It’s an exciting time to be a tech. Driven by the need to reduce emissions and improve our use of the planet’s natural resources, automotive technology is progressing at an exponential rate. And it’s not just in improving conventional powertrains. It is the application of a lot of old ideas, made increasingly practical by advances in all areas of automotive engineering. Now what once was a sci-fi dream will soon become reality, as automobiles propelled solely by electricity will be offered in showrooms this fall.
A New Language
EVs, or electric vehicles, are not new. HEVs, the acronym for hybrid electric vehicles, have been traveling American roads for more than 10 years now. These cars use an electric motor and internal combustion engine (referred to in hybrid lingo as the “ICE”). On mild hybrids, the electric motor allows for idle stop functions as well as providing some additional power when the vehicle is under extreme load, such as accelerating on a steep incline.
Full hybrids can actually propel the car for short distances on the electric motor alone, using the ICE when needed for full performance and to keep the high voltage battery pack charged. This design is often referred to as a parallel drivetrain, because both sources of propulsion can be used to move the car down the road. While these designs help eliminate the waste of fuel caused by idling an engine while the vehicle is stopped, they are still dependent on the ICE as a main source of power to the drive wheels.
But what if we could increase the storage capacity of the battery and use something other than the engine to charge it? That is the next step in the evolution of EVs, the PHEV or plug in hybrid. This design is still a hybrid EV with one major exception. Its battery can be charged directly by plugging into the electrical power grid. This allows a different operational strategy for power flow, with the PHEV running on strictly battery power until the battery state of charge reaches a minimum level. Then, the ICE kicks in and the PHEV operates as a conventional HEV. This improvement saves even more fuel, but the ICE is still a needed part of the overall propulsion system.
OK, let’s get rid of the ICE altogether. These are the true EVs, running strictly on the electricity stored in the battery. Range is limited on that capacity, with most averaging 100 miles or so between charges.
And Then There’s the Volt
GM calls the Volt an E-REV, which stands for extended range electric vehicle. It is a true EV in the sense that all propulsion is supplied via electricity to the electric drive unit. The battery that provides that power for the first 40 miles or so is a T-shaped lithium ion battery approximately six feet long and weighing in at roughly 375 pounds. It has a capacity rating of 16kWh and is made up of 220 lithium ion cells. While the cells are outsourced, the battery packs themselves are being assembled by GM.
The battery assembly is mounted down the centerline of the vehicle. According to Frank Weber, global vehicle chief engineer with GM, “The battery is more than just an energy carrier; it’s a structural component that affects many other aspects of the vehicle.” It can be recharged in about three hours when connected to a 220-volt source or in a little less than eight hours on 110. The option to use either makes plugging into the power grid easy to do; 110 volt outlets are all over the place.
Only 40 Miles?
Why a 40-mile range when other EVs have 100 mile ranges? According to a Department of Transportation study in 2003, the commuting distance for nearly 80 percent of us is less than 40 miles. OK, so what if your trip is over 40 miles?
The Volt is equipped with a 1.4 four cylinder gasoline engine. But instead of being a parallel design, the Volt is a series design. The engine does not provide power directly to the wheels. Instead, it is attached to a 53kW generator and runs the generator to provide the electrical power to the drive unit. It does not come on until the battery pack state of charge reaches approximately 30 percent. Using one of several programmed rpm ranges, the engine will run at the steady speed best to provide power to the generator for propulsion and to maintain the battery pack at that 30 percent level until the owner can recharge. No “stepping on the gas” here.
The driveline as a whole is called a Voltec drivetrain, an evolution of GM’s E-Flex drivetrain concept. The idea is simple. Any power source can be used to drive the generator and supply electricity to the electric drive unit. This opens up future E-REV designs to the use of E85 (ethanol), diesel and biodiesel, or even hydrogen fuel cells as power sources.
And while the Volt incorporates regenerative braking to assist in keeping the battery up, neither system is designed to completely recharge the battery while driving as some HEVs do. If, on the off chance the Volt is driven down a really long hill and electricity production from the ICE and regenerative braking surpasses the vehicle’s needs, the ICE will shut down until needed again. GM, however, doesn’t think that is a likely scenario.
Additional Features
If the driver only uses the Volt to commute those 40 miles a day, the engine may never be needed. GM thought of that, too. The programming allows for the engine to run for about 10 minutes every 60 days to keep things loose and to allow time for needed onboard diagnostics to run. The fuel tank will be small, allowing an estimated increase in range of 260 miles, and will be a pressurized, zero evaporation design to help keep the fuel from going stale.
“It’s like shrink wrapping your food,” says engineer Trent Warnke. “It keeps the fuel from aging.”
Steering is, of course, electric power assist. And while I couldn’t find out for sure, I suspect the first production models will use electric resistive heating elements for heating the cabin and would not be surprised if electric compressors were used for cooling the passengers.
The instrument cluster is customizable by the driver, and a seven-inch touch screen provides for navigation and vehicle information. Infotainment and climate controls use touch sensitive controls, and of course, the car is Bluetooth ready.
Power? How about a top speed of 100 mph and a 0-60 time of just under nine seconds? And because it is electric, a stab on the pedal gives you full torque, right now, with a rating of 273 foot-pounds on tap. Remember, this is always supplied by the electric drive unit — at all speeds and under all conditions.
Do you have an iPhone, Droid or Blackberry? Then there will be an “app” for your Volt that allows you to monitor its state of charge and even program when the car recharges, taking advantage of the lower cost off peak hours will bring. You can lock or unlock the doors and even warm/cool the cabin, using the grid for power instead of the battery, and commanding it all from your smartphone.
Not Alone
The Volt is not alone in the EV market. Nissan will be debuting its BEV (battery electric vehicle), the Leaf, this fall as well. Chrysler and other manufacturers have announced EV plans of their own. These vehicles offer a solution to reducing environmental impact and freeing us from dependence on liquid fuels. Remember the oil embargo of the 1970s? If we were all driving EVs like the Volt, we wouldn’t even have noticed.
Yeah, it is an exciting time to be a tech.
