On the way to purely electric mobility, plug-in hybrids represent an important bridging technology for many car manufacturers. In its third generation, Mercedes-Benz is presenting an efficient drive package with its EQ Power models, thus taking a further step towards CO2-neutral mobility. Mercedes-Benz customers will be able to experience the advantages of this technology in more than 20 different model variants by the end of 2020.
In the plug-in hybrid, the positive characteristics of the electric drive and the combustion engine complement each other and almost completely balance out the limitations of the respective systems, according to Daimler in a recent announcement. The main advantage of hybrid technology is the possibility of locally emission-free driving when it matters, combined with the autonomy familiar from conventional cars. Plug-in hybrid drivers are not aware of the fear of range. At the same time, relatively large lithium-ion batteries ensure purely electrical operating radii that are more than sufficient for a large part of daily driving.
Mercedes-Benz will roll out this technology across the entire range - from the A-Class to the S-Class, from the GLA to the GLE, the combustion engines will have electric assistants. These draw their energy from rechargeable batteries, which can be conveniently and quickly charged at home, at the charging station at the workplace or on the public grid.
Mercedes-Benz Research has used the EQ Ready App to determine the average distances covered by e-mobilists. The analysis shows that a purely electric range of 50 kilometres is sufficient for 90 per cent of all trips. The proportion of longer trips is negligible - more than 90 per cent of all trips are shorter than 100 kilometres and a large proportion of all trips are shorter than 400 kilometres. The third-generation plug-in hybrids are an ideal match for these results.
Plug-in hybrid technology for compact models
A compact hybrid drive was developed for models with the transversely mounted engine and the 8G-DCT dual-clutch transmission. For the first time at Mercedes-Benz, the design of the hybrid components makes it possible to dispense with a classic 12-volt starter, as only the electric motor is used to start and run the combustion engine.
As an EQ Power combination, the electric motor and the 1.33-litre four-cylinder engine produce 160 kW (218 hp) and develop a maximum total torque of 450 Nm. The typical characteristic of the electric machine, full torque from a standstill, allows the compact plug-in hybrids to react particularly spontaneously to the accelerator pedal. The driving performance is correspondingly dynamic: For example, the A 250 e completes the classic sprint from 0 to 100 km/h in just 6.6 seconds. Only at a top speed of 235 km/h do the driving resistances limit the propulsion.
The latest generation of batteries with high energy density
A lithium-ion battery with a total capacity of 15.6 kWh serves the electrical system as energy storage. It can be charged externally with the alternating or direct current on a 7.4 kW wallbox with alternating current (AC) from 10-100 per cent SoC (status of charge) within 1 h 45 min. With faster direct current (DC) charging, the charging time shrinks from 10-80 per cent SoC to only about 25 minutes.
The water-cooled batteries, which weigh around 150 kilograms, are supplied by Deutsche ACCUMOTIVE, a wholly-owned Daimler subsidiary. The company uses the third-generation Mercedes-Benz plug-in hybrid batteries with advanced cell chemistry for EQ Power. The leap from lithium iron phosphate (LiFePo) to lithium nickel manganese cobalt (Li NMC) has made it possible to increase cell capacity from 22 to 37 Ah. Accordingly, the battery packs could be made more compact, with advantages in terms of luggage compartment volume and space for passengers.
Plug-in hybrid technology for longitudinal installation
Since the introduction of hybrid technology at Mercedes-Benz in 2009 in the S 400 Hybrid, the driveline has been consistently further developed for longitudinal installation. For the latest generation, known as EQ Power, the developers have redesigned above all the electric motor in the 9G-TRONIC plug-in hybrid transmission. It operates as a permanently excited synchronous machine with an internal rotor. Higher-performance power electronics help it to achieve a higher power and torque density. Its torque converter with integrated torque converter lock-up clutch represents a further innovative leap forward. Despite the increased power, the design of the electric machine remained compact. Overall, the transmission is only 108 mm longer than the 9G-TRONIC basic transmission. It is the most powerful version with a transmittable torque of up to 700 Nm for hybrid applications in order to be able to use the combined forces of the combustion engine and electric motor on a permanent basis.
This drive system celebrated its premiere in the Mercedes GLE 350 de 4MATIC. Its significantly longer electric range compared to the other plug-in hybrids guarantees an even more pronounced, locally emission-free e-driving experience. With its battery capacity of 31.2 kWh, the GLE 350 de achieves an electric range of more than 100 kilometres (according to NEDC) when driven accordingly. If this long-range is not enough, the GLE 350 de also allows for quick recharging via its COMBO charging port for AC/AC and DC/DC charging. It is located in the left rear side panel. At DC rapid charging stations, recharging is possible in approx. 20 minutes (10-80 per cent SoC/charge level) or in approx. 30 minutes (10-100 per cent SoC).
Mercedes me Charge makes loading easier
As an option, Mercedes-Benz plug-in hybrid drivers can access one of the world's largest retail networks with the Mercedes me Charge service. The Mercedes me an app or the MBUX (Mercedes-Benz User Experience) infotainment system can be used to call up a wealth of information on charging points or to start navigation to a charging point. The natural language comprehension of the MBUX system allows you to search for charging points in the vicinity or along the selected route. This makes finding, charging and paying particularly convenient.
The intelligent operating strategy supports the driver
To ensure that the intervals between charges are as long as possible and the charging time as short as possible, the onboard electronics of the EQ Power models support the driver in driving efficiently with an intelligent and route-based operating strategy. It recommends the electric driving mode for the most sensible route sections, taking into account navigation data, topography, speed regulations and traffic conditions for the entire planned route. The so-called ECO Assistant assists the driver as a kind of coach and helps to save electricity and fuel. If the ECO Assistant coach is followed consistently, consumption can be reduced by up to five per cent compared to a normal driving profile.
Plug-in hybrid with great CO2-saving potential
When considering the environmental compatibility of a vehicle, the environmental experts at Daimler take into account the emissions and resource consumption over the entire life cycle - from the extraction of raw materials to production, use, and recycling. Despite the greater effort involved in manufacturing a hybrid, the environmental balance sheet is positive. The fact is that a third-generation Mercedes-Benz plug-in hybrid produces approximately 20 per cent more CO2 emissions during production than a comparable model with a conventional drive system, and the high-voltage battery is a major contributory factor.
Consistent use of the plug-in function, i.e. regular recharging of the battery on the mains, combined with the higher efficiency in driving operation itself, reduces CO2 emissions by 40 per cent, even with the electricity mix currently available in Germany. If the vehicle battery is charged exclusively with green electricity, the CO2 savings of the EQ Power models from Mercedes-Benz even increase to up to 70 per cent. In fact, the large batteries of the current plug-in hybrid generation, in conjunction with the powerful electric motors, enable particularly efficient driving, even when the purely electric range is actually exhausted.
The recuperation capacity and the intelligent operating strategy ensure that the battery is basically never completely discharged. This means that the electric machine can support the combustion engine again and again, even over long distances. As a result, the combustion engine runs in the optimum and particularly efficient map much more frequently than is possible with conventional drives.
Despite the larger "CO2 rucksack" caused by the more complex production process, the plug-in hybrid saves a large amount of CO2 over its entire life cycle and, in the best case, only achieves around 45 per cent of the total emissions of a comparably powerful, conventionally driven model. In this case, therefore, more CO2 emissions during production are an investment that - if the electrical potential is used by regular charging - can more than pay for itself over the entire life cycle.
Source: Daimler - Press release as of April 15, 2020