If you are stuck with a dead 12 V battery, you have to call a qualified tech for help, or else.
Finding out your 12-volt battery is suddenly dead is often no big deal for car owners, a jump start from a neighbor or a battery pack is all you need to go about your day.
That reality is not so for Mercedes EQS owners with their $100,000 electric cars.
Mercedes EQS owner and MBWorld.org Forum Member StormingHabs recently dropped off his EQS to get the windows tinted. During the process, he received notifications from his Mercedes App that his starter battery was getting critically low.
In fact, it died shortly after.
Although electric cars have a larger battery for its traction motor, they still need a 12-volt battery, like a regular gas car, to run lights, windows, wiper motors, fans, A/C, the heater, and your infotainment system.
Here’s where the 12-Volts are located on the EQS. The primary 12-Volt is in red and the back-up 12-volt, included with certain options packages, is in green.
Like most cars, electric cars included, the 12-volt battery is charged when the engine (or traction motor) is on. If the window tint specialists had the EQS in the ON position instead of accessory mode, the 12-volt battery wouldn’t have drained to critical levels. But, how could you fault them when even Habs himself didn’t know to leave a note instructing the tint people to do so.
As Habs soon realized, he could not tell the tint window people to just jump start it.
Because, as I explained in a previous blog post, EQS owners aren’t allowed to open their own hoods where the 12-volt battery happens to be.
Long story short, there are no serviceable parts under the hood of an EQS and, if you poke around your infotainment system to find info about the hood, there are instructions saying only specialists should open it.
There is a hood latch under the driver’s side dashboard, but, only a Mercedes Tech is technically allowed to pop it open while your EQS is under warranty.
The EQS comes with a four-year/50,000-mile basic warranty and a 10-year/155,000-mile powertrain warranty.
To complicate things even further, a dead 12-volt battery on an EQS means you cannot turn on/off the electric parking brake, the drive system can’t be started, and you can’t shift into Park or Neutral.
A dead 12-Volt battery means a flat bed tow only.
“Spoken to multiple dealerships and the consistent message is that you should NOT “jump start” the car as it can lead to damage,” Habs mentioned in his update.
“I was warned by a Mercedes tech that if I do it myself, I could potentially void the warranty. While I don’t see how that could possibly be the case, it did make me hesitate.“
His EQS essentially bricked itself.
“It’s currently plugged into the emergency 110V charger on suggestion from a service tech, and a flatbed is on the way to take it to the dealer. I suppose this is the downside of buying a brand-new generation of car, seem to be a lack of knowledge amongst the dealerships on how to handle failures.“
“Flatbed eventually showed up, and the guy DID hook up a battery charger to jump start it (since he was sent by Mercedes I guess it was OK) and sure enough, the car started right up. A few things didn’t work such as windows wouldn’t go down/up, seats wouldn’t move, but I was able to drive it. We took it on the flatbed to the dealership, and they asked me to drive it for 20-30 minutes, which I did, and now it’s like it never happened.“
Habs experience aligns with what it says in the EQS owner’s manual. In all instances for EQS 12-volt battery starting and charging assistance, you should, “Only have starting assistance and battery charging provided by a qualified specialist workshop e.g. an authorized Mercedes-Benz Center.”
Here’s what it says.
Lucky for Habs, a Mercedes qualified tech was nearby to legally pop the hood and jump start his EV.
But, what if you’re halfway to Vegas and, for some reason, you get a dead battery in the middle of nowhere at 3 a.m. and no qualified Mercedes tech is even awake or within reasonable driving distance?
What are you supposed to do, then?
This isn’t a problem for most electric cars like a Tesla where a jump pack, something most tow trucks carry, will get you on your way or a Nissan Leaf (MSRP $27,400) where jump-starting is as easy as a gas car.
So, why is it such a problem on a six-figure Mercedes EV?