or let metal contact the terminals. The battery is usually a Panasonic or Sanyo CR2025 model - genuine ones from the supermarket will work. After replacement, test the unlock button sensitivity by pointing it at the door handle when pressing. If the car shows a key malfunction warning, don't panic - try removing and reinserting the battery a few times. One last tip: keep the smart key away from electronic devices like phones before replacing the battery to avoid interference.

Key Points for Replacing the Battery in a Mercedes Smart Key: 1. Pry open the shell at the notch marked on the back of the key; 2. Identify the correct battery model (CR2025/CR2032); 3. Remove the old battery with insulated tweezers (to prevent static electricity); 4. Place the new battery with the positive side facing up; 5. Press the shell until you hear a click to ensure proper closure. The entire process takes less than three minutes. Just prepare a 3V coin battery and a small pry tool in advance. The price quoted by a 4S shop is enough to buy thirty batteries. After replacement, test the remote start and comfort access functions to ensure they work properly.


