Where is the auxiliary battery located on a Mercedes ML350?

The auxiliary 12‑volt battery is typically located in the trunk on the right‑hand side behind the interior trim panel.

For some ML350 variants and model years, especially those with Start‑Stop systems, the location can vary: it may be under the rear seat or in the engine bay. Check your vehicle’s owner’s manual or VIN‑specific diagrams for the exact spot.

Location by model year and generation

Different ML350 generations and configurations place the secondary battery in slightly different areas. The following outlines common possibilities you may encounter.

• Trunk-mounted on the right side behind the interior trim panel in most modern ML350s (especially newer W166 variants and later).


• Under the rear seat or within the cargo area behind a side panel in some older ML350s or non‑Start‑Stop configurations.


• In a few cases, the auxiliary battery can be located in or near the engine bay, depending on market or build specifics.

In practice, the trunk right‑side location is the most common setup for recent ML350 models, but always verify for your exact year and configuration.

How to locate and access safely

The following steps help you identify and reach the auxiliary battery in an ML350 you own or service.

1. Park on a flat surface, turn off the ignition, engage the parking brake, and remove the key or ensure the car is fully powered down.


2. Open the trunk and inspect the right‑hand side inside the cargo area for a battery cover or a battery box behind the trim panel.


3. Carefully remove the interior trim panel or carpeting over the suspected battery area, noting fasteners so you can reinstall later.


4. Look for a 12V or “Aux” labeled battery on the case to confirm you have found the auxiliary battery, not the main engine‑bay battery.


5. If you cannot locate a battery in the trunk, check under the rear seat by lifting the seat base or removing the floor panel to reveal a secondary battery box.


6. If the battery is still not found, consult the owner’s manual or a Mercedes dealer for a VIN‑specific diagram showing the exact location.

When handling the auxiliary battery, observe safety practices: disconnect the negative terminal first, avoid shorting terminals with tools, and consider professional assistance if you are not familiar with automotive electrical work.

Safety and maintenance notes

The auxiliary battery powers ancillary electronics and, in many cars, supports Start‑Stop functionality. If you’re replacing or disconnecting it, ensure the vehicle is fully powered down and follow the manufacturer’s guidance to avoid electrical faults or warranty issues.

Summary

Across the Mercedes ML350 lineup, the auxiliary 12‑V battery is most commonly found in the trunk on the right side behind the interior trim, though some early or alternative configurations may place it under the rear seat or in the engine bay. Always check the owner’s manual or a VIN‑specific Mercedes diagram to confirm the exact location for your vehicle, as configurations can vary by year and market.

How much will it cost to replace my Mercedes-Benz auxiliary battery?

What happens when a Mercedes auxiliary battery dies?

Your Mercedes-Benz C 300's auxiliary battery is an integral part of your vehicle's operation. Without it, your instrument cluster, dashboard error messages, and other electrical components such as GPS will not turn on, impacting the overall driving experience.

Can I drive my Mercedes without an auxiliary battery?

A: Yes, you can usually still drive your car, but you shouldn't ignore it. A bad aux battery puts extra strain on your main battery and alternator, which can lead to more expensive repairs down the road. You will also lose features like Start-Stop functionality.

Where is the auxiliary battery located in ML350?

The auxiliary battery in a Mercedes ML350 is located in the boot next to the spare wheel. This secondary battery powers the entertainment system, windows, and lighting during engine start-up.