The 2016 Volt: Achieving Efficiency
The second-generation Chevrolet Volt is an overachiever in all aspects as the dedicated team at General Motors have worked to give more energy—literally and figuratively—to the compact sedan.
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On the evening of September 29, Elon Musk unveiled the production Model X electric SUV. There were but a handful of cars.
Meanwhile, about 39 miles north of where Musk was making his presentation, Pam Fletcher, General Motors’ Executive Chief Engineer—Electrified Vehicles, said that on that very day, car haulers were leaving the Detroit-Hamtramck Assembly Plant with Volts on board. A single commercial car hauler can accommodate more vehicles than Musk delivered that evening (six).
And while the price of the Model X was on the order of $132,000 for those getting the Signature Series Model X (the prices will eventually go south once there is greater capacity and the more economical versions will not have a “performance motor”), the starting MSRP for a 2016 Chevrolet Volt, including an $825 destination fee but not subtracting any tax credits, is $33,995. This means for the price of one of those initial Xes you could get three Volts and have enough left over to keep them all in fuel for a long time to come: according to the EPA testing, the Volt can drive 53 miles on electricity alone and then after the 18.4-kWh lithium-ion battery is depleted, the “range extending” 1.5-liter four-cylinder engine (that operates as a generator for the vehicle’s motors) comes into play and it has a combined EPA-estimated fuel efficiency of 42 mpg. (The electric-alone portion is rated at a combined 106 MPGe.)
So, given the battery pack and the range extender (which, incidentally, runs on regular unleaded, not premium as its predecessor requires), Fletcher suggests, that the median Volt driver will go 1,500 miles between fill-ups. No, this doesn’t mean that the Volt has a ~1,500-mile range but that they’ve determined that given the charging behavior of the Volt owners they’ve studied, based on information accumulated through OnStar, that’s the sort of range they go before they need to get to a gas station, having availed themselves of electricity along the way.
The total driving range for the 2016 Volt without the periodic electrical top-offs is 420 miles (the gas tank has an 8.9-gallon capacity).
(The Model X—which is brought into the picture here primarily because of the coincidence more than anything else—is fitted with a 90-kWh battery pack and has 250 miles of all-electric range.)
Speaking of the second-generation Volt, Fletcher says, “This is an efficiency story.” Efficiency right across the board.
The first-generation vehicle was a model year 2011 car. And the team that developed that one pretty much stayed intact and set to work on what has become the 2016 model.
Not only were they able to access vehicle information from OnStar (drivers were able to opt in to the program), but Fletcher explains that they spent a lot of time talking to customers. “They told us what they loved,” she says. “And they told us what we needed.”
She adds, “We gave them more of what they loved.”
One of the things they loved was electric range. So that was a key development target.
You might think that the way to achieve more electric range would be to add more batteries in the 5.5-ft long T-shaped housing (like
the one used in the first-generation vehicle, albeit one made of a more-robust and cost-effective SMC material from Continental Structural Plastics, which also supplied the original, and one with an integrated tray seal). GM engineers along with those from supplier LC Chem actually did something more clever than that: they revised the chemistry for the lithium-ion batteries. As a result, they were able to reduce the number of prismatic cells in the battery, from 288 to 192, while increasing the battery capacity, from 16 kWh to 18.4 kWh. That’s approximately a 20% improvement. In addition to which, they were able to reduce the mass of the overall battery by some 20 lb., and Fletcher points out that because there are fewer cells, there are fewer connections, which can result in higher reliability.
If this is an “efficiency story,” then one might think that the way to eke out more from the “range extender,” a.k.a., the internal combustion engine, would be to have a smaller engine under the hood. Yet that’s precisely what they didn’t deploy. Whereas the first generation vehicle has a 1.4-liter DOHC I4 that produces 84 hp, the 2016 Volt has an Ecotec 1.5-liter DOHC I4 that produces 101 hp. As previously noted, the 1.5-liter engine provides 42 mpg; the 1.4-liter provides 37 mpg.
The electric portion of what’s called the second-generation “Voltec electric drive system” offers more—as in a 12% efficiency improvement—and less—as in being 100 lb lighter than the first-generation system. It is a two-motor drive unit that has been engineered so that there is motor power (the two combine for 111 kW) that is best suited for the application. For example, there can be a single motor used for low-speed driving, a split between two motors during moderate operation, and both when high speeds are required.
Fletcher says that the Volt customers were interested in more spirited driving. And the drive unit responds, by improving the 0 to 30 mph acceleration to 2.6 seconds (a 19% improvement) and the 0 to 60 mph to 8.4 seconds (a 7% improvement). (The previously mentioned Model X: 0 to 60 in 3.2 seconds.)
One concern that some had expressed as regards the electrification of vehicles was the demands for rare earth elements for the motors which are, well, rare (or not readily available or expensive or both). For the 2016 Volt, one of the motors uses little and the other uses none.
One important simplification that they did in developing the new system is integrating the Traction Power Inverter Module, which manages the power flow between the battery and the drive motor, into the drive unit. Through the integration, they were able to eliminate the large orange wires under the hood.
And another thing they wanted was fresh, contemporary styling that didn’t call attention to the fact that it is an extended-range electric vehicle, Fletcher says. While the front fascia has metallic upper and lower grille panels that resemble the first generation vehicle, and while there is still the logo near the bottom of the A-pillar, the second-generation car is far more sculpted in terms of body side treatments and more sweeping in the backlight area. On the inside there is a shift away from the iPod-inspired first-generation (although it should be noted that the new car offers Apple CarPlay) toward something that is more akin to what would be found on the inside of, say, an Impala.
Final assembly for the Volt, as previously mentioned, is at the Detroit-Hamtramck Assembly Plant. The lithium-ion battery pack assembly is also performed in Michigan, at the Brownstown Battery Assembly Plant, and the drive unit at the GM Powertrain Plant in Warren. For the first year, the 1.5-liter range extender is being manufactured at the GM Toluca, Mexico, engine plant, but that will be shifted to the GM engine plant in Flint, Michigan.
Pam Fletcher puts it plainly about the 2016 Volt: “Gen II is better in every way. That’s no ________.”
Yes, she believes it, knows it, that emphatically.