Mercedes Benz Battery Replacement Instructions – DIY Guide

Have you been having trouble lately in trying to start your Mercedes Benz? Well, you do know your vehicle is in good shape as you never miss a maintenance date with your service center. What then could the problem be?

Well, often the culprit of hard starts and failing electronic in vehicles is the battery. Even though you’ve meticulously serviced your vehicle for quite some time, wear and tear, or complete breakdown of certain components is inevitable, and will therefore need replacing. The battery is one such component, and a very important one at what it does.

So, what are the Mercedes Benz battery replacement instructions? Well, like any manufacturer out there, Mercedes have their own special way of doing things. In a Mercedes Benz, there is a procedure to how the battery is replaced. This procedure is essential as the vehicles’ layout is not typical, and some functionalities depend on the presence of a battery.

Typically, a car battery will last anywhere from five to six years before needing replacement. However, they will fail and you’ll need to replace it. Before you embark on replacing the battery, you’ll need a few tools with you:

• A 3/8-inch (10 millimeter) socket wrench to loosen the battery terminals from the battery.
• Another 15/32 (12 millimeter) socket wrench that you will have to use when separating the battery from the bracket holding it.
• An 8-inch extension you will use to remove the battery terminals from the battery.
• Battery post cleaner or a bottle of coke that you will use to clean the battery terminals in case there was corrosion.
• A tub of petroleum jelly that you will apply on the new battery’s posts to help reduce corrosion.

How to Change a Mercedes-Benz Battery: 4 Steps


The following are the steps necessary to remove and replace the car’s battery.

1. Park the Vehicle

Well, this is a bit obvious, isn’t it? You’ll need to do so at a secure location such as your driveway or that of a service center. Ensure that where your parked is fairly flat that your car won’t roll away, or better still, engage the parking brakes for extra safety.
You don’t want your car to roll away from you while you’re working, and possibly into moving traffic.

2. Getting to the Battery

As mentioned earlier, each manufacturer has their own little quirks that translate in how they manufacture their vehicles. Mercedes are not immune to this. While other manufacturers can do different things such as using rotary engines, boxer engines or mid-mounted engines, Mercedes decided to remove the battery from the engine bay.

The placement of the battery is different in some models. However, a good number of the vehicles have their batteries inside the trunk, on the right side. For other models, the placements may vary. These can be:

• Mercedes Benz E-Class (W210) where the battery is located under the rear seat.
• Mercedes Benz G-Class (461 and 463) where the battery is located inside the cabin, under the cover of a floorboard, right behind the center console.
• Mercedes Benz M-Class (W164, 166) and the Mercedes Benz SL-500 (W151) where the battery is located underneath the front passenger seat.

There are some models with two batteries because of the greater electrical demand in these models. These include the S-Class (221), the SL-Class (230/231), the E-350 (W211), the E500 among many others. These batteries will usually be located one in the trunk, and the other in the hood right next to the wiper system. The one in the trunk is used to power the systems while the one under the hood is used to power the car’s starter.

3. Out With the Old, in With the New

You’ve now done some little digging around and you know where your battery is located. It’s now time to grab your tools and get down to work. Grab the 3/8-inch socket wrench and get to work loosening the battery terminals and the mounts at the top. For the bottom mounts, use the 15/32-inch socket wrench to get them loose.

You’re now free to unplug the battery from the car. You should start by unplugging the negative terminal first. This terminal is usually connected with a cable with black insulation. Also, the terminal connector is usually smaller in comparison to the positive terminal.

To loosen the terminal bolt, use the 3/8-inch bolt to get this done. In some cases, you might find that the terminal refuses to come off the post. Do not force it loose or try some percussive maintenance techniques as these may cause damages, or even battery leakages which can be hazardous. Try twisting the terminal until it wriggles free. If not, get yourself a terminal puller.

The next obvious thing to do is to disconnect the positive terminal. This terminal requires a bit of care as current flows out from it. If it touches any part that could cause serious damage to the electrical systems of the vehicle. This is because modern vehicles are grounded using the negative terminal.

If a positive terminal touches the frame, the voltage difference will cause significant amperage to flow from the battery and through to the frame. The result is melting of wires, melting of metal parts and even damage to the battery itself. It is for this reason that an insulator is placed on the positive terminal before the battery is moved from the holding bracket.

You could use a terminal cover as an insulator or in case there are none, a healthy wrapping of tape around the positive post will do just fine.

You can then use the 15/32-inch socket wrench to loosen the bolts and get the battery free from the bracket. In most cases, an extension will have to be used to add more torque while lessening effort. Now it’s just a matter of taking the battery out. Watch out for the weight though. Batteries are pretty heavy and you should brace yourself.

Installing a new battery is easy. It’s just a matter of reversing the order used in taking out the battery.

Since you took out the battery, the electronics powered by it would lose memory, and therefore some functions will be lost. Once the new battery is installed, it’s time to recover these functions.

4. Recover Lost Functions

As explained above, the removal of the battery will result in loss of functions. This is normal with all forms of computers. The memories of their computer and electrical systems are still powered by the battery, even when the machine or appliance is off. Take away the power source, and the memory is wiped clean.

You have a few tasks to complete in this step:

• Auto open and auto close windows: Once power is drained from the system, it will not remember even the simplest of functions such as one touch auto closing of the windows. To regain this function, you will need to pull up the window switch until it is all the way up. You will need to hold this position for three seconds.

Once this is up, hold it all the way down until it is fully open, and then hold the button down for another three seconds. For all windows to have auto functionality, you will need to do this procedure on all four windows.

• Auto open and auto close the sunroof: If you’re vehicle has a sunroof; you will have to follow the same procedure as that of opening and closing the windows. Hold the button to open and the hold for three seconds. Do the same for when the sunroof is in its closed position.

• Calibration of the steering wheel: As mentioned all functionality is lost with the loss of a power source. When you crank over the engine, you will notice on the dashboard the ESP light will come on. The ESP is Electronic Stability Program and is a way in which the vehicle’s computer works to keep you safe by monitoring how you control the vehicle.

To sort out this light, turn the power steering all the way to the left and hold for three seconds. Once done, turn all the way to the right and also hold for three seconds. Repeat this procedure twice more. Turn off the engine and then crank it over again. The ESP warning light should be sorted now.

• Setting the time: You will need to reset your vehicle’s clock. Every model has specific ways in this which is accomplished. For this, you will need to check with the manual that is specific to your vehicle model.

All these steps can seem a bit of a chore that you’d rather not have to deal with. Well, there is a way out of it, but word of caution: you need to be absolutely conversant with how jumpstarting work, or else you may end up completely shorting out the electrical system of your vehicle.

Mercedes models do come with a pair of jumper connectors under the hood, regardless of where the battery is located. You could connect another battery or a power source to these jumper leads. These will keep your car’s electrical system powered, thus maintaining their pre-programmed functions.