Keys via Jessica Merz on Flickr | CC 2.0

How to Replace A Mercedes Key Battery

Mercedes keys or key fobs that aren’t working dependably likely need battery replacement. You can take a few steps to get your key to work like it’s new again. The specialty batteries in key fobs can last five to 10 years, but the life span varies depending on the frequency of use, temperature extremes, and battery quality.

Find out how to spot a worn-out battery, which type of battery to buy, and how to install it yourself. Mercedes-Benz of Fairfield is available to answer any questions you may have to help you with this or any other maintenance for your Mercedes-Benz. Just give us a call at (707) 430-0101.

How Do I Know When the Battery Needs Replacement?

Watch for warning signs that your key fob battery is starting to wear out, so you don’t get stranded in the Fairfield area or while traveling a longer distance. Watch for one or more of the following warning signs that can develop over time:

• Starting your car becomes more difficult or takes multiple attempts.
• Locking and unlocking doors or setting off the panic alarm becomes difficult or isn’t possible.
• A dashboard warning sign indicates a charging system problem.

Buy a Quality Battery

Since your key fob is essential to your Mercedes-Benz, purchase a top-quality battery. Not all batteries are equal, and you get what you pay for in most instances. Highly rated CR2025 batteries include Energizer Lithium with a 10-year shelf life and operating range of -22 to 140 degrees Fahrenheit. Duracell Procell Lithium batteries are also highly rated and can last up to 10 years in storage. Other quality batteries are available from a variety of manufacturers. Check consumer ratings, life span, and ability to function through temperature extremes.

What Are the Steps to Battery Replacement?

Once you’ve determined the key fob battery needs replacement, follow four basic steps to get it back to peak performance:

Determine Whether You Have a SmartKey or a Chrome Key

• SmartKey fobs are in older Mercedes models and are encased in plastic.
• Chrome Key fobs are encased in metal and have two types.
• Older models have a circular panic button, while newer models have a triangular panic button.

Buy Replacement Batteries

• SmartKey fobs and older Chrome Key fobs take two CR2025 batteries.
• Chrome Key fobs for newer models require one CR2025 battery.

SmartKey Fobs Have Special Battery Replacement Steps

• Find and pull the sliding tab at the end of the key holder.
• Pull the valet or mechanical key and move it to the open slot in the corner, where it will pop the battery cover.
• Remove the cover for the battery compartment.
• Remove and replace both batteries, ensuring they both face the correct way.

Reassemble by Inserting the Narrow End of the Cover First, and Check to Make Sure It Works as Expected

• Chrome Key fobs for newer models have their own instructions.
• Pull the tab at the bottom of the key fob, removing the valet key.
• Push the key into the narrower end of the slot, which will help remove the battery cover.
• Remove and replace the battery or batteries, ensuring correct placement.
• Reassemble, inserting the narrow end of the cover first, snapping it into place, and checking to make sure it works as expected.

Tips: Make sure any protective stickers are removed from the battery so it will make contact with the key fob. A small screwdriver may help remove the old batteries but be careful not to force them out.

If you’re unable to follow these steps to replace the key fob battery, schedule an appointment with the experts at Mercedes-Benz of Fairfield.

What Happens If the Battery Quits Before I Can Replace It?

Unexpected key fob failure may happen due to a bad battery or damage to the key fob unit. Fortunately, the metal key within the fob can work if you are in a pinch. The following instructions work for models that have a Start/Stop button:

1. Remove the metal key from the key fob by sliding a locking tab over to the side.
2. Unlock the door with the key, noting this will likely activate the alarm until the key is in the ignition.
3. Remove the Start/Stop button from the ignition lock by gently pulling it. Insert the metal key, making sure to have your foot on the brake and the transmission in park.
4. Turn the key to start the engine, letting go of the key once it starts up. Keep the Start/Stop button in a safe place until you have a chance to replace the battery or have the key fob repaired. Your dashboard may have a missing key or key battery-low warning.

If your key fob quits while driving, you will be able to keep driving since the fob is designed for unlocking and starting only. The problem will occur when you shut off your car and attempt to restart or lock it.

Remote Options for Accessing Your Mercedes-Benz

If your key fob quits working or is misplaced, you may have remote options to get back on the road. Some newer models will have the Mercedes Me Connect option, where you can use your smartphone to unlock, lock, or remotely start your engine.

In addition to helping in a pinch, Mercedes Me Connect makes life easier, from planning a trip to monitoring your vehicle. Remote engine starting allows you to heat or cool the cabin before hitting the road. It offers an easy location of your car if it’s near or far away and reviews data like mileage, fuel level, tire pressure, fluids, and other vital information. You can even communicate with your car’s navigation system.

Do You Need Assistance or Other Services?

If you’re having difficulty getting your key fob to work or have any other questions, look into Express Service at Mercedes-Benz of Fairfield. A team member will be happy to help you with your key fob as well as many other services.  We can help you with synthetic oil changes, multi-point inspections, paintless dent removal, filter replacement, brake and tire service, fluid checks, lamp checks, and other assistance to keep your Mercedes-Benz in top shape.

You can find us at 2950 Auto Mall Parkway in Fairfield, CA, or call our service department at (707) 430-0102. You can also complete our secure online form to get started today.