Daimler plug-in hybrid for series production?

  • 24-Jun-2008 07:31 EDT
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The Mercedes Sprinter plug-in hybrid has a range of 30 km (19 mi) using electric power on a fully charged battery.

Daimler looks set to introduce a series-production hybrid Mercedes-Benz Sprinter cargo van. The company is about to begin trials of its “second-generation” plug-in parallel hybrid Sprinter in the U.S. with a fleet of 11 vehicles. Two further vehicles will be trialed in Germany. These models will be gasoline hybrids following earlier European trials of diesel-hybrid models.

The drivetrain makes use of a drive motor/alternator sandwiched between a 258-hp (190-kW) 3.5-L V6 gasoline engine and a torque converter mated to a five-speed automatic transmission driving the rear wheels. The electric motor has a continuous rating of 42 kW with up to 71 kW available for short bursts. The motor will produce 182 N·m (134 lb·ft) of torque, with bursts to 280 N·m (207 lb·ft).

A 14-kW·h capacity lithium-ion battery pack is used to store the energy captured during braking or on the overrun. The battery pack can also be charged directly from the gasoline engine or from a conventional electricity supply when the vehicle is not in use. The plug-in recharge can be made using a socket located above the right-hand front-wheel arch.

The cooled battery pack is located beneath the load floor immediately behind the rear axle and has a mass of 175 kg (386 lb). Together, the control system, inverter, and motor add a further 95 kg (209 lb), giving a total mass for the hybrid system of 270 kg (595 lb). Mercedes quotes a curb mass of almost 2200 kg (4850 lb) for the 3665-mm (144-in) wheelbase models involved in the trials. A maximum permissible gross mass of 3880 kg (8555 lb) will provide a payload of around 1600 kg (3527 lb). Mercedes suggests that this is slightly less than the gross payload of an equivalent Sprinter powered by a diesel engine.

The storage capacity of the battery provides a range of about 30 km (19 mi) using electric power alone, which could provide a useful range in emissions-sensitive zones. The driver can manually select electric-only drive using a dashboard-mounted switch, provided there is sufficient charge in the battery pack. Otherwise, the Sprinter behaves like a “conventional” parallel hybrid, starting off under electric power alone and only firing up the gasoline engine when the driver wants more power than the electric motor can provide.

The power-steering pump, brake servo, and air-conditioning compressor are all driven electrically and designed to reduce their energy demands on the hybrid drivetrain by only operating when needed. The drive motor can also be used as a mobile generator, providing electrical power when driven by the gasoline engine.

The hybrid trials are due to begin this summer, and Mercedes sources suggested that it is now only a matter of time before hybrid Sprinters enter serial production both with gasoline and diesel engines.

The company has also re-introduced the Eco Start automatic stop/start system and gasoline/compressed natural gas (CNG) powered models, which were available with the previous-generation Sprinter. As before, the Eco Start system is only available with four-cylinder diesel models fitted with a manual transmission. The system automatically switches off the engine when the handbrake is applied and neutral is selected and the engine has been idling for 3 s or more. The engine is automatically restarted when the clutch pedal is pressed or the handbrake is released. Eco Start uses a conventional starter motor and costs €203 in Germany.

The 1.8-L bi-fuel gasoline/CNG engine differs from the previous model in adopting a mechanical supercharger, producing peak power of 156 hp (115 kW) and maximum torque of 240 N·m (177 lb·ft) compared with the 129 hp (95 kW) and 185 N·m (137 lb·ft) of its predecessor. The model is available with a six-speed manual transmission or an automatic option.

Depending on how much onboard CNG storage is required, Mercedes-Benz estimates that the curb weight of a Sprinter NGT (natural gas technology) is between 170 and 300 kg (375 and 660 lb) greater than a diesel-powered model. The gas tanks are installed under the floor and are said to not intrude into the load area.

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