The Mercedes-Benz C350 Plug-In Hybrid premieres in the US this week and marks the second road-ready step in the German brand’s significant embrace of the bridging technology, though its Australian future remains unclear.
As part of a trickle-down ethos, the C350 PHEV follows in the wheel tracks of the flagship S500 plug-in model that we drove in September last year. Up to 2017, the company is shooting to have launched 10 plug-in models across its core passenger and SUV range.
Benz in fact claims to have a strong history in electrification. Think of the (then-radical) 1982 concept hybrid with a two-cylinder horizontally opposed engine that charged the batteries and its sizeable early investments and co-op deals with Silicon Valley icon Tesla.
Unlike the existing Mercedes-Benz C300 BlueTec diesel hybrid sold in Australia, the C350 PHEV uses a petrol engine in conjunction (the level of conjunction is decided by advanced engine management software) with a small electric motor and battery pack that can be charged externally through a socket near the tail-light via a wallbox or fast charger.
Think of the car as a petrol variant with a small supplementary electric source to cut fuel use, rather than an electric car with a petrol back-up, and you’re about on the money.
Also unlike the conventional, non plug-in C300 diesel hybrid, the C350 PHEV comes in both sedan and Estate wagon body styles, the latter of which somewhat alleviates the packaging constraints still inherent to Mercedes’ PHEV system.
Unlike the S500 that uses a V6 engine as one half of its powertrain, the C350’s petrol unit is the brand’s familiar 155kW/350Nm 2.0-litre turbocharged four. This tag-teams with a 60kW/340Nm electric motor. Combined, the pair makes up to 205kW/600Nm in total system output.
According to Mercedes-Benz, pure electric (zero emissions) range is 31km, which falls short of the Holden Volt (87km) and Mitsubishi Outlander PHEV (52km). The electric motor works solo under low duress situations such as inner-urban driving at low speeds, or acts as a 60kW booster to the IC engine during heavy acceleration.
A new ‘haptic accelerator’ pedal provides assistance here. In full electric mode, the throttle pedal provides a point of resistance at the limit of the motor’s power. Press on beyond this warning and the petrol engine jumps in to assist.
This small motor is incorporated within the seven-speed automatic transmission. A separate clutch operates between the motor and the petrol engine. In pure EV mode, the subsidiary clutch decouples the petrol engine.
The electrical storage unit is a lithium-ion battery with a 6.2kWh capacity. It’s a water-cooled unit that weighs about 100kg and is mounted in sheet metal under the rear axle. Both braking — the motor partially brakes the car in the guise of an alternator — and coasting regenerate power that is stored here.
A 230-volt, 16-amp, single-phase public charger can top the cells up in about one hour and 45 minutes. A 13A socket will charge the cells in about two hours. The car’s Charge mode also allows the battery to be gradually recharged while driving using the combustion engine as generator, though the motor is disengaged during the process.
The positioning of the batteries reduces storage space to a significant degree, given the company claims boot space in the sedan of 335L (regular IC models are 480L) and up to 1370L in the Estate with the seats folded (IC versions have 1510).
Naturally, as with any PHEV, consumption depends entirely on your driving style and the distance covered. Official consumption figures peg the car at 2.1L/100km on the combined cycle for both body styles, equating to emissions of 48g/km. As always, longer trips can use more fuel given the cells deplete quickly, though not always thanks to some clever driving modes as discussed a little lower in the story.
One benefit of all that instantaneous electric torque is a swift 0-100km/h sprint time in the sedan of 5.9 seconds (6.2sec in Estate).
The C350 PHEV has five driving modes — Individual, Sport Plus, Sport, Comfort and Eco — that recalibrate the drive system, chassis/suspension, steering, Eco Assist and climate control depending on the style you wish to drive in.
A switch is also present that influences the regulation between electric mode and the use of the IC engine in both Eco and Comfort settings. One example is E-save, which allows you to essentially disengage the electric system to save the juice for later, such as when you arrive in a city at the end of your journey.
The car also has a route-based operating system that uses navigation data to charge and discharge the battery at the most appropriate moments over the route. So for instance, the car will hold back as much charge as it can if it sees you’re doing lots of urban driving later.
Less exotic standard equipment includes Airmatic adjustable air suspension, and pre-entry climate control that allows you to set the temperature before entry (via a timer or online) as in most regular electric cars. This website also has a profile section that allows you to monitor charging remotely.
Otherwise, the C350 PHEV is just like a regular C-Class, inside the cabin and from the outside (aside from the badge on the back), which is just the means by which Mercedes-Benz wants to normalise such vehicles.
So what of the C350 PHEV's Australian launch? Well, given this country's slow uptake of alternative energy vehicles, Mercedes-Benz's local arm is sitting on the fence for now, saying only that the car is "under evaluation", unlike the already confirmed S-Class PHEV that arrives late in the year.
Mercedes-Benz Australia public relations, product and corporate communications general manager David McCarthy says the C350 plug-in would need to be priced around $90,000 plus on-road costs to be viable in Australia. The regular C300 hybrid costs $74,900.