How to Replace the Battery in an Older Mercedes-Benz S300 Key?

[BarrettLynn]

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.

[MacKarter]

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.

[DiLandon]

As a car owner, I pay close attention to key maintenance. The Mercedes-Benz S300 key typically has a slim design, and changing the battery requires observing its structure first. There may be small screws at the bottom of the key casing—remove them with a micro screwdriver. If there are no screws, simply pry open the seam. Remove the old CR2032 battery carefully, avoiding contact with the metal terminals, as static electricity can damage the internal circuitry. Place the new battery in the correct position, ensuring it fits snugly against the terminals to prevent looseness. When reassembling the casing, press evenly to avoid leaving gaps that could let dust in. Test the key by pressing the buttons multiple times to confirm that both starting and locking functions work properly. The DIY process isn’t difficult, but use plastic-tipped tools to avoid scratching the key, and choose the correct battery model to extend its lifespan. After replacement, it’s advisable to note the date for future reference—regular checks can prevent sudden malfunctions.

[OChase]

Replacing the battery for a Mercedes S300 key is actually quite simple. I usually just buy a CR2032 battery and a small tool. There's a notch on the edge of the key where you can gently pry it open with your finger or a small blade. Replace the old battery with a new one, then snap the cover back on and press firmly. After completing the process, just test the buttons—no complicated steps needed. The battery typically lasts about two years, so it's good to keep a spare in your bag for emergencies. That way, you can quickly handle it when the key runs out of power. It's advisable to make this a routine habit rather than waiting until there's a problem. Just be careful not to drop it during the process.