(Warren, MI, April 28, 2009) On January 7, 2007, then General Motors Vice Chairman Bob Lutz drove onto the stage in a concept car meant to reverse all the bad publicity caused by the termination of the EV1 electric car program three years earlier. The Chevrolet Volt was conceived as a new kind of electric car that would address the practicality and range limitations of it battery powered predecessor.
By adding a small gasoline/ethanol fueled engine and generator, the extended range electric vehicle (ER-EV) would eliminate the range anxiety inherent in operating an electric vehicle in the real world. Over the course of the 28 months since the concept was revealed to the world, GM made the decision to move the Volt to production status and began an intense period of production engineering.
Through the course of 2007 and 2008, GM engineers, scientists, designers, and technicians have tested lithium ion batteries from at least two companies, redesigned the car into a production ready form, and built two generations of development prototypes. The first generation mule vehicles based on the 2007 Chevrolet Malibu body shell were built in the second half of 2007.
The earliest examples dubbed Mali-Volts were used to verify that the combination of a small engine/generator combination providing electrical energy to a drive motor could work to propel the vehicle. Through the first several months of testing the cars only had a small hybrid battery pack that acted as a buffer between the range extender (the engine and generator combination) and the drive motor.
Around the same time that these vehicles were being tested on the track at GM's Milford Proving Ground, the first lithium ion battery packs were being delivered from suppliers, LG Chem and A123 Systems for testing at the GM Tech Center in Warren MI. The first of those packs were installed into Mali-Volts in April of 2008 for road testing. In the fall of 2008, approximately 30 second generation prototypes were built up based on the smaller Chevy Cruze body that had just been revealed. The Cruze is a compact sedan that went on sale in South Korea late last year and will launch in the US market in spring 2010. The Cruze is based on the same global compact car platform that will underpin the production Volt, so it provides a good base for testing Volt hardware.
These second generation mule vehicles have been running with powertrain hardware that is currently about 80 percent representative of production hardware throughout the winter months. Some of the engineers using these vehicles are working on the control software for the powertrain that will help ensure that the battery lasts for ten years and still delivers a plug-in range of 40 miles. Others are working on the ride and handling, braking and other systems.
During our visit to the GM Tech Center GM brought out two of the Cruze mules for the group of journalists to drive around a two mile loop on the campus roads. The cars were equipped with the full Voltec powertrain including the LG Chem battery pack, and range extender. However, for our drive, GM disabled the range extender functionality so that we could experience the electric drive capabilities. The Cruze based mules are similar in size and only slightly heavier than the production intent Volt so in general the performance is similar.
The propulsion motor in the Volt has an output of 110 kW which combined with the instantaneous 273 lb-ft of torque launches the Volt to 60 mph in a spirited 8.5 seconds. A steady rain was coming down during our drive and speeds on the tech center campus are limited to 35 mph. Nonetheless, the acceleration of the test car felt strong and easily competitive with any other vehicle in the segment.
The car that we evaluated didn't have fully representative ride and handling characteristics as that work is being done on some of the other mule vehicles. However, some of the behavior of the Volt is inherent even in this car. The 400 lb mass of the battery pack is concentrated low in the chassis and toward the middle of the car. As a result the center of gravity of this Cruze is actually lower than the standard model. That low and central mass will actually be beneficial to the handling of the Volt. Body roll of the mule was minimal and ride quality over some bumpy pavement was acceptable even on the low rolling resistance tires.
We covered a total of about 12 miles around the Tech Center entirely on electrical power with headlights, window defoggers and heater running. The car ran smoothly and silently much like any other electric vehicle. Notably, GM has made efforts to cut the whine characteristic of many electric motors including the one in the old EV1. The battery pack is compact enough that it doesn't really seem to intrude on the interior volume of the car at all.
The braking system is based on the electro-hydraulic system used in the Chevy Tahoe two-mode hybrid and allows for full blending of friction and regenerative braking. Like most electric vehicles, the Volt uses a single speed gearbox that is essentially just a reduction gear. There is still a conventional PRNDL shift lever, but during driving acceleration is completely seamless.
With the shifter in D, lifting off gives only light regenerative braking similar to the coast down deceleration experienced in a conventional automatic transmission vehicle. When shifter is moved to Low, the amount of regen during throttle lift is increased to about 0.25-0.30 g, similar to what a conventional car would get from a downshift or two or the light braking typical of most driving. Posawatz explained that a driver in stop and go traffic could use L and most drive with just the accelerator, thus maximizing regen and range.
While the Cruze is nominally a five passenger car, like most compacts, the rear is really only wide enough for two passengers. Since the battery tunnel extends back into the rear, the center position becomes largely unusable. The production Volt will only have four seats available so this is not a problem.
Posawatz explained to the media in attendance that GM would start final assembly of the so-called Integration Vehicle Engineering Release (IVER) prototypes during the final week of May. This is the final prototype stage for the Volt before pre-production models start rolling off the assembly at the Detroit-Hamtramck assembly plant in early 2010. GM will be building 75 IVER prototypes with most of the parts coming off production tooling.
The IVER vehicles are largely production representative including the production body shells. The bodies in white have already been completed and other components and systems are being delivered to GM facilities over the next several weeks. These vehicles will be used to finalize control software and calibrations as well as other systems.
Posawatz explained that it's still too early to discuss pricing of the Volt when it launches in November 2010. He did however emphasize that the current federal tax credits allow for the full $7,500 rebate on a 16 kWh plug-in like the Volt. The tax credit program covers the first 200,000 unit sales from an automaker which is expected to more than cover the entire production run of the first generation Volt.
Engineers at GM are already working in parallel on the second generation of the Voltec powertrain. The main focus of generation two is bringing down cost, allowing the system to be more widely applied. General Motors is also experimenting with using some of the in-vehicle technology such as OnStar to allow for remote downloads of vehicle software updates. In much the same way that firmware for cell phones and other devices can be used to improve performance and features, OnStar downloads could improve the powertrain controls and battery management software to improve range, performance and battery life. In the coming months as the IVER vehicles are completed, GM has promised further drives in the new vehicles allowing us to experience the range extender in action as well as the new control interfaces.
For now the Volt engineers appear to be on track to meet the Job 1 target for Volt in late 2010.
