Has your Mercedes been exhibiting any of the following signs recently?
#1- “Auxiliary battery malfunction” warning on the dashboard.
#2- Unusual behavior by Lane Keeping Assist, Blind Spot Assist, etc…
If yes, it appears that your Mercedes' auxiliary battery has given up. So, what exactly does this auxiliary battery do in your vehicle, and how its failure can affect the overall operation of your vehicle's electrical system? This blog post explains it all.
Mercedes Auxiliary Battery: How Is It Different From The Primary Battery?
If it is to be put in a nutshell, the auxiliary battery is more of a backup to the primary battery of your Mercedes. Among other things, it ensures that the power supply to major electrical components of your vehicle, such as the various systems of Mercedes' driver assistance packages, does not fluctuate when starting/stopping the engine. In some Mercedes models, capacitors are being used as an auxiliary source of power.
A part of such importance, if malfunctions, will contribute to all sorts of drivability problems in your Mercedes. The list below covers some of the prominent reasons behind auxiliary battery failure in Mercedes cars. Also, as you read through you will discover some proven solutions to this problem.
Mercedes Auxiliary Battery: What Leads To Its Failure?
Reason #1- It has gotten old
Just like the primary battery, your Mercedes' auxiliary battery has an age capping. You can use your vehicle's battery up to a limit and for most car batteries that limit is within the three to five-year range. As your Mercedes' auxiliary battery ages, it loses its ability to hold a charge. And, there will come a point after which it will not be able to hold any charge. It is therefore advised that you get your vehicle's auxiliary battery tested periodically; especially if it is old.
What to do if your Mercedes’ auxiliary battery is old?
- Conduct volt tests on your vehicle’s auxiliary battery periodically.
- If it happens to you that it has reached its maximum serviceable life, it is better to replace it.
Reason #2- Defective charging system
Like the primary battery, your Mercedes' auxiliary battery depends on the charging system to obtain the required amount of power - so that it can do the job it is designed to do. If there is something off with any part of the charging system – whether it is the alternator or the voltage regulator – both the primary battery and the auxiliary battery will suffer. So if your Mercedes' "Auxiliary battery malfunction" message is flashing and you're noticing electrical anomalies, check the charging system.
What to do if your Mercedes’ charging system is faulty?
- Check each part of your Mercedes' charging system individually.
- If any fault is detected, get it repaired by a trusted technician.
Reason #3- Battery management system is defective
Another explanation behind your Mercedes' auxiliary battery failure is that the battery management system that is tasked with looking after it has failed. Among other things, the battery management system oversees and regulates the charging and discharging of the auxiliary battery. If it is not functioning the way it is supposed to- because of a technical glitch or some other reasons, the auxiliary battery's charge-holding capacity may get adversely impacted.
What to do if this is the case?
- Check if there is everything fine with your Mercedes’ battery management system.
- If something seems wrong with it, it would be better to contact your mechanic to fix the problem.
Reason #4- Flat primary battery
If the main battery in your Mercedes has gotten weak, it can put a strain on the auxiliary battery. It is therefore advised that you check on your vehicle’s primary battery from time to time and if it has reached its maximum serviceable life, get it replaced.
To Sum Things up…
From a weak primary battery to a defective battery management system; there are all sorts of reasons why your Mercedes' auxiliary battery may fail. In any case, if your Mercedes' "Auxiliary battery malfunction" message is on or you are noticing unusual electrical anomalies, you better reach out to the nearest service center to get the issue diagnosed and repaired. Because if you don't, you may end up with costly repairs.
About the Creator
Automotive Andres is one of the leading luxury European automotive repair and service facilities located in Chicago. We have years of experience in looking after high-end cars like Audi, BMW, Jaguar, Land Rover, Mercedes Benz, Mini.