Can You Drive Mercedes without Auxiliary Battery?

Mercedes-Benz is popular for its high-tech engineering and advanced technology. For instance, Mercedes models come with two batteries; the main battery and the auxiliary battery. But can you drive Mercedes without an auxiliary battery?

Yes and no. Yes, you can drive a Mercedes-Benz without an auxiliary battery as it has two batteries. The first battery helps to run the car, while the second battery powers accessories. However, it’s not good to drive a car without an auxiliary battery as you don’t know how it will react.

If you start your car without an auxiliary battery or if the battery is faulty, you will see a flashing onboard computer error fault message, saying “auxiliary battery malfunction” or “stop vehicle shift to P leave engine running” warning message. The error code will only go away when you install an auxiliary battery or replace the malfunctioned one.

Where is the auxiliary battery located in a Mercedes?

Depending on your Mercedes make and model, you will find that the auxiliary battery is located in different places. Nevertheless, the major areas include below passenger seat, trunk, engine bay next to the passenger side, and behind the driver’s seat.

In the E-Class W211, the auxiliary battery is based in the engine bay on the passenger side. In the SK and SL models, the auxiliary battery is located behind the driver’s seat, while in the ML, R, and GL models, the battery is located under the passenger seat.

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What is the purpose of an auxiliary battery?

An auxiliary battery performs multiple tasks. In some vehicle systems, it can be utilized as a safety backup to support the main battery when needed to. However, most auxiliary batteries deliver voltage for particular accessories all the time.

The auxiliary battery on the Mercedes-Benz models is used to run some electronics. So, if the auxiliary battery is missing from your car, you can still drive it but some accessories won’t work. Besides, the function of the auxiliary battery varies from one Mercedes model to another.

In some models, the auxiliary battery is meant to operate the gear shift selector when the car dies. While in other models, this battery can run additional accessories, such as heated seats, sensors, stop/start functions, radio, COMAND, different radars, and much more. 

Which Mercedes models feature an auxiliary battery?

There are several Mercedes-Benz models that not only come with the auxiliary battery, but they are also usually affected by the auxiliary battery malfunction. Some of these models include:

  • Mercedes-Benz A-Class (W176, W177, CLA W117, CLS W218, C257)
  • Mercedes-Benz B-Class (W246, W247)
  • Mercedes-Benz C-Class (W204, W205, S204, S205, C205)
  • Mercedes-Benz E-Class (W211, S211, W212, A207, S212, GL X166, C207, ML W166, W213, C238, S213)
  • Mercedes-Benz Sprinters (W906 Vito, W639, W447)
  • Mercedes-Benz GLC-Class (X253, C253)
  • Mercedes-Benz G-Class (W463, G500, G55, G63 AMG)

Note that all of these Mercedes models feature a mini auxiliary battery that is located below the hood spare tire compartment, or dashboard, depending on the car model. So, check these areas first before you can confirm whether you have an auxiliary battery or a secondary battery.

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Can I drive my car with a failed auxiliary battery?

Of course, you can drive your Mercedes even with a failed or malfunctioned auxiliary battery. This is because Mercedes has two batteries and the battery used to run the vehicle is the main one. So, even though you won’t be able to utilize functions such as start/stop, you can still drive your car.

Is it possible to recharge an auxiliary battery?

Yes, it’s possible. The Mercedes-Benz auxiliary battery is a 12V 1.2 Ah battery. Therefore, the alternator charges this battery when the engine is running. Nonetheless, if the auxiliary battery voltage drops excessively, the alternator will stop charging it, and you will see an auxiliary battery warning sign on the dashboard.

Even with the warning sign coming on, you can still charge the battery if it’s still good. The only challenge is that you will have to remove the battery and charge it using a smart charger and re-install it when it’s full.

Besides, if the auxiliary battery is good but can’t charge, it may be a sign that the main battery is not full yet. To charge the auxiliary battery, the main battery has to be fully charged before power is delivered to the auxiliary battery. Thus, if the main battery has a lower voltage than usual, the auxiliary battery will not charge.

How long does the Mercedes auxiliary battery last?

An auxiliary battery can last long if properly maintained. If you take good care of this battery, expect it to be somewhere from 18 months up to 3 years of life from an auxiliary 12-volt battery. It can even last longer depending on how frequently you use it.

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What is the difference between a secondary and auxiliary battery?

People usually confuse these batteries to be one thing. Nonetheless, these are two different types of batteries. Normally, a secondary battery is utilized to power multiple electronic items, while an auxiliary battery is typically used as a backup to run the electronic shifter if the main battery dies. 

So, before you assume that your Mercedes-Benz has an auxiliary battery, check and confirm if it has a secondary or auxiliary battery. These usually vary from one Mercedes model to another. Besides, you don’t want to install the wrong battery on your car.

How much is an auxiliary battery?

The average cost of a Mercedes auxiliary battery is between $200 and $300. And if the battery is being changed at a Mercedes dealer, the labor cost will vary between $50 and $100. But if you want to save some cash, you can buy a new auxiliary battery and replace it yourself.

Bottom line

So, if you’re still wondering if you can drive a Mercedes-Benz without an auxiliary battery – yes you can. However, it’s not recommended as it’s not safe. The main reason why you should avoid driving a Benz without an auxiliary battery is that you don’t know how it will react.

Besides, some features that are powered by an auxiliary battery may be helpful in the smooth running of your car; thus, the unavailability of these features may cause trouble or an uncomfortable ride.

Edwin Odipo

Why do you love writing about cars? Cars make our lives easy. You can visit your distant friend, relative or even rush to the grocery store a few miles from your home with a lot of ease. Imagine how life was before the invention of cars?? To me, cars are a blessing that made life more convenient.

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