So every couple of weeks get this message from the Mercedes Me connect app saying the 12v battery is low, while the car is parked.
Then I get to the car, turn it on and no message on the dash. Is this a software glitch or a defective battery?

 

You can buy cheap voltmeters which plug into the cigarette lighter socket. Maybe get one of those and monitor the battery voltage every morning?

 

My battery really wants to complain today.
Is the starter battery the 48v or the 12v?
Good thing I'm taking the car to dealership next week for the fuel pump recall.

 

Depending on how often you drive the car, this is not necessarily unusual. My 2019 C63 is fairly low mileage at about 4000 miles annually and my battery tends to be low, however I don't really get these alerts unless the car is in service and they are working on it with the doors open and such and draining the battery. I usually get them quickly, though. Because these cars maintain a constant data connection for Mercedes me and the telemetry, they don't fully shut down while parked and always consume power.

I've recently started to get some weird electrical problems with the digital instrument cluster losing its settings and such. I have a hunch that it is the battery. My kinda cheapo battery tender I've been using has indicated that my battery is bad, but it's not giving me much else. I have an appointment for next week to take it in, but decided to first upgrade the charger to a more sophisticated charger from Juice My Ride. It just arrived today and it's currently charging. It has an automatic repair mode and more sophisticated automatic charging program, so I'll see what it does. When I plugged it in, it showed that my battery only had a 20% charge and was at 11.6V. My old charger never gave me any of that information. The voltage started to quickly ramp up and it was showing the charge level going up as well.

Point is without knowing the health of your battery it's only a guess what's going on. I'd recommend you also get a good battery charger or at least a battery meter as suggested above so you know what the state of charge actually is. If it's low as in my case then you know what's going on and you need to charge it.

Here's the charger I got. They used to resell the OEM CTEK charger, but now have their own branded charger.

https://www.juicemyride.com/collecti...attery-charger

 

Quick update FWIW. The new charger fully charged my battery w/o an issue in AGM mode, so I'm thinking my other charger has gone on the fritz. Really like this new one so far. The instrument cluster hasn't lost its settings and the car's been sitting over a week since I last drove it, so I have a hunch that the battery just got really low. Now that I can see exactly the charge level of the battery, I can keep a better eye on it. Probably will cancel my appointment for next week, unless something happens between now and then. They shipped very quickly, too. I ordered the charger on Wednesday and as said it arrived today.

 

I'm getting the "battery is low/critical" message.
I drove the car Friday.
I went away for a few days, not back until tomorrow night.
Today is Tuesday.
I've gotten several messages on my phone that my battery is low/critical.
How is this possible?
The weather where the car has been is about 60 degrees.
This is a new car which was purchased last summer. 2023 C300.

 

The MB dealership where I bought my car currently lists an inventory of 263 vehicles. I wonder how they keep all the batteries maintained until sold. Or maybe they just connect a battery reconditioner over-night before customer delivery.

 

Do you leave the key in the vehicle? If so, that's probably why. It happened on mine once and then never came back.

 

Absolutely not. The keys are in my home.

 

I have my car at the dealership right now for the fuel pump recall and asked them
to check on the battery errors.
this is the message I just received from my service advisor

 

This was the result...

I got home last night.
App said remote wouldn't work and battery was discharged.
I hit the remote and the car did open.
I was able to turn the car on. It said i should keep the ignition on to charge the battery.
I went for about a half hour drive.
All seems to be ok.
Not sure what to make of all this.

 

Guys this car is always connected to Mercedes servers. That means that if you have the car in the parking place for long this message will appear in all your apps

as the battery will be drained. What you have to do once the car is parked is to activate the standby option, that allows to disconnect your car and leave it with no options of connection.
Mind you, if the car doesn’t have the battery fully charged you won’t be able to activate it.
We didn’t get a car, it’s like a robot sending data permanently.

 

No, it has to be something different.
I never have the car parked and locked for long. I drive an average of 50 miles per day, mostly highway so the battery should be recharging.
The two times I left for a week my car had been parked in my garage, open, and no critical battery messages on those instances.
So far I got the low/critical battery alerts an hour or two after I turn off the car. Then when I get home I connect the battery to a slow charger overnight and I won’t receive those messages for a couple of weeks.

 

In another forum, a member reported that he had been leaving his key fob overnight on his kitchen counter, which just happened to be on the opposite side of the wall separating the garage, and less than 20 feet from his car. That was close enough to cause a problem.

 

so I just picked up my car from the dealership and they updated/reprogrammed the doors’ control modules. There’s a MB bulletin highlighted but I wasn’t able to look it up online though.
Let’s see wether in the next couple of weeks the battery issue comes back.

 

I found someone on the W206 C63 forum had the same issue
https://mbworld.org/forums/c63-amg-w...an-2023-a.html

TSB li54.10-p-076820

 

Just an update on this issue.
I've been getting those error messages at times and I just took the car to get it inspected, again.
The dealership performed another update, part of the same TSB LI54.10-p-076820. This time it's the version 7 of the update, dated June 2024.
Let's see if this fixes this annoying problem.

 

I had the same problem with my 2019 A250 in winter. I also concluded that infrequent driving contributed. Started using a trickle charger with some limited success.

Debugged by checking off line battery voltage. If I parked with voltage >12.7 (100%) it would drop by 0.2v per day. From 12.0 v took trickle charger 3 days to recharge. Eventually, trickle charger would not fully charge the battery.

I complained to dealer and he replaced the dying battery after 3.5 years. I said that seemed unreasonably short as my experience with batteries on today’s power hogs (Lexus, Acura, Infiniti) was 5 years. They gave me the new battery as a ‘goodwill gesture”.

For this winter I’m going to use a more sophisticated battery charger as described above.

P.S.: The first sign of this is when the auto start/stop no longer activates.

Perhaps if Mercedes used higher capacity batteries this would be less of a problem. However, I can’t find a 3rd party higher capacity battery that fits.