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The new EQS: the traction battery[1]

Apr 15, 2021

Modular, efficient and innovative: The lithium-ion battery system of the EQS can be flexibly equipped with pouch or hardcase cells. This scalability enables the realisation of different range and performance variants. Depending on the variant, sufficient energy can be stored for ranges of up to 770 kilometres according to WLTP. The innovative battery management software, developed in-house, allows updates over the air (OTA). The energy management of the EQS is therefore kept up to date throughout the life cycle.

Battery development is a decisive factor in Mercedes-Benz's electrification strategy. After all, the battery is the heart of an electric car and makes a decisive contribution to, among other things, the range and thus the driving characteristics of the electric vehicle. The EQS marks the launch of a new generation of batteries with significantly higher energy density. The largest battery has a usable energy content of 107.8 kWh (according to WLTP). That is around 26 percent more than the EQC (EQC 400 4MATIC: combined electrical consumption: 21.5-20.1 kWh/100 km; CO2 emissions: 0 g/km)[2]. The new batteries set standards in terms of performance, efficiency and charging capacity.

They also meet the high Mercedes requirements in terms of safety, durability and sustainability. Mercedes-Benz issues a battery certificate for its high-voltage batteries and thus a performance promise to customers: A term of 10 years or 250,000 kilometres with a remaining capacity of 70 percent.

Comprehensive battery expertise
The highly efficient batteries were developed entirely in-house by the team of experts at the Mercedes-Benz Battery Centre of Competence. The software for the intelligent management system was also developed and programmed in-house. The batteries are produced in the Hedelfingen plant section at the Stuttgart-Untertürkheim site.

The scalability of the battery system enables the realisation of different range and performance variants. Different battery sizes are available: Depending on the output and drive system layout (rear-wheel drive or 4MATIC), a lithium-ion battery with either 10 or 12 cell modules is installed, which are realised with different cell types in the form of pouch and hardcase cells. The usable energy content is 90 or 107.8 kWh.

For both battery variants, a major step has been achieved in terms of the sustainability of the cell chemistry: The optimised active material consists of nickel, cobalt and manganese in a ratio of 8:1:1. This reduces the cobalt content to less than ten percent. The continuous optimisation of the recyclability is part of Mercedes-Benz's holistic battery strategy (for details, see separate chapter on sustainability). The aim is to be able to dispense entirely with materials such as cobalt through the use of innovative post-lithium-ion technologies. 

Intelligent operating strategy for maximum range
The battery is integrated into the intelligent thermal management of the EQS. If the intelligent navigation with Electric Intelligence is activated, the battery is preheated or cooled as needed while driving to reach the optimal temperature for efficient charging at the charging point. The desired temperature range of the battery is achieved with the aid of the cooling circuit and a PTC (Positive Temperature Coefficient) booster heater integrated into it.  

Complex protection concept for safety
In principle, Mercedes-Benz AG applies very high safety standards to all its models. 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. In the process, findings from internal accident research are incorporated into the development specifications. Alongside verification of crash behaviour, all Mercedes-Benz vehicles undergo additional component tests at system level.

The battery sits in a crash-protected area in the underbody, embedded in the body shell structure including an extruded aluminium profile on the side. In extrusion, a heated block of metal is forced through dies and transformed into a continuous profile, which is then cut to fit. In this way, highly complex profiles can be produced that are precisely tailored to the requirements. The housing with energy absorbing structures at the front and side as well as a rigid, double-walled base plate provide additional protection for the modules. The test criteria include, among other things, the battery behaviour under shock load and in the event of foreign object penetration. Overheating and overcharging were also simulated and tested. In addition, there is a separate, multi-level safety system for everyday operation. This includes, for example, temperature, voltage or insulation monitoring as a continuously monitoring safety system. If an error occurs, the battery is switched off.

Production: Battery systems from Hedelfingen
The batteries for the Mercedes-EQ electric vehicles are supplied by the global battery production network with factories on three continents. Local battery production is a key success factor for Mercedes-Benz's electric initiative.

The battery systems for the EQS are produced in the Hedelfingen plant section at the Stuttgart-Untertürkheim site. Absolute precision is required in their manufacture. The battery systems consist of a large number of components, including up to 12 cell modules and the so-called EE compartment for intelligent integration of the power electronics. It is assembled at the Mercedes-Benz location in Berlin.

The Mercedes-Benz Hedelfingen plant will have carbon-neutral production from 2022. The Hedelfingen plant is a prime example of the transformation of production sites as part of the Mercedes-Benz Electric First strategy. The efficient and seamless integration of battery production alongside existing transmission production transforms Hedelfingen's traditional role as a site for conventional powertrain components into an important part of the company's global battery production network.

The suppliers of the battery cells have undertaken to use electricity from renewable energy sources such as hydropower, wind and solar energy in the production of the battery cells. The supplier network accounts for a substantial share of value creation, and is therefore of decisive importance for the decarbonisation targets. Already, around half of all suppliers have signed a corresponding declaration of intent. Because of the higher energy requirements in the production of all-electric vehicles, the supplier network is a crucial component in achieving Mercedes-Benz's climate targets.

[1] All technical information (concerning operating range, output, torque, recuperation and performance) in this publication is provisional, and was obtained internally in accordance with the applicable certification method. Confirmed TÜV figures, EC type approval and conformity certification with official figures are not yet available. Differences between the stated figures and the official figures are possible

[2] The electrical consumption and the range have been determined on the basis of Commission Regulation (EC) 692/2008.