AstroCV

Anyone notice the lights stay on in the cabin after parking the car? Also noticed occasionally that the headlights will stay on after I park the car and leave it in the garage. I always make it a point to push the start/stop button to turn off the car but sometimes it seems that it takes the car being locked to shut everything down. I’m always paranoid that I am going to return to a dead car/12v battery.

hlothery

On the upper console, behind the rear view mirror, on the far right there is a button. When pushed, it turns red, and deactivates the interior lights from coming on, even if you open the doors. I have that button pushed to help mitigate 12v battery problems (he said, hopefully!) BTW, they don't stay on for long.

MBDrifter

The good news is that if the 12V drops below a certain SOC then the high voltage battery will recharge it.

superswiss

There are a few settings to control the interior/exterior lighting switch-off delay and locator lights. All explained in the owners manual on page 153 (exterior switch-off delay), 154 (locator lighting) and 156 (interior lighting switch-off delay), in other words read the manual.

hlothery

The way I understand it, this is only true if the vehicle is turned on....i.e.the on button is pushed. If the vehicle is turned off and something drains the 12V battery, you are screwed. This is the problem described on so many EV forums where owners experience 12V battery failure and the cars are bricked without a 12V booster charge.

MBDrifter

If the system is working correctly then the high voltage battery should always be able to charge the 12V. Without the 12V battery the HV battery would not be able to actuate the internal contractors and power up the vehicle. The 12V also controls the cell balancing that is needed for the HV battery. I think the reason some of the vehicles become bricked after the 12V dies is due to the HV battery not being able to close these contactors.

This happens a lot with hybrid cars that go unused. The 12V battery will die and then the HV battery follows.

StormingHabs

Having had a completely dead 12V battery while tinting and multiple critical warnings on subsequent days this is unfortunately not the case. For the 12V battery to charge the car must be running. it can be in Neutral and not move but the car must be turned on and only then does it charge the 12V battery.

W205C43PFL

Since the EQS no longer has an ICE, I wonder why they don't just enable the high voltage battery to charge the 12V battery... You know, sharing is caring. On MB's mild-hybrid vehicles, the 12V battery shares the power with the 48V battery via the voltage converter but vehicle has to be running. Why can't it be done for the EQS? Could it be that MB copy and pasted the code over to the EQS so the system behaves just like the ICE vehicles? Unless there are no (safe for normal use?) voltage converters that converts the high voltage battery to charge the 12V battery. I am guessing it is the latter?

StormingHabs

My understanding is that Tesla for example does charge the 12V battery when the system notices the charge getting low. No need to have the car running or plugged in, it just happens. Not sure why EQS isn’t working the same way as it seems obvious (to me at least) that letting the 12V charge off of the HV battery is a good approach.

superswiss

My understanding is that this is an issue with other EVs as well. It's been documented to be an issue on the Audi e-tron for example. I also just watched a video out of Germany yesterday about VWs latest software release for the ID models, and one thing they changed is to automatically charge the 12V battery if it gets low. However, current owners have to bring their ID to a dealership to physically replace the battery. Seems like its not just software, but also hardware. I'm guessing Mercedes is using the same supplier and they hadn't accounted for charging the 12V battery while the car isn't on. Apparently it has become a big enough issue for VW to change it and do a retrofit on existing cars.

hlothery

It does seem counterintuitive. The Taycan had a problem with this also. Hopefully it will be solved as the vehicle evolves, and they can retrofit a solution for us early adapters. In the interim, I will continue to minimize the drain on the 12V battery in every way I can, and drive the hell out of the car to charge it!

W205C43PFL

Good find, I wonder in the case of the EQS if the battery control module is the only thing that needs to be swapped instead of the entire battery?