Passive safety: Mitigating the consequences of accidents with modern technology and the EQC-specific safety concept

Sep 4, 2018

When it comes to passive safety too, the EQC (combined power consumption: 22.2 kWh/100 km; combined CO2 emissions: 0 g/km, provisional data)1 meets the highest of demands: in addition to the usual, extensive programme of crash tests, Mercedes-Benz applies further, particularly stringent safety standards to the battery and all component parts carrying electrical current.

Daimler applies extremely high safety standards to all its models. This is true for both vehicles with a conventional internal combustion engine and those with an alternative drive. This means that, in many cases, internal Mercedes‑Benz safety standards exceed legal requirements. Especially the crash-related requirements are aligned to the so-called Real Life Safety philosophy. These take findings from in-house accident research into account in the development specifications, e.g. the roof drop test. Alongside verification of crash behaviour, all Mercedes-Benz vehicles undergo additional component tests at system level.

The vehicle structure of the EQC allows for the special requirements of the electrical components and battery and is configured to achieve the hallmark high safety level. For example, a new subframe surrounds the drive components located in the front section, and this unit is supported by the usual mounting points. As the battery is housed in the vehicle floor, the EQC also has a low centre of gravity. This reduces the risk of a rollover.

Crash gaps are integrated between the wings and the doors, and like the robust door handles they make it easier to open the doors after a frontal collision.

[1] Figures for power consumption and CO2 emissions are provisional and were determined by the German Technical Service corporation. The range figures are also provisional. EC type approval and conformity certification with official figures are not yet available. There may be differences between the stated figures and the official figures.

The high-voltage system: cut-off facilities in the event of a crash

The extensive experience of Mercedes-Benz with high-voltage drive systems has led to a multi-stage safety concept that deploys in the event of an accident.

Firstly, thanks to the specific design features of the EQC, the likelihood of an external short circuit caused by an accident is considerably reduced. The battery is surrounded by a robust frame with an integral crash structure. Deformation elements are installed between the frame and the battery, and these are able to absorb additional forces in the event of a severe side impact. A battery protection shield in the front area of the battery is able to prevent the energy storage unit from being pierced by foreign objects.

The high-voltage system can also be shut down automatically in a crash, depending on its severity. A distinction is made between a reversible and an irreversible cut-off. In the case of a reversible cut-off, which occurs in less severe accidents, it is possible to switch the high-voltage system back on if a prior insulation measurement detects no faults. This means that vehicles still capable of being driven can continue their journey. Only in the case of very severe accidents, where the vehicle is anyway usually incapable of being driven, is the high-voltage system shut down irreversibly and unable to be activated without a repair. When shutting down, there is a provision to ensure that within a few seconds there is no residual voltage in the high-voltage system outside the battery that could cause injury.

There are also shutdown points where emergency teams can deactivate the high-voltage system manually. The cut-off switch is located in the engine compartment. In addition there is an alternative shutdown point in the form of a marked cable loop as a cutting point in the fuse box on the driver's side of the cockpit. This is intended for use by the emergency services if they are unable to reach the shutdown switch in the motor compartment.

Another feature of the comprehensive high-voltage safety concept is that the charging process is automatically stopped if an impact is detected when stationary at a quick-charging station (DC charging). During a charging process, the vehicle's onboard electrical system and therefore the airbag control unit is usually switched off. So that the charging process is nonetheless ended during a possible impact when quick-charging the vehicle at a DC station, an additional impact sensor system is integrated into the DC box. If it detects a collision with the vehicle, the charging process is automatically stopped.

The battery: multi-stage protection concept for normal operation

The battery itself also features its own multi-stage safety system for day-to-day operation. This includes e.g. monitoring the temperature, voltage and insulation. In normal operation, if a fault is detected here, it can lead to the battery being shut down. A continuously self-monitoring safety system prevents overheating and overloading in different operating states.

Restraint systems: Belts and airbags

In addition to the structural safety and the battery protection concept, the model's specially adapted restraint systems are particularly important for the occupants in the event of an accident. Three-point seat belts with pyrotechnical belt tensioners and belt force limiters are installed for the driver, front passenger and passengers on the outer rear seats. The centre seat of the second row is equipped with a standard three-point belt system. A rear seat belt status display informs the driver whether the passengers in the rear have fastened their seat belts. The seat belt reminder prompts front seat occupants to fasten their seat belts.

i-Size (Europe) and ISOFIX (remaining countries) child seat anchorage points on the outer rear seats ensure safe attachment of appropriate child seats with additional anchorage points at the top of the rear seat backrest (so-called top-tether anchoring). If the front passenger seat is unoccupied or a rear-facing child seat is detected, the “automatic front passenger airbag deactivation” automatically disables the front passenger airbag. This prevents infants from being injured by the deploying front passenger airbag. The reliable recognition function uses a pressure sensor.

In addition, a host of airbags provides occupant protection in an accident. These include:

  • A windowbag in the roof area between the A, B and C-pillars for the head area of the driver, front passenger and passengers on the outer rear seats. These airbags can be deployed on a situational basis, e.g. during a severe lateral impact, when a rollover is detected or in various frontal collisions with strong lateral acceleration components.
  • Combined thorax/pelvis sidebags for the driver and front passenger, which are able to provide additional protection in the event of a side impact. Side impact airbags for the outer rear seats are available as an option.
  • Airbags for the driver and front passenger for a frontal collision, with two-stage staggered deployment on the front passenger side, depending on the detected severity of the frontal collision.
  • Knee airbag for the driver to protect the knees in a severe frontal collision and stabilise the upper body, which positively influences occupant movement.

Numerous measures help to ensure that when Mercedes-Benz vehicles suffer an accident, consequential damage is reduced and rescue of the occupants is assisted. As soon as a protective system (e.g. belt tensioner and airbag) is triggered, an emergency call or a service call is made, or a breakdown is detected, the following measures can be initiated depending on the accident type and severity:

  • Automatic activation of Mercedes-Benz emergency call to notify emergency services of the location and emergency situation and initiate rescue. Data transfer is via a communication module with its own SIM card.
  • Shutdown of the high-voltage system
  • Activation of the hazard warning system to secure the scene of the accident and protect occupants from a follow-on accident.
  • Activation of the interior lighting to help occupants and rescue services find their bearings.
  • Lowering of the front side windows in the event of airbag deployment – serves to ventilate the interior and helps occupants to find their bearings.
  • Opening of the central locking system to facilitate access to the interior for helpers.
  • Raising of the electrically adjustable steering column; facilitates exiting and access to the driver.
  • Sending a recognised breakdown or accident situation to the Car-to-X communication and to the Mercedes-Benz Service Centre (Mercedes me or Service Call) to give a warning of an accident or broken-down vehicle, and to offer the driver automatic contact with the Mercedes‑Benz Service Centre.

Digital support for emergency services: QR code and Rescue Assist App

With a small but effective innovation, Mercedes-Benz has also found a way to give rescue services the best possible support and a clear overview of the vehicle's safety-related features.

The digital Mercedes-Benz rescue helpers interact perfectly: The Rescue Sticker provides a direct link to the vehicle’s rescue data sheet. Corresponding stickers are affixed to the charging flap and to the opposite B-pillar of the vehicle for this purpose. In the aftermath of an accident, rescue services can scan the QR code with a smartphone or tablet PC for fast and reliable access to the rescue data sheet for the specific vehicle concerned, thus facilitating rescue operations.

Alongside the rescue data sheets, the Rescue Assist App for smartphones and tablets also has three-dimensional views of the vehicle – now also offline in case there is no mobile network available at the accident scene.

To ensure practicality, the Mercedes-Benz safety team develops its rescue information and processes together with the fire and rescue services. Furthermore, Mercedes-Benz regularly presents its findings in presentations and training events for fire services, the police and specialist congresses.