|S 500 PLUG-IN HYBRID. Click to enlarge.|
Mercedes-Benz unveiled the third hybrid model of the new S-Class, the S 500 PLUG-IN HYBRID, prior to its introduction in a few weeks at the Frankfurt Motor Show. (Earlier post.) Market launch for the plug-in will be next year.
The S 500 PLUG-IN combines an 80 kW, 340 N·m electric motor, externally rechargeable battery, and a new 245 kW, 480 N·m 3.0-liter turbocharged V6 engine. Fuel consumption is 3 l/100 km (78 mpgUS), with about 30 km (18.6 miles) of all-electric range possible. CO2 emissions are 69 g/km. Top speed is 250 km/h (155 mph), with 0-100 km/h acceleration in 5.5 sec.
The S 400 HYBRID was the first to feature a standard-specification hybrid drive system with lithium-ion battery in 2009. With the new S-Class, Mercedes-Benz expands the hybrid line-up in this model series to three models: the S 400 HYBRID, S 300 BlueTEC HYBRID and S 500 PLUG-IN HYBRID. All second-generation hybrid drive systems share the same integration into the powertrain. The combustion engine can be completely decoupled from the electric motor. Further features are the second-generation recuperative braking system and the anticipatory Intelligent HYBRID energy management system.
While the batteries of the S 400 HYBRID and S 300 BlueTEC HYBRID as autonomous hybrids are charged during braking or coasting or by the combustion engine, the new high-voltage lithium-ion battery of the S 500 PLUG-IN HYBRID has ten times the energy content and offers the option of being recharged from an external source with a charging socket located on the right side of the rear bumper.
Four hybrid operating modes can be selected at the push of a button:
- E-MODE: electric power only
- E-SAVE: fully charged battery is reserved to be able to drive on electric power alone later
- CHARGE: battery is charged while driving
A haptic accelerator pedal enables superior vehicle control; a point of resistance on the accelerator pedal provides feedback about the activation of the combustion engine and helps in metering the power output.
The second-generation S-Class hybrids feature an anticipatory energy management system and thereby improve energy efficiency. The operating strategy of the hybrid drive system not only accounts for the current driving condition and driver input, but also adjusts to the likely route (inclines, downhill stretches, bends or speed limits) for the next eight kilometers.
Intelligent HYBRID uses the navigation data from COMAND Online to manage the charging and discharging of the high-voltage battery. The goal is, for example, to use the energy content of the battery for propulsion ahead of a downhill stretch in order to recharge it while going downhill using recuperation.
The largest potential for lowering the energy consumption of hybrid drive systems lies in maximizing energy recovery during coasting and braking. Upon depressing the brake pedal the deceleration is initially effected by the electric motor and not by the disc brakes. The new S-Class is the first to use a recuperative braking system (RBS) of the second generation. It ensures an unnoticeable overlapping of the conventional mechanical brakes and the electric braking performance of the electric motor in alternator mode.
The driver’s desired braking power is recorded by a pedal-travel sensor. The deceleration is dependent on the driving condition and is split into a recuperative brake-force portion and a portion to be supplied by the wheel brakes. The brake pressure on the rear axle is controlled by the RBS dependent on the current recuperation potential of the powertrain.
In addition, the combustion engine is switched off any time the vehicle is coasting and its drag torque when rolling is used by the electric motor as recuperation torque. However, without depressing the brake pedal no additional deceleration torque is provided for charging the battery and the vehicle can “sail”. The combustion engine is to be used for charging the battery as little as possible and only at suitable and most efficient operating points.