More on the Mercedes-Benz 2014 B-Class alternative drive systems: electric and natural gas

21 October 2014

B-Class Electric Drive (right) and B-Class Natural Gas Drive (left). Click to enlarge.

Mercedes-Benz earlier gave the already successful B-Class a thorough facelift, giving particular attention to an upgrade of the interior. (Earlier post.) The revamped B-Class offers a choice of five diesel models with fuel ranging from 3.6 to 5.0 l/100 km (65.3 to 47 mpg US) and four gasoline engines at between 5.4 and 6.6 l/100 km (43.6 and 35.6 mpg US) as well as the B-Class Electric Drive (earlier post) and the B 200 Natural Gas Drive.

Both alternative drive models feature the modular “ENERGY SPACE” bodyshell concept: the underbody houses either the lithium-ion battery (B-Class Electric Drive) or one large and two smaller natural gas tanks and a 14‑liter gasoline tank (B 200 Natural Gas Drive). The B-Class Electric Drive and the B-Class Natural Gas Drive also differ in design from the gasoline and diesel models—particularly in the shaping of the front and rear aprons and the side skirts.

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As part of the facelift, Mercedes-Benz also revised the model range and aligned it logically with the other compact models. The two new design and equipment lines for the models with alternative drive systems have been given the names Style and Urban. A further line, Electric Art, is available as an option for the B-Class Electric Drive.

B-Class Electric Drive

Mercedes-Benz says that the B-Class Electric Drive offers a fully electric range of around 200 kilometers (124 miles). Full climate control for the interior as standard and some optional extras, such as the recuperative braking system with radar support or the RANGE PLUS battery-based range extender, add to the ride comfort and practicality.

B-Class Electric Drive. Click to enlarge.
 
Electric powertrain, B-Class Electric Drive. Click to enlarge.

The electric B-Class was developed by Mercedes-Benz in collaboration with Tesla Motors; the car uses a Tesla drive system. (The battery for the predecessor model of the smart fortwo electric drive, for instance, also comes from Tesla.)

The electric motor generating more than 132 kW with maximum torque of more than 340 N·m (251 lb-ft)—approximately equivalent to the torque from a modern, naturally aspirated three-liter gasoline engine. The B-class takes 7.9 seconds to accelerate from 0 to 100 km/h.

Electric motor and transmission. Click to enlarge.

According to whether the driver wishes to drive economically or perhaps with more emphasis on comfort or sportiness, there is a choice of three driving programs:

• E+ (Economy Plus): This driving mode is configured for a defensive driving style and lends itself to driving at a constant, steady speed. The output here is reduced to around 65 kW, whereby the top speed falls to around 110 km/h (68 mph) on the flat. With kickdown, however, an output of 132 kW and a top speed of up to 160 km/h (99 mph) remain available.

• E (Economy): The philosophy here is a comfortable driving experience. The output is restricted to 98 kW, although kickdown will summon up as much as 132 kW.

• S (Sport): This mode delivers maximum output for maximum acceleration; the engine can call upon the full 132 kW.

In the interests of optimizing the range, the top speed is electronically limited to 160 km/h.

The instrumentation of the B-Class Electric Drive is rounded off by functions that are specific to electric vehicles. One of the features is the power display in the right-hand circular instrument. When full power is demanded by the driver, the instrument pointer moves in a clockwise direction from the green zone towards the red zone, dropping back below the zero line when the vehicle is feeding energy into the battery through the recuperation feature.

B-Class Electric Drive interior. Click to enlarge.

As protection for pedestrians and cyclists, a specific Mercedes-Benz sound is generated (optional extra) at speeds of up to 30 km/h (18.6 mph). Once over 30 km/h this is no longer necessary, as wind and tire noise then begin to dominate.

On the road, the electric drive makes its own contribution to a favorable energy balance by recovering energy under overrun conditions as well as by converting the kinetic energy produced during braking into electric power and feeding it to the battery. This process is controlled through the energy management system.

The level of recuperation and thus of drag deceleration can be influenced by the driver via the brake pedal (approx. 10% of pedal travel). The potential recuperation performance depends, among other factors, on the state of charge and the temperature of the high-voltage battery.

Particularly effective energy recovery and thus an extension of the vehicle’s range are made possible with the optional extra of a radar-supported, recuperative braking system. The system also supports the driver in controlling proximity and speed.

The system uses the data from the radar sensors of COLLISION PREVENTION ASSIST PLUS to increase or reduce to zero, as appropriate, the level of recuperation and thus of deceleration.

If the system detects a slow-moving or slowing vehicle ahead, it triggers an increase in recuperation torque and thus a reduction in speed. If, on the other hand, any vehicle it detects is far in the distance or accelerating away, the vehicle will switch into energy-saving “sailing” mode, without recuperation.

This is particularly useful in town or on fast roads with a slight downhill incline. When driving downhill in “sailing” mode or on a steep slope, an increase in recuperation will restrict acceleration. The effect here is comparable to changing down a gear.

In conjunction with COMAND, the regulation is extended to take account of information supplied by the traffic sign recognition system as well as of speed limits stored in the navigation system.

With this optional equipment item, the driver is also able to use the steering-wheel gearshift paddles to switch between four stages of recuperation — from sailing through to a high level of recuperation with a sporty accelerator pedal curve. The following four recuperation stages are available:

• D+: sailing mode, no recuperation
• D: moderate recuperation
• D-: high recuperation
• D^Auto: recuperation according to the traffic situation

The power supply to the electric drive comes from a high-performance lithium-ion battery (capacity 28 kWh), which is fitted in the ENERGY SPACE. The charger for the battery is located in the engine compartment. A full recharge of the battery is possible in just three hours or so (400 V, 3-phase, 16 A). At a normal domestic socket (230 V, single-phase) it is normally possible to recharge the B-Class Electric Drive overnight. With 16 A circuit protection, this only takes about 9.1 hours.

The control light on the vehicle socket will remain illuminated throughout the charging process. The vehicle cannot be started or moved during this phase. Information about the current state of charge is shown in the multifunction display. Following completion of the charging process, the charging cable may be removed.

RANGE PLUS. The optional RANGE PLUS extends the range of the vehicle by as much as 30 km (18.6 miles). Activating the RANGE PLUS button in the upper control panel extends the chargeable capacity of the battery the next time it is charged—i.e. more capacity is released. As over-frequent use of this function can reduce the lifespan of the battery more quickly, it should only be used when a long trip is planned or when there is only limited availability of charging points.

Each battery is certified by Mercedes-Benz as a guarantee of performance. This ensures that any technical malfunction within a period of eight years after initial delivery or registration, or up to a mileage of 100,000 kilometers, will be corrected by Mercedes-Benz.

Convenient pre-heating or cooling as standard. The thermal management system of the B-Class Electric Drive encompasses on the one hand the air conditioning for the vehicle interior and on the other hand the cooling of the electric drive. This ensures that all components perform to full efficiency even on long uphill slopes or in high outside temperatures. The high-voltage battery is cooled via a low-temperature circuit. At very high temperatures this can be boosted by the coolant circuit of the air-conditioning system. For low temperatures, a battery heater is available.

For heating and cooling of the interior, the B-Class Electric Drive is equipped as standard with THERMOTRONIC automatic climate control. This uses a high-voltage PTC heater and a high-voltage air conditioning compressor.

Using “Mercedes connect me”, the driver can pre-heat or pre-cool the vehicle — depending on the temperature — in readiness for an individually defined departure time.

Mercedes connect me. Mercedes connect me services are even more extensive for the B-Class Electric Drive: for added convenience, for example, connect.mercedes.me can be used remotely to determine the current state of charge of the lithium-ion battery or the possible range of the vehicle.

ChargePay for Mercedes-Benz app. Mercedes-Benz is now offering “ChargePay for Mercedes-Benz”—an app allowing Mercedes-Benz and smart customers to find available charging stations and manage the whole charging and payment process. Payment is made simply and transparently using PayPal.

ChargePay for Mercedes-Benz does not involve any binding contracts or regular fees. The app can be downloaded free of charge for the iOS and Android operating systems from December 2014.

The app, developed in cooperation with Bosch Software Innovations GmbH, shows the location of available charging stations in the vicinity. Before charging, the app shows the price at the station in question, and customers can conveniently verify their identity using their smartphones. Every charging process is paid for automatically using PayPal.

Instead of entering into contracts with a number of different charging station operators, often involving fixed terms and regular fees, customers using the new app benefit from the convenience of a single solution. The app offers access to almost the entire remote-compatible (i.e. accessible via smartphone) public charging infrastructure in Germany. Other European markets are set to be added one by one. Mercedes-Benz is also planning to make it possible to reserve charging stations as part of the next phase of development.

B 200 Natural Gas Drive

B-Class Natural Gas Drive. Click to enlarge.

The Mercedes B 200 Natural Gas Drive features CO₂ emissions that are more than 16% lower; markedly cleaner exhaust emissions than with gasoline or diesel; and fuel costs which are some 50% below those of a comparable gasoline-powered car. It has been possible to order the facelifted version since 12 September and the car will be making its way to dealers in Europe from 29 November onwards.

When running on natural gas, the fuel consumption of the 115 kW (156 hp) B 200 Natural Gas Drive stands at 4.2 kg/100 km, corresponding to CO₂ emissions of 115 g per kilometre. The emission figures are thus about 16% lower than those of the gasoline-driven B 200 BlueEFFICIENCY, which offers equivalent performance.

The new model is classified as an efficiency class A vehicle and meets the EURO 6 emissions standard.

The B 200 Natural Gas Drive can reach speeds of up to 200 km/h (124 mph), and accelerates from 0 to 100 km/h in 9.1 seconds (with 7G-DCT automatic transmission; with six-speed manual transmission the figure is 9.2 seconds).

The B 200 Natural Gas Drive operates according to the monovalent+ principle. This means that its engine generally runs on gas. For emergencies, however, there is a small 12-liter petrol tank on board. In the event that the gas tank should ever run dry, the vehicle switches automatically, and imperceptibly, to gasoline operation.

As the driver is not able to select gasoline mode himself/herself, the B 200 Natural Gas Drive is taxed more favorably as a natural gas vehicle. The range in natural gas mode is around 500 kilometers (311 miles).

The trip computer menu in the instrument cluster has been extended in the case of the B 200 Natural Gas Drive: the respective operating mode is displayed. In addition, a fill level indicator and remaining range are included for petrol mode. In gas mode, the driver has access to all of the regular trip computer functions.

The vehicles can also be operated using biogas or synthetically produced gas produced using excess energy from solar power plants or wind farms.