GM Details Next-Generation Volt Powertrain

The completely reengineered Voltec propulsion system for the next-generation Chevrolet Volt is smaller, lighter and offers more power and efficiency than the original layout, according to General Motors Co.

The system consists of the battery, electric motor, secondary motor/generator unit, range-extending piston engine and control electronics. GM used real-world operating data from current Volts to guide the redesign, which uses new components throughout.

The system's new battery cells, co-developed with supplier LG Chem, feature a revised lithium-ion chemistry that raises storage capacity 20% on a volume basis. The second-generation Volt battery contains 192 such cells, down from 288 in the current system. The reconfigured battery is 30 lbs lighter and has a lower center of gravity for improved vehicle dynamics.

GM engineers also redesigned the main traction motor and secondary motor/generator. In the current system, the function of the latter device is to generate electricity when the battery is depleted and the range-extending piston engine is running.

In the new Voltec system, the motor/generator also can help propel the vehicle, especially during low-speed acceleration. The new configuration results in an integrated two-motor system that weighs 100 lbs less than the current layout, enhances low-speed acceleration about 20% and is as much as 12% more efficient.

The propulsion system's power inverter, which manages power flow between the battery and motors, is now built into the drive unit. GM says the revised architecture simplifies assembly and reduces size and mass.

Engineers slashed the amount of costly rare earths required in the magnets of the primary propulsion motor by more than 60%. The new motor/generator uses ferrite permanent magnets that require no rare earths.

The second-generation Volt's 1.5-liter 4-cylinder engine replaces the 1.4-liter unit used in the current Volt. GM offered no details about the engine, but it is widely expected to be more powerful and fuel efficient. The company will source the engine from its factory in Toluca, Mexico, for a year before transferring production to Flint, Mich.

GM will reveal further details about the new powertrain, including its electric-only range, when the new Volt is unveiled at the Detroit auto show in January.