GM Voltec powertrain
|GM Voltec platform|
|Body and chassis|
|Class||Extended-Range EV (EREV)|
|Vehicles||Chevrolet Volt, Cadillac ELR, Holden Volt, Opel Ampera, Vauxhall Ampera|
Voltec, formerly known as E-Flex, is a General Motors powertrain released in November 2010. The Voltec architecture is primarily a plug-in capable, battery-dominant electric vehicle with additional fossil fuel powered series and parallel hybrid capabilities. 
Voltec vehicles like the Chevrolet Volt are all electrically driven, feature common drivetrain components, and will be able to create electricity on board using either a fuel cell or a gasoline motor to generate electricity. Regenerative braking contributes to the on-board electricity generation.
The Voltec drivetrain was initially demonstrated as E-Flex in the 2007 Chevrolet Volt concept vehicle that appeared in the North American International Auto Show which introduced the E-Flex drive system as an attempt to standardize many components of possible future electrically propelled vehicles, and to allow multiple interchangeable electricity-generating systems. The initial design as envisioned in the Volt combines an electric motor and 16 kWh (58 MJ) lithium-ion battery plug-in system with a small engine (1.4 liter) powered by gasoline linked to a 55 kW (74 hp) generator. The initial production Volt will be propelled by an electric motor with a peak output of 111 kW (149 hp). Ordinarily, the Volt would be charged while at home overnight (plug-in hybrid-mode) through a charging port. A full charge reportedly takes 10 hours from a standard North American 120 V, 15 A household outlet, or 4 hours from a 240 V 15 A SAE J1772 electrical vehicle supply.
Since the electrical drivetrain is not affected by the method used to charge the batteries, several options could be available for acting as an electrical power source. The primary configuration specified in the Volt promotional literature uses a turbocharged 1.0-liter engine with three cylinders, a flex-fuel engine capable of running gasoline or E85 (85% ethanol, 15% gasoline).
Other engine-driven power options would be a pure ethanol (E100) engine, a diesel engine capable of running biodiesel fuel, or even a hydrogen fuel cell, once that technology becomes practical. (The Ford Airstream concept, which debuted at the same show, uses a fuel cell plug-in hybrid design.)
Another power-source option, one that does not rely on an internal-combustion engine at all, was demonstrated in the Volt fuel cell concept vehicle, which appeared at the 2007 Shanghai Auto Show. Due to the high cost of fuel cells compared to newer lower cost lithium batteries, General Motors has publicly suggested that the Volt will not be using fuel cells in any near term production vehicles.
The general layout of the initial production platform is considered by some to be a plug-in series hybrid design since mechanical power initially drives the generator, which in turn charges the battery pack. Power is then drained from the batteries to run the electrical motors which move the vehicle. The internal combustion engine can run at a constant speed for both optimal efficiency and mechanical simplicity (i.e., there is no need for a multi-valve, multi- or variable-cam design). The Voltec, like the Prius, uses a planetary gearset to couple power from two sources to the wheels. Unlike the Prius, the Voltec only rarely drives the wheels with mechanical assist from the engine. The Voltec could therefore be considered a power-split hybrid.
The lithium-ion battery in the initial Voltec production vehicle is kept in a state-of-charge (SOC) range of between 30% and 80%, with the on-board generator that works to maintain the battery at the 30% charge level.
GM has decided on a new descriptive terminology distinct from calling it a hybrid. They are calling the Volt an E-REV, for "extended-range electric vehicle". At high demand in charge sustaining mode, both the electrical motor and the motor generator simultaneously drive the wheels. In this mode, the internal combustion engine is connected to the planetary transmission through the motor generator.
GM chose its Global Delta II compact vehicle architecture for its first Voltec application, the Chevrolet Volt. Production began in November 2010 with the first Volts delivered to retails customers in December 2010
Slated for production
In April 2010 Chevrolet announced possible intent to produce a larger Volt variant, the MPV5 crossover design which can carry five people. In addition, the 180.5-inch long vehicle has a 30.5 cubic feet (0.86 m3) of cargo space behind the rear seats, 62.3 cubic feet (1.76 m3) when those seats are folded down. In August 2011, GM confirmed the production version of the Cadillac Converj, with the new name Cadillac ELR. GM announced that they will present the 2014 Cadillac ELR production vehicle to the general public at the 2013 North American Auto Show in Detroit in early January.
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