Ever noticed your 2013 CLS 550 acting a little… peculiar? Maybe the ECO start/stop isn't working, or you’re getting strange error messages on the dash. Chances are, that tiny auxiliary battery hiding away in your car is the culprit. It's easy to overlook, but this little power pack plays a crucial role in keeping your CLS running smoothly.
This seemingly insignificant battery supports a whole host of essential systems in your W218, and when it starts to fade, things can get frustrating. In this article, we'll dive deep into the world of the auxiliary battery on your CLS 550, covering everything from its purpose and symptoms of failure to replacement tips and frequently asked questions. Let's get started!
What Exactly Does the Auxiliary Battery Do?
Unlike the main battery, which cranks the engine and powers the car's primary electrical systems, the auxiliary battery in your 2013 CLS 550 is responsible for supporting specific functions, particularly when the engine is off or during ECO start/stop events. Think of it as a backup system for critical components.
Here's a breakdown of its key responsibilities:
- ECO Start/Stop System: This is perhaps the most noticeable function tied to the auxiliary battery. When the battery is healthy, the ECO start/stop system seamlessly shuts off the engine at traffic lights or in stop-and-go traffic, restarting it instantly when you're ready to move. A failing auxiliary battery will often disable this system, displaying a message like "ECO Start/Stop Inoperative" on the dash.
- Electronic Gear Selector: This battery can act as a backup for the electronic gear selector. If your main battery dies, the auxiliary battery might provide enough power to shift the car into neutral, allowing it to be towed.
- Certain Control Modules: Some control modules, like those related to braking and safety systems, rely on a stable power supply. The auxiliary battery helps maintain this power, especially during periods of high electrical demand or when the main battery voltage dips.
- Backup Power for Critical Systems: In the event of a main battery failure, the auxiliary battery can provide a temporary power source for essential systems, allowing you to safely pull over and address the issue.
In short, it's a safety net and an efficiency booster, all rolled into one small package.
Uh Oh, Is My Auxiliary Battery Dying? Spotting the Warning Signs
Recognizing the symptoms of a failing auxiliary battery early on can save you from potential headaches down the road. Here are some common indicators to watch out for:
- "ECO Start/Stop Inoperative" Message: This is the most frequent and obvious sign. If you consistently see this message, even after driving for a while to charge the batteries, the auxiliary battery is likely the problem.
- Erratic ECO Start/Stop Behavior: The system might work intermittently, shutting off the engine sometimes but not others. This inconsistent performance is a telltale sign of a weakening battery.
- Warning Messages on the Dashboard: You might see other warning messages related to electrical system malfunctions, even if the main battery seems fine. This could indicate that the auxiliary battery is struggling to provide adequate power.
- Difficulty Shifting Out of Park (in rare cases): In extreme cases of auxiliary battery failure, you might experience difficulty shifting the car out of park, especially if the main battery is also weak.
- Overall Electrical System Glitches: Less common, but still possible, are general electrical glitches like flickering lights or intermittent malfunctions of other electronic features.
Important Note: Don't immediately assume the auxiliary battery is the culprit. Always check the main battery and charging system first. A weak main battery can sometimes trigger similar symptoms. A simple battery load test can help determine the health of both batteries.
Where is This Mysterious Battery Hiding?
Finding the auxiliary battery on your 2013 CLS 550 isn't always straightforward. On the W218, it's typically located in the trunk, but not necessarily in the same location as the main battery. You'll usually find it tucked away:
- Under the rear shelf: You might have to remove some trim panels to access it.
- Behind a side panel: Check the side panels in the trunk area, especially on the passenger side.
Consult your owner's manual for the exact location specific to your vehicle. Once you locate it, you'll likely find a small AGM (Absorbent Glass Mat) battery.
Replacing the Auxiliary Battery: A Step-by-Step Guide
While replacing the auxiliary battery is a relatively straightforward DIY project, it's crucial to follow the correct procedure to avoid damaging your car's electrical system. Always disconnect the negative terminal of the main battery before working on the auxiliary battery.
Here's a general guide:
- Gather Your Tools and Supplies:
- New auxiliary battery (ensure it's the correct type and size for your CLS 550)
- Socket wrench set
- Screwdrivers
- Gloves
- Safety glasses
- Memory saver (optional, but recommended)
- Locate the Auxiliary Battery: As mentioned earlier, consult your owner's manual to pinpoint its exact location.
- Disconnect the Main Battery: Open the hood and locate the main battery. Using a wrench, carefully disconnect the negative (-) terminal. Secure the cable away from the battery terminal to prevent accidental contact.
- Remove the Auxiliary Battery:
- Remove any trim panels or covers that are obstructing access to the battery.
- Disconnect the negative (-) terminal of the auxiliary battery first, followed by the positive (+) terminal.
- Remove the battery hold-down clamp or bracket.
- Carefully lift the old battery out of its tray. Be mindful of its weight and any acid residue.
- Install the New Auxiliary Battery:
- Clean the battery tray and terminals with a battery terminal cleaner.
- Place the new battery into the tray, ensuring it's properly aligned.
- Secure the battery hold-down clamp or bracket.
- Connect the positive (+) terminal of the auxiliary battery first, followed by the negative (-) terminal.
- Ensure the terminals are securely tightened.
- Reconnect the Main Battery: Reconnect the negative (-) terminal of the main battery.
- Test the System: Start the engine and check for any warning messages on the dashboard. Test the ECO start/stop system to ensure it's functioning correctly.
- Dispose of the Old Battery Properly: Take the old battery to a local auto parts store or recycling center for proper disposal.
A Word of Caution: If you're not comfortable working with electrical systems, it's best to have a qualified mechanic replace the auxiliary battery. Incorrect installation can damage your car's electronics.
Choosing the Right Auxiliary Battery: Specs and Considerations
Selecting the right auxiliary battery for your 2013 CLS 550 is crucial for optimal performance and longevity. Here are some key factors to consider:
- Battery Type: The auxiliary battery in your CLS 550 is typically an AGM (Absorbent Glass Mat) battery. AGM batteries are designed to withstand frequent charging and discharging cycles, making them ideal for applications like ECO start/stop systems.
- Voltage and Capacity: Ensure the replacement battery has the correct voltage (typically 12V) and capacity (measured in amp-hours, Ah). Consult your owner's manual or the original battery's label for the recommended specifications.
- Physical Size: The replacement battery must fit properly in the designated battery tray. Measure the dimensions of the old battery to ensure the new one is compatible.
- Brand and Quality: Choose a reputable brand known for producing high-quality batteries. While cheaper options might be tempting, investing in a reliable battery will save you money in the long run. Consider brands like Bosch, Interstate, or Optima.
- Warranty: Look for a battery with a good warranty. This provides peace of mind and protection against premature failure.
Preventing Future Auxiliary Battery Woes: Tips for Longevity
While auxiliary batteries have a limited lifespan, you can take steps to extend their life and prevent premature failure:
- Regularly Check the Main Battery: A weak main battery can put extra strain on the auxiliary battery. Ensure your main battery is in good condition and properly charged.
- Avoid Short Trips: Short trips don't allow the auxiliary battery to fully recharge. If possible, take longer drives occasionally to ensure it gets a proper charge.
- Minimize Electrical Load When Idling: Avoid using excessive electrical accessories (e.g., headlights, air conditioning) when the engine is idling or during ECO start/stop events. This reduces the load on the auxiliary battery.
- Use a Battery Tender: If you frequently leave your car parked for extended periods, consider using a battery tender to keep both the main and auxiliary batteries fully charged.
- Consider a Battery Monitor: Install a battery monitor that displays the voltage of both batteries. This allows you to track their health and identify potential problems early on.
Frequently Asked Questions
- How long does an auxiliary battery typically last? Auxiliary batteries typically last between 3 to 5 years, depending on usage and environmental conditions.
- Can I drive my car with a dead auxiliary battery? Yes, but the ECO start/stop system will likely be disabled, and you might experience other electrical system glitches.
- Is it necessary to replace the auxiliary battery at a dealership? No, you can replace it yourself or have a trusted mechanic do it, as long as you follow the correct procedure.
- Will replacing the auxiliary battery fix all electrical problems? Not necessarily. It will fix issues specifically related to the auxiliary battery's functions, like the ECO start/stop system.
- How much does an auxiliary battery typically cost? Prices vary depending on the brand and type, but you can expect to pay between $100 and $300 for a quality AGM auxiliary battery.
- Does the auxiliary battery need to be programmed after replacement? No, the auxiliary battery does not require programming after replacement on a 2013 CLS 550.
- Can a weak auxiliary battery affect the main battery? Yes, a weak auxiliary battery can place additional strain on the main battery, potentially shortening its lifespan.
In Conclusion
The auxiliary battery in your 2013 CLS 550 might be small, but it plays a significant role in the car's overall performance and reliability. By understanding its function, recognizing the symptoms of failure, and following the proper replacement procedure, you can keep your CLS running smoothly for years to come. Don't neglect this often-overlooked component - a healthy auxiliary battery is key to enjoying all the features your CLS 550 has to offer.