Forgive me if this has been asked and answered, searched and couldn’t find an answer. Been getting the Battery Critical message consistently… told by the dealership that I’m not driving it enough. Asked about putting a trickle charger on the car and was told that the battery is in the trunk and it’s not feasible to do it. Very confusing.. I have read threads here where others have put chargers on their cars. Does anyone mind telling me where they put it and what is recommended?

 

First thing to check would be that your car isn't fully shutting down in a timely fashion, or at all. After driving you need to lock it and then you want the fob out of contact with the car; either get it far enough away (mine can see the car through the walls for 50 feet) or bag it. If you do this and the problem goes away you're one of a great many, if not and it really is short trips with little charge time you'll find the charge points under the hood. If you haven't already, download the pdf from https://www.mbusa.com/en/owners/manuals, and navigate to page 430.

You may want to consider having that pdf on your phone for the inevitable questions; it's the fastest way to find SDM (some damn thing) while out and about.

 

Thanks so much for your quick reply… how far away with the key FOB is far enough Mine is kept approx 100 feet away. So fed up w my dealership not thinking this is a legitimate problem and telling me my battery contacts are in the trunk to charge the battery. My husband is really nervous about messing w things under the hood so trying to do my own research on this

 

I had to get a Faraday bag to keep the fob in, so it was not constantly detected. Have no idea why but it helped the battery drain and stopped the notices. I wanted to put it in standby mode as it stays parked for long times but that is disabled (greyed out) because the "battery is not sufficiently charged to activate standby mode" even though it was on a battery tender and the indicator light says fully charged. I suppose something electronic is indicating low battery level despite a full charge. This was a MB screw up IMO.
This works great:

 

Thank you so much! That’s exactly what mine is doing. Appreciate the link .. I will def try that

 

That's what I meant by bagging it, it's easier than getting distance. You can also turn the fob off and back on, but that's also more hassle than bagging it. Hard to say how far you have to go to get it out of range since you have obstructions, and the materials of said obstructions, in the equation. At the apartment I don't need to do anything, lots of cement and distance tween the two. At the house I bag it, it can see the fob through a good chunk of the house.

 

Yes, I use the CTEK Battery Tender... it's been a wonderful solution, since I don't drive my S-Class as often as needed to keep the battery happy. See previous post here:

https://mbworld.org/forums/s-class-w...ml#post8607555

It's true that the battery is located in the trunk... BUT, you don't need to access the trunk, since you use the battery jump terminals under the hood. The positive terminal is hiding under a red sliding cover with a "+" on it. There's a ground post nearby, for the other cable.

Hope that helps!

 

I just traded in my 2022 S500... In the two years I had it i got the low battery message 4 times on Mercedes Me App.... each time I used my CTEK to charge it via the engine compartment....

I found that most times I had a issue was when I didn't lock the car immediately.... Once after a very long drive which confused me....

 

Have been getting same battery messages and dealer answers. We lock it in garage and haven't seen another battery message!

 

The posts from crabman and Mercedes buff are ‘right on’. Mine is a 2021 and I also had the issue you are experiencing. I solved it with the CTEK trickle charger connected on the passenger side of the engine bay and was advised on this forum that if I push the lock control on the key fob twice the car will honk twice to confirm the double push and will not communicate with the key fob, thus not using the battery. You will have to press the open on the key fob to unlock the car, it will not extend handles when you approach the car.
I drive very short distances and use the trickle charger about every month on a weekend day just to assure the battery keeps at the optimum level. You will be able to determine how often you need to use the trickle charger by how long it takes the charger to green.
Using the double click on the key fob and the charger has eliminated the ‘critical battery’ warning. It’s now been over a year since I started that.

 

Had same critical low issue, and dealer said it needed a software update. Been fine ever since. This was about 3 weeks ago……..

 

Good to hear it is resolved.

 

I just had the 12V battery warning on the app. I recently had my yearly service done and mentioned it to my dealer and he said to ignore the app message but pay attention to any in-car warning. The app was recently changed to trigger a warning at 75% and ever since then they’ve been flooded with concerned calls. They’re trying to get Mercedes to change it back to whatever it was.

Also, I’m really curious if the 48V battery affects the recharge rate of the 12V battery since it’s a DC-to-DC charging system. The ISG charges the 48V battery while the 12V is charged from the 48V, or so I assume. I wonder if a low 48V battery, due to spirited driving for example, hinders the 12V battery charge.

 

Another trick is to press the lock button on the key fob twice when you lock your car. I use this when I'm on vacation and thus away from the car for weeks at a time. This does a couple of things, but one thing it does is stops the communication between the fob and the car, thus saving battery drain in both the car and the fob. One downside to this method is you must unlock the car with the fob the next time you approach; the door handles will not present when you walk near.

 

This. Just keep in mind the sequence has changed starting 2023 model year due to possibly complaints about keyless not working with possible causes such as this feature activating by accident or in the pocket.

 

For model year 2023 and beyond https://www.mercedes-benz.ie/service...-key-function/
Hold lock then double press unlock while holding lock at the same time.

 

I have a '21 S580 and finally solved my low/critical battery warning on the MercedesMe app--as well as never being able to put the car into stand-by mode since I've owned it (1+ year). The MB techs came up with a battery fault code a couple of times, but the battery itself tested fine, so they just reset the code (duh!). I finally convinced the service manager to simply replace the 12 V battery under warrany and like magic all the problems have gone away. No low battery messages, and I can always go into standby mode without getting the message that the battery has insufficient charge.

I drive mostly off-highway...generally for a minimum of 1/2 hour or so....but I tend to park the car for an hour and play with the electronics and sound system (a lot)...just running the battery down. But now by the time I drive back home, I'm fully charged and it stays that way. I started putting my keys into a little Faraday box I bought on Amazon in an attempt to address the low battery issue myself, but I'm not sure I need to do that anymore. The remote is always within range of the car when parked. BTW, my remote will work from over 1/3 mile line-of-sight, not sure why it needs that kind of range.

 

I've lived with this battery issue for the last two years of owning the car and thought that is the norm until my Parktronic start malfunctioning. I brought it to another dealership in my area and they were able to fix not only the Parktronic but the charging issue as well. They said something about the polarity of the battery was causing the issues so they replaced it and its been two months now and everything still working great. I have no more charging issue, and I even tried to replicate the problem and unable to. For example, when I handwash my car, by the time I'm done drying, it will pop up with low battery, charge now, it doesn't do it anymore. Second, If I don't drive it for 2-3 days, it will drain the battery, its not happening anymore. Third, Unless I drive it for a couple of hours or charge the battery, it will not let me put it in standby mode, now I can do it anytime. I really thought that this car is a POS but since the battery issues has been resolved, its a great car after all. Now, would I buy another Mercedes here in Europe! Hell No!

 

I would had thought that positive experience (afterwards) would had make you consider the brand again.

 

Well, there's more ongoing battle I have with them. Some are petty and others are just plain out wrong. First, I renewed all of my subscription and bought the video streaming as well. I even asked them first if my car was compatible with the video streaming. After I renewed, I called them again and asked, how do I use the video streaming since I only have YouTube on my system. They tell me that the system will be updated in couple of weeks, or I can go to a dealer and pay a fee to install it. I cancelled the video streaming subscription after the statement. Not only MB cancelled the video streaming, they also cancelled the entire entertainment package and uninstalled YouTube which I use. I had to renew the entertainment and had to reconfigure it which is not that hard but time consuming and annoying.

The second and still ongoing with MB is my extended warranty. My factory warranty is only two years, so I bought an extended warranty when I initially bought the car. Fast forward to 23 months later, I get an e-mail that my warranty is about to expire on 23 Mar 2025. So, I called my dealer and asked if I have to do anything to activate the extended warranty and says no, everything is good that the new warranty will take effect on 4 April 2025. I told them I find it weird that my factory warranty ends 23 Mar 2025 and my extended warranty starts 4 April 2025. My dealer said, its good on their end so there's nothing to do. So, I called MB and asked them why there's a gap on my warranty and they told me I have to get with my dealer if I wanted it changed. After two weeks of no response from my dealer, I went back to another dealer and they were very helpful. They explained to my what happened wrong. The explanation is the dealer should have asked me for when I registered the vehicle and asked for a copy then sends it to MB to reflect it as the new expiration of the warranty. Mind you, I picked up the car 19 Apr 2023 and registered the car on 30 Mar 2023. So, I sent MB and the dealer an e-mail requesting to change the date of my warranty along with the copy of my registration, warranty card and vehicle data form. Then two weeks later, MB tells me they will not honor my request because I'm a customer not the dealer. I told MB on the phone that my dealer is not responding so they said, fine we'll take care of it but we'll still have to get permission from Stuttgart. Couple days later, they came back and said, I need to go back to my dealer and have them e-mail. I called and e-mailed until I finally found someone to beg and plead to resend my initial e-mail and she did. Finally, it was changed to reflect my factory warranty to 30 Mar 2025. I still don't have a new warranty card reflecting 31 March 2025 as the start of the extended warranty.

I had many issues with MB, the dealership where I bought the car and the MB shop that serviced my car. Luckily, I found another dealer that is very good and able to solve all my problems. My recent success with the new dealership is not enough for me to continue with the brand.

 

Well, there's more ongoing battle I have with them. Some are petty and others are just plain out wrong. First, I renewed all of my subscription and bought the video streaming as well. I even asked them first if my car was compatible with the video streaming. After I renewed, I called them again and asked, how do I use the video streaming since I only have YouTube on my system. They tell me that the system will be updated in couple of weeks, or I can go to a dealer and pay a fee to install it. I cancelled the video streaming subscription after the statement. Not only MB cancelled the video streaming, they also cancelled the entire entertainment package and uninstalled YouTube which I use. I had to renew the entertainment and had to reconfigure it which is not that hard but time consuming and annoying.

The second and still ongoing with MB is my extended warranty. My factory warranty is only two years, so I bought an extended warranty when I initially bought the car. Fast forward to 23 months later, I get an e-mail that my warranty is about to expire on 23 Mar 2025. So, I called my dealer and asked if I have to do anything to activate the extended warranty and says no, everything is good that the new warranty will take effect on 4 April 2025. I told them I find it weird that my factory warranty ends 23 Mar 2025 and my extended warranty starts 4 April 2025. My dealer said, its good on their end so there's nothing to do. So, I called MB and asked them why there's a gap on my warranty and they told me I have to get with my dealer if I wanted it changed. After two weeks of no response from my dealer, I went back to another dealer and they were very helpful. They explained to my what happened wrong. The explanation is the dealer should have asked me for when I registered the vehicle and asked for a copy then sends it to MB to reflect it as the new expiration of the warranty. Mind you, I picked up the car 19 Apr 2023 and registered the car on 30 Mar 2023. So, I sent MB and the dealer an e-mail requesting to change the date of my warranty along with the copy of my registration, warranty card and vehicle data form. Then two weeks later, MB tells me they will not honor my request because I'm a customer not the dealer. I told MB on the phone that my dealer is not responding so they said, fine we'll take care of it but we'll still have to get permission from Stuttgart. Couple days later, they came back and said, I need to go back to my dealer and have them e-mail. I called and e-mailed until I finally found someone to beg and plead to resend my initial e-mail and she did. Finally, it was changed to reflect my factory warranty to 30 Mar 2025. I still don't have a new warranty card reflecting 31 March 2025 as the start of the extended warranty.

I had many issues with MB, the dealership where I bought the car and the MB shop that serviced my car. Luckily, I found another dealer that is very good and able to solve all my problems. My recent success with the new dealership is not enough for me to continue with the brand.

 

Sorry to hear that : (

 

Can an E53 48V battery trickle charge the 12V battery or would I need a trickle charger for the 12V? From what I have read, a BMW IX or i5 can charge the 12V battery through the 48V battery, but I haven't been able to find if Mercedes plug in hybrids have a voltage converter for 48V to 12V charging.

I have a CTEK One trickle charger. It uses a different connector than other CTEKs so I'm not sure if I can have dedicated wires directly on the battery. Having the trickle charger connections in the trunk like @cruise2024 would be more convenient than using the jump charge terminals under the hood. So that is a great suggestion.

 

Short answer, it would not.

Long answer: On an MB, 12V can help charge the 48V battery via a voltage converter when engine is on but it can't go backwards.