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What's Voltec and how does it work?
Voltec is the name for GM’s revolutionary Extended-Range Electric Vehicle (E-REV) technology that uses electricity as its primary power source and gasoline as its secondary power source to generate electricity. Voltec can be found in the new Vauxhall Flextreme GT/E concept vehicle The main components of the Voltec electric propulsion system include a T-shaped battery pack, a 111-kW electric drive unit, and an engine generator for electricity.
What is an Extended-Range Electric Vehicle (E-REV)?
An E-REV is an autonomous road vehicle that primarily uses electric drive provided by a Rechargeable Energy Storage System (RESS) – e.g. a battery pack – but with an auxiliary onboard electrical energy generation unit and fuel supply used to extend the range of the vehicle once the RESS electrical charge has been depleted. The Opel Ampera is an example of an Extended-Range Electric Vehicle.
Basic Principle
The battery pack powers the electric drive unit, which is capable of reaching full vehicle speed and acceleration while driving the car electrically for up to 60 kilometers without using a drop of gasoline.
For trips longer than 60 kilometers, when the battery reaches its minimal state of charge, an on-board range extender in the form of a gasoline/E85-powered engine creates additional electricity to power the car for hundreds of additional kilometers. The range-extending engine serves only to create electricity to power the vehicle beyond 60 kilometers.
There is no anxiety about running out of electricity and becoming stranded.
Operation Strategy
The Voltec electric propulsion system is operated in the following four operation modes.
1. Electric Vehicle Mode (Engine Generator Off)
In the electric vehicle mode, the Opel Ampera powered by the Voltec system operates as a pure electric car. It is electrically driven for up to 60 kilometers without using a drop of gasoline. The state of charge is increased to a certain level thanks to regenerative breaking.
2. Extended Range Mode (Engine Generator On)
In this secondary mode, the vehicle seamlessly switches to extended-range mode once the battery has reached its minimal state of charge. As result, a small flex-fuel engine generator, operating at one of several optimized speeds, seamlessly provides electricity to power the Ampera’s electric drive unit while sustaining the charge of the battery in a buffer zone. Thanks to this mode, the Ampera’s drive range extends to 500 kilometers, until the battery can be fully recharged on a grid.
Control systems within the battery pack prevent it from discharging below its minimal state of charge. Controlling the battery in this way avoids fully charging or discharging the battery, which can shorten the battery’s life.
On the other hand, the engine generator does not fully recharge the battery because the objective of an E-REV is to minimize or eliminate the use of petroleum. The only way to fully recharge the battery is to plug the Ampera into an electrical outlet.
The cost of energy from electricity is about one-sixth the cost of gasoline, so plugging in the vehicle to charge the battery provides the lowest operating cost (as of March 2009).
3. Charge Mode
The charge mode begins when the vehicle finishes its journey and is plugged into an electrical outlet. In the charge mode, the battery is fully charged to its maximum capacity. An E-REV can be plugged into a standard household 230-volt or 120-volt outlet for charging. The vehicle’s intelligent charging technology enables the Voltec battery to be charged in less than three hours on a 230-volt outlet.
4. Parking Mode
Once the battery is fully charged, the Opel Ampera is ready for the parking mode for the next 60 kilometers of pure electric drive and hundreds more kilometers free from anxiety. When required, the Ampera is able to operate before it finishes its charging.
Regenerative Braking
Additional energy captured during vehicle braking (E-REVs are equipped with regenerative brakes) is converted into electricity and stored in the battery pack. The battery will continue to store energy from regenerative braking and any unused electricity created during extended-range mode operation. This energy supplements the engine generator to provide peak performance when required.
