How to Replace the Battery in a Mercedes-Benz M-Class Key?
2 Answers
Mercedes-Benz M-Class key battery replacement steps are as follows: 1. Flip open the tab at the rear end of the key to remove the mechanical key: Insert the mechanical key into the side slot of the key, press the internal gray button, and with the other hand push the rear end of the key upwards. When a gap appears, the mechanical key can be removed. 2. Then use your hand to take out the rear end: You can now replace the battery. 3. After installing the new battery: Reinsert the key holder, and the key battery replacement is complete. The lifespan of a Mercedes-Benz key battery is generally two years, while the original factory battery can last up to six years. When the key battery is low, the Mercedes-Benz vehicle will provide two types of alerts. The first is when you press the ignition switch, the dashboard will display a message to replace the key battery. The second is when you press the lock or unlock button on the key, the indicator light on the key will dim or not light up.
I've driven a Mercedes M-Class for years and changed the key battery several times. First, locate the seam on the back of the key; use a coin or thin card to gently pry open the cover—avoid forcing it to prevent scratches. Inside is a CR2025 lithium battery. When removing the old battery, note its orientation: the positive side usually faces up. Before inserting the new battery, clean the contacts to ensure no dust is present. Snap the cover back on and press the unlock button a few times to test it. If there's no response, the battery might not be seated properly or the key may need reprogramming. I recommend buying branded batteries like Panasonic for longer life. Avoid exposing the key to high temperatures—typically, replacing the battery every year and a half is sufficient. Handling this small task yourself saves hassle and money.
