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VW’s Golf Variant twinDRIVE Undergoing Testing in Europe
Volkswagen will market several plug-in hybrids in 2013-2014 as well as a pure electric VW up! It recently unveiled the Golf Variant twinDRIVE prototype. Twenty of these PHEVs will be used in VW's ‘Fleet Study in Electric Mobility.’ VW, with six partners and the German Ministry of the Environment, is investigating the use of renewable energy sources for electrically powered vehicles. Initiated in July 2008, the project runs until July 2012.
This parallel hybrid has a 114 horsepower electric motor, a 1.4-liter TSI gasoline direct-injection engine supplying 114 horsepower, and a 30 kilowatt generator, all housed in the engine compartment. The battery pack and high-voltage power distribution unit are located in the rear. A DC/DC converter converts high voltage from the battery pack to 12 volts for the regular electrical system. Engine heat assists the electric heating system in cold weather.
Two different lithium-ion battery systems are being tested. Ten Variant twinDRIVEs are equipped with batteries from the American-German manufacturer GAIA and 10 use batteries from Korean-German joint venture SB LiMotive (Samsung and Bosch). The GAIA cathode type battery consists of 86 cells and a capacity of 11.2 kilowatt-hours. The SB LiMotive cathode type battery has 84 cells to supply 13.2 kilowatt-hours. Both high power and energy density batteries weigh about 330 pounds. A battery management and monitoring system keeps the batteries cool.
The Golf Variant twinDRIVE has three operating modes. In urban driving, it operates on the E-Motor with an electric-only range of 35 miles and a top speed of 75 mph. When more power is needed, the internal combustion engine is started. The TwinDRIVE features a single-speed transmission and an electronically actuated ‘separation’ clutch between the TSI engine and E-motor. At speeds above 31 mph, the separation clutch closes and the TSI is directly coupled to the drivetrain for efficient driving with the internal combustion engine alone. With the gasoline engine, the total range is 558 miles with a 105 mph top speed. VW claims 112 U.S. mpg (2.1 liters per 100 kilometers). When maximum acceleration is required, the E-Motor and TSI together provide up to 161 horsepower so it can accelerate from 0 to 62 mph in under 12 seconds.
The internal combustion engine can be started by the driver whenever needed to charge the battery via the generator or provide additional drive power. The driver can manually choose the pure E-MODE provided the battery is sufficiently charged. During regenerative braking, the TSI engine is turned off and the separation clutch is open so braking energy is recouped by the generator to charge the battery.
Volkswagen is developing a ‘Charging Manager’ to optimize charging so the battery is charged cost-effectively and with electricity generated from renewable sources whenever possible. When the battery is fully charged, the strategy is to maximize the share of pure electrical energy used for driving. On mid- to long-range drives, the intelligent hybrid management system automatically optimizes load distribution between the E-Motor and gasoline engine to minimize fuel consumption based on the current route and situation. The vehicle could also feed electricity back into the electrical grid to temporarily offset fluctuations in the grid.