For the DIY car enthusiast, battery replacement on a Mercedes-Benz is a fairly easy task to master. All you need is a replacement battery and a few basic tools. Beyond that, you need to locate where the battery is in the vehicle and know how to disconnect it to make way for the new one. Moreover, you need to know when it is time to make a replacement and the type of battery most suited for the vehicle. Read on to learn how to replace a battery in a Mercedes-Benz.
Signs a Mercedes Battery Needs Replacement
The most common sign a Mercedes-Benz is due for a battery replacement is when the vehicle is difficult to start each day. If it takes several seconds just to get the motor to power on after you turn the key, the battery is probably running out of life. If the engine sputters for several seconds as you turn the key, or the engine fails to start until the second or third try, the battery is probably hanging by its last thread.
Alternately, you might see a warning on the dashboard that the charging system is malfunctioning.
Safety Precautions When Changing a Mercedes Car Battery
When you change out a battery on a Mercedes-Benz, you must be careful to avoid a terminal short. Therefore, it is crucial to prevent contact between the positive terminal and the negative terminal, and also between the positive terminal and the frame of the vehicle. Basically, the positive terminal of the battery must not make contact with any metal parts of the vehicle.
Tools Needed for Changing a Mercedes Battery
To change out a battery on a Mercedes-Benz, you will need to have the following tools on hand:
- 10mm socket wrench — You will need this to disconnect the battery from the positive and negative terminals.
- 13mm socket wrench — You will use this when you take out the bracket that holds the battery in place.
- 8″ extension — You may need one of these to loosen the battery from the terminals.
- Battery post cleaner — Once you've taken out the old battery, you might need to clean the battery post.
Aside from these tools, you will just need the right kind of replacement battery for your Mercedes.
How To Change a Mercedes Car Battery
Park the Vehicle in a Secure Spot.
Before you even begin, make sure to park your Mercedes-Benz on a stretch of concrete with the emergency brakes fully extended. This way, you can be sure the car will not roll when you're in the middle of your work. If the car moves as you're changing its battery, neighboring components could wind up damaged in the process.
Find the Battery.
In most Mercedes-Benz models, the battery is on the right on the inside of the trunk. In rarer models, you'll find the battery beneath the back seat. In the Mercedes-Benz W203 and R170 models, for example, the battery is on the passenger side of the engine sink. Other Mercedes models with unique battery locations include the following:
- W210 — The battery is beneath the rear seat.
- W461/463 — The battery is beneath a cover in the floorboard, behind the center console.
- W164/166/151 — You'll find the battery below the front passenger seat.
If the vehicle contains two batteries, check the trunk for the system battery and under the hood for the starter battery.
If the battery is under the hood of the Mercedes, you will need to use the 10mm socket to undo the battery cables and top mounts. To disconnect the bottom mounts, you will need to use the 13mm socket.
The first step is to remove the old battery. To begin, unplug the negative battery terminal. Loosen the 10mm bolt that holds the battery in place. If you still have difficulty pulling the terminal, twist it first. Be careful not to force anything. If the clamp of the battery remains stuck in place, try using a special terminal puller.
Unplug the positive battery terminal. You will need to insulate this part with electrical tape, as it is crucial not to let the positive terminal make contact with any metal part of the Mercedes, including the car frame.
Take out the bracket that keeps the battery in place. The bracket is fastened with a 13mm bolt and typically requires the use of an extension to remove. With the bracket out of the way, remove the dead battery from the car. Beware of the weight factor, as car batteries are usually heavy.
On some models, you might need to take off a cabin air filter to access the battery. Three snaps hold the air filter box in place, which you can pop out with a screwdriver.
If the battery is in the trunk, it might be wrapped with a buckled strap. Undo the buckle and pull the strap aside. The battery itself should be on the right side of the trunk under the floor panel. On S-Class and AMG S-class Mercedes vehicles, the bottom panel of the trunk is fastened with a pair of T20 Torx bolts. Once you have removed these bolts, you can slide this panel to access the system battery.
On Mercedes vehicles that have both a system and starter battery, the latter connects first. As such, you must disconnect the negative cable of the starter battery, located under the hood, before you change out the system battery. Once you have installed the new system battery, reconnect the starter battery. The Mercedes vehicles with two batteries are the S-class (221) and SL class (230/231) models.
Install a New Battery.
With the old battery out of the way, it is now time to install a new battery in your Mercedes-Benz. The steps involved with battery installation are the complete reverse of the steps you followed to remove the older battery.
Take the new battery and place it in the battery tray. Next, put the battery bracket back into place. Reconnect both the positive and negative battery terminals, respectively.
Once you have installed the new battery in the vehicle, it is time to run some synchronization procedures to ensure your Mercedes is good to go.
- Synchronize the Windows.First, you will need to synchronize the automatic functions that open and close the windows with the new battery. To get them synchronized, press the window switch and hold it down until the window is completely closed. Once the window is closed, keep holding the button down for another three seconds. Then, press the window button in reverse to open it. Once it has fully lowered, continue pressing the button for an additional three seconds. Repeat these steps for each window.
- Synchronize the Sunroof. As with the windows, the sunroof will not be synchronized at first to the new battery in your Mercedes-Benz. To synchronize, press the button to open the sunroof. Once the sunroof has fully opened, hold the button for an additional three seconds. Then, reverse the switch to close the sunroof. Once the sunroof has fully closed, keep pressing the button for three more seconds.
- Calibrate the Steering Wheel. With the new battery installed and the windows and sunroof synchronized, put the key into the ignition and power on your Mercedes-Benz. The moment the vehicle starts, you should see some warning messages on your dashboard monitor. Namely, the ESP message should come on with a warning light.To reset the ESP, turn the steering wheel as far as it will go to the left and hold it for two seconds. Then turn the wheel as far as it will go to the right and hold it for two seconds. Repeat those steps — all the way to the left for two seconds and all the way to the right for two seconds. Cut the motor, then restart the car. The vehicle should now power up as usual, with no ESP warning lights.
- Optional: Use Jump Starter to Avoid Synchronization.If you do not wish to go through the steps of window synchronization, sunroof synchronization and wheel configuration, there is an alternative. You keep the Mercedes-Benz connected to a power source as you change out the battery. You can do this with jumper starters. Only attempt this if you have experience with jumper starters, as this will require some tricky steps.As you change the battery, the jumper cables — or, alternately, a backup battery — will need to have a connection to the jumper terminals under the hood of the Mercedes-Benz. It does not matter where the battery is in a given model, as the terminals are always under the hood.
Slide the red cover off the jumper terminal to view the positive and negative posts. You will need to connect the jumper starter to the positive battery terminal. Alternately, you can use a 12-volt backup battery to provide a power source as you change out the battery.
Set the Time.
Resort to the owner's manual of your Mercedes-Benz to reset the clock after installing your new battery. Instructions for the time-setter vary between different models.
Enter Radio Code.
On certain Mercedes models, you need to enter a radio code to get the radio synchronized with the battery. To find out whether this applies to your vehicle, consult the owner's manual, which should list the code you will need to enter for the radio. If the manual doesn't provide this information, call the dealer from whom you purchased the vehicle. They should be able to access the radio code when you tell them the VIN.
Mercedes-Benz Replacement Battery Cost
The price for a new battery on a Mercedes-Benz will generally range from $280 to $400. However, you can cut the cost of battery replacement by as much as $100 and sometimes even $200 if you opt to do the replacement work yourself. You can generally save by choosing aftermarket batteries over OEM ones.
Select a Replacement Battery for Your Mercedes-Benz
Any battery that goes into your Mercedes-Benz must match the group size of the old battery. The majority of models from the automaker are equipped with an AGM H8 battery. As you shop around for a replacement battery, it should probably be a Group 49 AGM battery.
The best batteries for a Mercedes-Benz are generally the absorbed glass mat (AGM), which offer high accessory load for vehicles in this class. The battery should also have the same cranking amp and reserve capacity as the old battery.
The basic specs on a Mercedes battery are as follows:
- Group size: H8 / group size 49 / 94
- Battery type: AGM
- Cold cranking amps: 850
Most Mercedes cars come with a BCI Group 49 battery.
- Exide Edge 94R AGM battery
- ACDelco AGM 94 battery
If you are concerned about replacing the battery in your vehicle with an exact match, consult the user's manual or contact the dealership that sold you the vehicle to identify the battery type.
Mercedes Battery Warranty
Depending on the dealer, you might be able to get a longer warranty with an aftermarket battery than you would from Mercedes-Benz dealerships, which typically offer two-year warranties. While some aftermarket sellers will only offer a one-year warranty, others offer three-year warranties, which makes it wise to shop around.
How Long Does It Take to Replace a Battery in a Mercedes-Benz?
The steps required to replace a battery on a Mercedes-Benz are straightforward, and you can complete them in less than a half an hour. When you compare this to certain other vehicles, you are indeed lucky to own a Mercedes. On a BMW, for example, the steps required for battery replacement are far more complicated, as you have to clear the power module of the charging history of the old battery — a step that requires a scan tool.
On a Mercedes, by contrast, all you need to do is remove the old battery, install the new one and calibrate the windows, sunroof and steering wheel. You won't need special tools to change the battery in a Mercedes-Benz.
Get a New Battery Installed on Your Mercedes-Benz
Whenever you replace a battery or any other part of a Mercedes-Benz, it is important to find a trustworthy specialty dealer that offers parts and services at reasonable prices. At Burdi Motorworks, we have offered vehicle repairs and parts for Mercedes owners in and around Chicago, Ill., for more than 40 years.
Located in Schiller Park by the O'Hare Airport, our facility is family-owned and -operated. It is our mission to offer the best-quality repairs and services on Mercedes-Benz vehicles. When you need a new battery or any other repair work or service on your Mercedes, contact the specialists here at Burdi Motorworks.