On the road to purely electric mobility, plug-in hybrids represent what is perhaps the key bridging technology. With its EQ Power models, Mercedes-Benz is presenting an efficient drivetrain package which is already in its third generation, marking a further step towards CO2-neutral mobility. Mercedes-Benz customers will be able to experience the advantages of the technology by the end of 2020 in more than 20 different model variants.
In the plug-in hybrid, the positive characteristics of the electric drive and combustion engine complement one another, virtually completely offsetting the restrictions of the respective systems. The main advantage of the hybrid technology is the possibility of locally emission-free driving when it counts, in combination with the autonomy familiar from the conventional car. Range anxiety is not something plug-in hybrid drivers have to deal with. Relatively large lithium-ion batteries ensure purely electric operating ranges which are more than sufficient for most daily journeys. Mercedes-Benz will roll out this pioneering technology across the entire range – from the A- to the S-Class, from the GLA to the GLE the combustion engines are being given electric supporters. They draw their energy from batteries which can be charged conveniently and quickly at home, at the charging station at work or from the public network.
Mercedes-Benz Research has used methods such as the EQ Ready App to determine just how big the distances are which are covered on average by e-mobilists. The analysis shows that a purely electric range of 50 kilometres is sufficient for 90 percent of all journeys. The proportion of longer trips is vanishingly small – more than 90 percent of all journeys are shorter than 100 kilometres and most of the journeys are shorter than 400 kilometres. The third-generation plug-in hybrids are an ideal fit for these results.
Plug-in hybrid technology for compact models
For models with a transversely installed engine and the 8G-DCT dual-clutch transmission, a compact hybrid traction head was developed whose electric machine works as a permanently excited synchronous machine with an internal rotor. Its stator is an integral component of the traction head housing, the rotor of the electric motor comprises the low-loss separator clutch running in the oil bath. On-demand stator and rotor cooling makes it possible to call on both the peak and continuous performance of the electric machine without any compromise. The structure of the hybrid components enables Mercedes-Benz to do without a classic 12 V starter, as only the electric machine is used for starting and boosting the combustion engine. As well as efficiency, the compact drive unit brings a generous portion of driving pleasure and suitability for everyday use. The technical highlights of the compact-class hybrids alone speak for themselves here:
- Electric range up to 77 km (NEDC)
- Electric output 75 kW
- System output 160 kW
- System torque 450 Nm
- Top speed 140 km/h (electric)/235 km/h (total; A-Class Compact Saloon)
- Acceleration 0-100 km/h in 6.6 seconds (A-Class Compact Saloon)
- Virtually no restrictions on luggage compartment
As the EQ Power alliance the electric machine and the 1.33-litre four-cylinder engine generate 160 kW (218 hp) and develop an overall maximum torque of 450 Nm. The hallmark characteristic of the electric machine, namely full torque from a standstill, ensures that the compact plug-in hybrids react immediately to the accelerator pedal. The performance values are correspondingly impressive: for example, the A 250 e (combined fuel consumption 1.5-1.4 l/100 km, combined CO2 emissions 34-33 g/km, combined electrical consumption 15.0-14.8 kWh/100 km)¹ completes the classic sprint from 0 to 100 km/h in just 6.6 seconds. Not until a top speed of 235 km/h does wind resistance limit power delivery.
The latest battery generation with a high energy density
A lithium-ion battery with an overall capacity of approx. 15.6 kWh serves as an energy storage unit for the electrical system. It can be charged with alternating or direct current. The vehicle's connection for this, practically the electric fuel cap, is located in the rear area of the right-hand side wall. The compact plug-in hybrids can be charged via this at a 7.4 kW wallbox with alternating current (AC) within 1 h 45 min from 10-100 percent SoC. With the faster direct current (DC) the charging time reduces to just 25 minutes from 10-80 percent SoC. The water-cooled batteries weighing approximately 150 kilograms are supplied by the fully owned Daimler subsidiary Deutsche ACCUMOTIVE. For the third-generation Mercedes-Benz plug-in hybrids known as EQ Power the company uses batteries with advanced cellular chemistry. The leap from lithium-iron-phosphate (LiFePo) to lithium-nickel-manganese-cobalt (Li-NMC) made it possible for the cell capacity to be increased from 22 to 37 Ah. As a result it was possible to give the battery packs a more compact design, with advantages for the boot capacity and space available for the occupants.
Plug-in hybrid technology for longitudinal installation
Since the launch of hybrid technology at Mercedes-Benz in the year 2009 in the S 400 Hybrid, the drivetrain has been systematically advanced for longitudinal installation. For the latest generation named EQ Power the developers above all redesigned the electric machine in the 9G-TRONIC plug-in hybrid transmission. It works as a permanently excited synchronous machine with an internal rotor. Higher-performance power electronics enable it to achieve higher output and torque density. The torque converter with integral lockup clutch represents a further impressive innovative leap. In spite of the further increased output, the design of the electric machine remains extremely compact. All in all the transmission is only 108 mm longer than the basic 9G-TRONIC transmission. The most powerful version of it with a transferable torque of up to 700 Nm is employed for hybrid use, so that the combined power of the combustion engine and electric motor can be used permanently.
This drive system celebrated its premiere in the Mercedes GLE 350 de 4MATIC (weighted fuel consumption 1.1 l/100 km, weighted CO2 emissions 29 g/km, weighted electrical consumption 25.4 kWh/100 km). Its considerably longer electric range compared with the other plug-in hybrids guarantees an even more rewarding, locally emission-free e-driving experience. Key data:
- Electric range of up to 106 km (NEDC)
- Electric output 100 kW
- System output 235 kW/320 hp
- System torque 700 Nm
- Top speed up to 160 km/h (electric)/210 km/h (overall)
- Acceleration from 0-100 km/h in 6.8 seconds
With its battery capacity of 31.2 kWh the GLE 350 de achieves an electric range of over 100 kilometres (according to NEDC) with the appropriate driving style. Should this long range ever be insufficient, the GLE 350 de also allows fast recharging via its COMBO vehicle socket using alternating current/AC and direct current /DC charging. It is on the left-hand rear side wall. At DC rapid-charging stations, electric charging is possible in approx. 20 minutes (10-80 percent state of charge (SoC)) or in approx. 30 minutes (10-100 percent SoC).
Mercedes me Charge makes charging easier
As an option, with the Mercedes me Charge service, Mercedes-Benz plug-in hybrid drivers have access
to one of the world's most extensive charging networks. Via the Mercedes me app or the MBUX (Mercedes-Benz User Experience) infotainment system, extensive information can be called up on charging stations or navigation to a charging point started. The MBUX system's natural speech recognition enables a search for charging stations in the vicinity or along the chosen route. This makes searching, charging and paying as convenient as never before.
Intelligent operating strategy supports the driver
So that the distances between the individual charging processes are as long and the charging time as short as possible, the vehicle electronics of the EQ Power models support the driver in efficient driving with an intelligent and route-based operating strategy. It recommends the electric driving mode where it makes best sense in each case, taking into account, for example, navigation data, topography, speed limits and the traffic conditions for the entire planned route. What is known as the ECO Assist supports the driver as a type of coach and helps save electricity and fuel. If the ECO Assist's coach is systematically followed, consumption can be cut by up to five percent compared with a normal driving profile.
Plug-in hybrid with CO2 saving potential
The Daimler environmental experts include emissions and consumption of resources across the entire life cycle when considering the environmental compatibility of a vehicle – from raw material extraction through production and use to recovery. Despite the higher energy use in production of a hybrid the life cycle assessment is positive. The fact is that a third-generation Mercedes-Benz plug-in hybrid produces a CO2 output approximately 20 percent higher than a comparable model with conventional drive, and this is mainly down to the high-voltage battery.
Systematic use of the plug-in function, i.e. regular charging of the battery via the network, combined with the higher efficiency in operating status itself, cuts the CO2 output by 40 percent, even with the energy mix currently available in Germany. If the starter battery is charged exclusively with green power, the CO2 saving of the EQ Power models from Mercedes-Benz even rises to 70 percent. The large batteries from the current plug-in hybrid generation, in conjunction with the powerful electric machines, do facilitate an efficient operating status, even if the purely electric range itself is actually exhausted. Strong recuperation ability and the intelligent operating strategy ensure that the battery never actually discharges completely. This means that the electric machine can support the combustion engine repeatedly even on long journeys, and even brief moments in overrun mode form the basis for this. This means that the combustion engine runs in the optimum and particularly efficient map much more often than is possible with conventional drives.
In spite of the larger “CO2 backpack” due to the higher energy use in production, the plug-in hybrid saves a large amount of CO2 across the entire life cycle and in the best-case scenario it achieves only about 45 percent of the total emissions of a comparably powerful, conventionally driven model. Thus, in this case more CO2 emissions during the manufacturing phase are an investment that – when using the electric potential through regular charging – can more than pay off over the entire life cycle.
¹ The stated figures are the measured "NEDC CO2 figures" in accordance with Art. 2 No. 1 Implementing Regulation (EU) 2017/1153. The fuel consumption figures were calculated based on these figures. The range and the power consumption have been determined on the basis of Regulation (EC) No. 692/2008. A different value is applied in accordance with EmoG. A higher figure may apply as the basis for calculating the motor vehicle tax. Further information on the official fuel consumption and the official specific CO₂ emissions of new passenger cars can be found in the publication "Leitfaden über den Kraftstoffverbrauch, die CO₂-Emissionen und den Stromverbrauch neuer Personenkraftwagen" [Guide to fuel consumption, CO₂ emissions and electrical consumption of new passenger cars] which is available free of charge at all sales outlets and from Deutsche Automobil Treuhand GmbH at www.dat.de.