Radman991

I recently left my car for relatively long term storage over the summer. It was charged to 80% and has dropped 2% SOC in the last 3 weeks. I left the car unplugged sitting in my air conditioned garage in Florida. I have been monitoring its status with the Mercedes me app. Today I got the message the 12v battery is partially charged. I was under the impression after reading multiple posts in the forums that a trickle charger on the 12 v battery wasn’t necessary. I summer in RI so I don’t have immediate access to the car. I am concerned if I don’t do anything the 12v battery will run down to the critical level and then won’t be able to start the car.
Any thoughts members ?? should I just put a trickle charger on or is there some other concern about the health of the battery. I will say the car was built in July 22 and delivered to me in mid December.

Utopia Texas

How often are you “monitoring” the car? Every time you do so the system uses the 12v battery to check the readings and communicate through the app. The 12v battery is very small.

MB needs to change the set up where the small 12v battery is charged by the larger driving batteries even when the EQS is not being used. The small 12v battery going empty appears to be a problem across other brands also.

Radman991

I probably open the app up once a day to just look at the status of the car, ie charge status. I didn’t think by just opening the app and looking at the various options that it would affect the battery. For example I opened up the app and hit the service button and saw that it said 12v battery was partially charged, previous reading had been charged. Is this using some of the 12v battery to do this?
I haven’t done anything that would actually change the state of the car like lock or unlock it.

Utopia Texas

I believe the 12v does everything except move the vehicle. Lights, horn, door locks, AC blower etc. Batteries can be finicky. Probably nothing you are doing. The battery may just be past it’s prime though it is relatively new.

hlothery

How long has it been sitting? If it is months, then you definitely need a trickle charger on the 12v battery, IMHO, and someone hired to go in periodically and charge the high voltage batter up to more than 50%.

Radman991

It’s been sitting for 3 weeks. I had planned on letting it sit for the summer. I was under the impression Mercedes does not want you to open the frunk or attach a trickle charger so I didn’t do that. I’m at my dealer up north now seeing what they recommend. It has plenty of charge on the high voltage batteries, currently at 80%.

Radman991

Went to my dealer today and explained my situation with the car 12v battery and got some helpful info. Got the service manager involved. First thing they recommended was to attach a trickle charger despite Mercedes advising not to open the frunk. Second option was to precondition the cabin thru the app so that a/c turns on. They felt that by turning on the compressor which is powered by the high voltage battery that would also charge the 12v battery. As I was leaving the dealership the service manager approached me and said he had more information. Apparently with the ignition off and engine off for a very long non-operational time (as they describe it) buck mode can be requested by the SAM-driver on- board electrical system control to recharge the 12 v battery. ( I’m quoting from the print out he gave me). So they felt that the car should detect the low voltage and recharge it without me having to do anything.
He did say that making inquiries thru the app to check the status of the car most likely does put a strain on the 12v battery, so I will stop looking at my SOC and my tire pressure like I have been doing.
Another interesting fact I was told was that the latch that opens the frunk has been removed on the new EQ cars that have been arriving lately, another way for Mercedes to stop customers from opening the frunk.

I hope they are right. I will occasionally monitor the car to see if the status of the 12 v battery changes.

Utopia Texas

This will be a interesting story to follow. Please give us updates as time passes….

Wolfaltman

Where is the latch to open the frunk? Pictures or specifics.

Radman991

It’s located in the same location as are all front hood release latches on most cars, in the drivers side where the OBD socket is located. On the EQS there is a cover switch over the latch. Some models came thru with a small screw on the cover. I’ve never opened mine but I did locate one time and I don’t think mine had a screw.

Crito

I learned about it from this video:

finlayson

Check again in a day or two. You'll probably find that the 12V battery is fully charged once again. (This is what has happened to me whenever I leave my EQS (580 SUV) unattended for a few weeks.) Apparently the vehicle periodically uses the main battery to recharge the 12V battery, automatically. As long as your main battery has enough charge, you don't need to do anything to keep the 12V battery charged.)

Radman991

I checked today. You are correct. It now says it’s fully charged.

Utopia Texas

Where in the app does it show anything about the 12v battery? I’ve looked everywhere but don’t see anything. Thanks…

finlayson

From the main menu, click "More", then click on the "Service" button (the one with a wrench icon). This will show you the status of the 12V battery (and also brake and washer fluid).

Utopia Texas

Ok… Thank you

vhooloo

Unfortunately, I got battery critical error message on my 2023 EQS 450 and it stayed that way for 4-5 days and was never charged by the main battery. Finally decided to get the lemon towed to the dealership this morning.

Sunbeltgolfer11

WE have two cars in the garage with battery tenders hooked up. The SL550 is hooked up with a pigtail to the trunk battery and the E63s is attached to the posts under the hood. I've been checking them a few times a day since I saw this thread. They are occasionally warm, but, never hot to the touch.

Diesel Benz

I guess the "battery critical" error message was for the 12 V battery, not for the high voltage battery? There should not be any need to tow the car once the 12 V battery is low, just when it is completely flat. Or did it get completely discharged during the 5 days waiting.

Anyway, it gets confusing if a MY 2023 car fails to charge the 12 V battery, one could assume all the SW being sufficiently up-to-date.

Diesel Benz

What are you after, are you saying the battery tender gets hot, the connector to the battery or the car? Not clear as the thread so far did not mention anything getting hot (that I had noticed).