Detroit Auto Show: General Motors' E-Flex platform

In conjunction with the Detroit Auto Show introduction of the Chevrolet Volt concept, General Motors is also unveiling an entirely new vehicle architecture that they've dubbed "E-Flex". As the name implies E-Flex is a platform for electrically driven vehicles. The key to this platform, though, is the inherent flexibility they've designed in. During the presentation of E-Flex Beth Lowery, GM Vice-President Energy and Environment talked about the future of energy supplies. GM sees diversity as one of the keys to energy independence.

General Motors has basically bifurcated their alternative fuel vehicles into two groups, those that have wheels driven by internal combustion engines and those that don't. The first group includes the hybrids like the mild hybrids sold today in the Saturn Vue and Aura. It also includes the upcoming two-mode hybrids in the 2008 Chevy Tahoe and other vehicles. The second group comprises vehicles that have no ICE mechanically connected to the wheels. E-Flex falls into the latter category. Find out lots more about E-Flex and see more images after the jump.

(Click here to see AutoblogGreen's high-resolution image gallery of the Chevy Volt and read all about the car here.)

[Source: General Motors]
The basic framework of the E-Flex platform

The E-Flex platform was designed to be adaptable to a variety of vehicle types and sizes in a way that can be built profitably and work in a world with wide energy diversity. General Motors doesn't believe that there will be any one silver bullet to the energy problem. Instead, the future energy supply will be more regionally diversified and decentralized. Energy sources will be based on what is available locally, such as solar, wind, biomass, geothermal etc. Some future vehicles will be driven by hydrogen, some by batteries, and still others for the foreseeable future will be internal combustion. E-Flex allows GM to tailor vehicles to the energy infrastructure vehicles of a given market, such as biodiesel made from wood chips in Sweden or sugar-cane ethanol in Brazil.

The lowest common denominator of E-Flex, the framework with the electric motor in place.

The first E-flex iteration, as implemented in the Volt, is a front wheel drive vehicle with a compact AC electric motor mounted low between the front wheels. A new-generation electronics package that combines the controls, charging and inverter into a single unit mounted on the motor. There are two charging ports going out to each front fender, allowing batteries to be charged at home without an external charger. This much is common to all E-Flex variants.

The lithium ion battery is mounted in the center tunnel

The version shown in Detroit and built into the Volt has a high capacity lithium ion battery pack, mounted longitudinally in the center tunnel of the car. This configuration concentrates the mass of the battery low in the center of the car, in order optimize the vehicle dynamics. It also gives the maximum impact protection to the battery, which is important for a LiIon battery.

The generator is mounted above the motor

The current configuration also has an internal combustion engine, combined with a generator that GM calls an EV range extender. The 1.0L turbocharged three cylinder is flex-fuel capable and optimized to run at constant speed. The 53 kW engine combined with the 53 kW generator can maintain and charge the battery pack. One advantage of this is that the Volt can avoid a common EV phenomenon known as "turtling". On battery-only EVs, when the charge level gets low, the output drops and the car is unable to accelerate or even maintain speed on a grade. With the E-flex range extension, the engine automatically starts when battery charge drops to a certain level and shuts off when the battery is charged. The compact engine/generator combination sits on top of the electric motor. The 12 gallon fuel tank sits in the normal location under the rear seat. This could easily be replaced by versions that run on diesel, E100, natural gas, or hydrogen based on market requirements.

The ICE is mounted between the electric motor and firewall

E-Flex also allows for other fuel systems to be used instead of the ICE range extender/battery. If battery technology reaches an adequate level of development, a battery only plug-in variant could easily be produced.

A variant of E-Flex equipped with a next generation General Motors designed fuel cell

The biggest complaint from EV1 customers was "I was tired of planning my life around my next charge". With the range extending capability of this platform, this complaint is no longer an issue. A biodiesel variant of this application might even close in a thousand mile range on a tank of fuel.

The Chevy Volt Concept built on the E-Flex platform

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