Mercedes EQC and High Voltage Battery Failure. Auto transporter? It was enough ... to look under the hood [Reader] • CARS

We've been trying to write this tip for a month, but we needed a good example. Here. Our reader has a Mercedes EQC. One day he was greeted with the message “High Voltage Battery Failure”. The information was a little scary, and the solution turned out to be trivial: charging a 12V battery.

Got an electric car? Take care of the 12V battery

In an electric car, there are only two things that wear out faster than an internal combustion engine. Firstly, there are tires: those on the drive wheels can lose rubber at an alarming rate, especially with a driver who likes to test electricians with high torque 😉 Therefore, it is worth checking the condition of the tread and, if necessary, changing the wheels.

The second, surprisingly, is a 12V battery.... He may refuse to comply (check out) after a few months or a year, which will lead to a number of strange, unusual and frightening mistakes. Here is the story of our Reader who bought a Mercedes EQC in March this year:

After about three months of use and having driven about 4,5 thousand kilometers, I get into the EQC in the garage, press the button Homeand a big red message “Failure of the high-voltage battery».

Of course, turning the machine on and off did nothing. Quick connection to Mercedes center (button above rearview mirror), remote diagnostics and solution: a car for a tow truck, and a replacement for me.

Since the tow truck was supposed to arrive in a few hours (there was no rush), I opened the hood of the "engine" compartment for the first time. There I saw typical Mercedes battery charging points. I started looking through the manual (678 pages), but I found one sentence about the low voltage battery: "The battery should be replaced by an authorized service station."

Mercedes EQC construction diagram. The 12V battery is located on the right for left-hand drive vehicles (1) or on the left for right-hand drive vehicles (2) (c) Daimler / Mercedes, source

However, I decided to give it a try. The charger was connected as in a conventional internal combustion car. The machine informed me that the 12 volt battery is really empty. After about 3 hours of charging, the EQC came to life.... Everything worked fine. Although the car crashed on its own in a tow truck, it was taken into service. After checking everything was OK.

My guess is that I ran into a software bug that was preventing the small battery from being charged. The mechanics downloaded the update and everything has been working fine since then. One of them, when asked about the reason, jokingly said that I must have been turning the starter for too long ...

Application? It's a shame that the EQC system can't catch such a simple malfunction. A similar case recently occurred with the Volkswagen ID.3 [but it can happen with other models - approx. editor www.elektrowoz.pl].

To summarize, if we have an electrician and don't travel long distances, it doesn't hurt to fully charge the 12V battery when the temperature drops to about 10-15 degrees. At the same time, we, as the editorial team, do not recommend Bosch C7 chargers, they can be damaged by lying in the cabinet (microswitch problem).

> Kia e-Niro is off but one of the blue charging LEDs is still flashing? We translate

As far as the Mercedes EQC is concerned, we have a longer history of buying this model. It will appear on the pages from day to day 🙂

Introductory photo: Mercedes EQC (c) Mercedes / Daimler construction diagram

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