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Battery Connection Notes and Replacement
 
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Pelican Technical Article:

Battery Connection Notes and Replacement

Steve Vernon

Time:

30 minutes30 mins

Tab:

$0 to $200

Talent:

*

Tools:

13mm socket and extension, 10mm wrench

Applicable Models:

Mercedes-Benz W204 (2008-15)

Parts Required:

Battery

Hot Tip:

Store any aftermarket radio codes you may need

Performance Gain:

Car starts

Complementary Modification:

Change cabin air filter

The battery in the Mercedes W204 is located in the rear right hand side of the engine compartment by the A-pillar and window base and is covered by a plastic air box. When replacing your battery make sure to use a high quality unit; they tend to last longer than the cheaper ones. Replacing the battery is easy and can usually be done in less than 30 minutes. This is a great job to start your DIY journey. Working safely with your battery is an important aspect of fixing things yourself.

Before disconnecting your battery, remove the key from the vehicle and store it in a safe place and note any radio presets. When a battery is reconnected or loses its charge the following items may need attention, depending on vehicle equipment. You may have to reset your clock, enter radio presets, initialize power windows and initialize the sunroof.

The battery in the Mercedes W204 is located in the rear right hand side of the engine compartment by the A-pillar and window base and is covered by a plastic air box (red arrow).
Figure 1

The battery in the Mercedes W204 is located in the rear right hand side of the engine compartment by the A-pillar and window base and is covered by a plastic air box (red arrow).

There are three main areas regarding the battery, the battery and cover (red arrow), the power distribution box (yellow arrow) and the ground post for jump-starting (green arrow).
Figure 2

There are three main areas regarding the battery, the battery and cover (red arrow), the power distribution box (yellow arrow) and the ground post for jump-starting (green arrow).

If you need to jump-start your vehicle you do need to directly connect the jumper cable to the battery.
Figure 3

If you need to jump-start your vehicle you do need to directly connect the jumper cable to the battery. When jump-starting: Be sure to work in a well-ventilated area. Batteries can produce an explosive gas. Wear gloves and eye protection. If battery acid comes in contact with your skin, immediately flush the area with water and seek medical assistance. Move both vehicles close together but do not allow them to touch. Turn the ignition OFF in both vehicles. Connect one end of the positive jumper cable to the positive (+) battery terminal of the vehicle with the good battery. Slide back the protective cover and connect the other end of the positive jumper cable to the positive (+) junction terminal (yellow arrow). Connect one end of the negative (-) cable to the negative (-) battery terminal of the vehicle with the good battery. Connect the other end of the negative (-) jumper cable to the negative (-) junction post beside the coolant reservoir (red arrow). Start the engine on the vehicle with the good battery. Allow it to idle and then raise the engine to 2000 RPM. Next, start the engine of the vehicle with the discharged battery. Once the vehicle with the discharged battery starts, shut OFF any electrical accessories, radio, HVAC blower, etc. Carefully disconnect the jumper cable in the reverse order that you connected them. Allow the vehicle with the dead battery to idle to recharge the battery.

The main distribution of power is at the junction or distribution box.
Figure 4

The main distribution of power is at the junction or distribution box. To access this you need to remove the cover by pushing in the four plastic clips and lifting the cover off. The yellow arrow indicates the cover for the positive jump-start terminal.

With the cover off you can see how the power is split and distributed elsewhere in the vehicle (red arrow).
Figure 5

With the cover off you can see how the power is split and distributed elsewhere in the vehicle (red arrow). If you need to perform any work on the box or replace any of the distribution cables make sure to disconnect the battery first.

There are three clips that hold the air box cover on protecting the battery.
Figure 6

There are three clips that hold the air box cover on protecting the battery. Use your hands and unclip the clips and lift the box off.

With the cover off you can see the positive (yellow arrow) and negative (red arrow) posts on the battery.
Figure 7

With the cover off you can see the positive (yellow arrow) and negative (red arrow) posts on the battery. When working on a battery always disconnect the negative post first and place it out of the way somewhere where it cannot accidentally make contact with the post again. Use a 10mm wrench and disconnect the negative post and then the positive.

With both terminals disconnected (negative first) use a 13mm socket with a long extension and remove the two bolts holding the battery hold down in place (red arrows).
Figure 8

With both terminals disconnected (negative first) use a 13mm socket with a long extension and remove the two bolts holding the battery hold down in place (red arrows).

Remove the bolts and the hold down plate from the tray.
Figure 9

Remove the bolts and the hold down plate from the tray.

Carefully lift the battery straight up and out.
Figure 10

Carefully lift the battery straight up and out. It is very heavy so have a strong friend help if needed. Always clean and inspect the battery tray area. If there has been leaked battery acid or rust has started you need to take care of this right away, before you install a new battery. Installation is the reverse of removal.

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Comments and Suggestions:
Bimmerland Comments: You can use a small 12 volt supply without damaging a control module. The jumper /charging connector is wired directly to the positive battery cable so disconnecting the battery while having a small 12 volt power supply will not damage any modules. Just take care the the positive cable doesn't get grounded by accident.
April 26, 2017
  Followup from the Pelican Staff: less than 1 amp can damage a control module. A small 12 volt supply will have an amp or more. - Nick at Pelican Parts  
Bimmerland Comments: Why not put a temporary 12 volt source so the computer does lose anything. I small 2 amp charger should work.
April 24, 2017
  Followup from the Pelican Staff: You can accidentally short something and damage a control module. - Nick at Pelican Parts  
Mb Comments: Pepboys charges extra to install - claims they need to use scanner to reset steering angle sensor etc. I just took my battery out after connecting spare battery to power distribution terminal yellow arrow to maintain power ... seems to be fine so far ...

Btw - do you have part number for the cover on the power distribution box - mine is missing -2008 c300 sport - thx
April 11, 2017
  Followup from the Pelican Staff: I’m not the best with part numbers, I am the technical question person.

Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need. - Nick at Pelican Parts
 
JMorgan Comments: The gents at Autozone claim the stealership needs to replace the battery due to computer programming issues. Is this the case??? If its just re-initializing windows and sunroof and radio presets then its a no-brainer DIY! Thanks.
February 16, 2017
  Followup from the Pelican Staff: It is possible that the battery needs to be registered with the vehicle. This changes the charging strategy and is designed to help your new battery last longer. - Casey at Pelican Parts  
johnboy Comments: Mine is on the other side - real strange - looks the same but just swapped over
January 27, 2017
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 

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Page last updated: Tue 5/30/2017 03:15:15 AM