Tortoise And The Hare

The First Chevrolet Volt Came to Outrun the Toyota Prius. The New One Hopes to Kill It. A Tale of Two Plug-in Hybrids.

Tony Quiroga

ELECTRIC VEHICLES ARE MATURING THROUGH THEIR ADOLESCENCE, AND JUST LIKE IN MIDDLE SCHOOL, SOME MEMBERS OF THE CLASS ARE DEVELOPING FASTER.

Tesla and Chevrolet now have electric cars that will travel more than 200 miles per charge, but the vast majority of battery-powered cars are still limited to a 60-to-90mile range. In the next decade, the electric car promises to blossom into something that doesn’t require sacrifices in practicality or price when compared with a gasfueled car, but until the EV’s pimples clear up, we have plug-in hybrids.

With both a battery and a gas tank, plug-in hybrids strive to be everything to everyone, especially buyers who drive too much to deal with range limitations or who don’t want to spend much time plugged into a charger. The battery pack provides some electric-only operation while the gas tank and engine keep things moving when the battery is tapped. Chevrolet’s first Volt could travel 38 miles on its battery; after that, the engine would kick on to drive the car. Toyota, the leader in hybrid sales, also sold a plug-in version of its ubiquitous Prius; it featured a lithium-ion battery pack and could travel 11 miles on electric-only power before burning any gas.

Chevy and Toyota’s plug-ins are now entering their second generation, and both offer greater electric-only range and improved performance. Chevrolet’s Volt now has a larger, 18.4-kWh battery that weighs 21 pounds less than its predecessor’s, uses fewer cells, and delivers more than 40 miles of EV range. Inside the trans axle are two motor/ generators. While the combined gas and electric power output is unchanged from the previous Volt, GM’s redesign of the motors and the gearbox increases efficiency and helps the new car shed 100 pounds.

When the battery reaches a predetermined low state in the Volt, the new aluminum-block 1.5-liter four with 101 horsepower starts up. This naturally aspirated engine runs in the Atkinson cycle for efficiency’s sake and is lighter than the ironblock 1.4-liter it replaces. Even when the Volt switches to hybrid mode, the battery isn’t completely depleted. By leaving some electricity in reserve, the electric motors can add to the four-cylinder’s 101 horses to ensure that the Volt maintains the same 149 horsepower no matter the mode.

Toyota’s second-gen plug-in Prius (rechristened the Prius Prime) follows the Volt’s tack. Toyota doubled the battery capacity to 8.8 kWh, which more than doubles the range to 25 miles. The lithium-ion battery pack lives under the cargo area and powers the two electric motor/generators inside the trans axle, which can combine for 68 kW of output, or 91 horsepower. That’s a far more useful number than the old Prius Plug-In’s 51-hp electric-only effort.

When the juice stops flowing in the Prius Prime, a 1.8-liter Atkinson-cycle four with 95 horsepower makes its entrance. As in the Chevy, Toyota leaves some battery capacity in reserve to allow the electric motors to contribute to acceleration and support the gasoline engine. Unlike the Volt, though, the Prius Prime makes more power in hybrid mode than in EV mode, or 121 combined horsepower.

Although these plug-in hybrids are conceptually similar, the cars wrapped around the technology are vastly different. To help us dissect these differences and to see whose plug-in works better, we drove them together in stop-and-go Los Angeles traffic, on freeway slogs, and even into the canyons bordering the city. One emerged as a clear winner, both as something we’d like to drive and as an EV stopgap.

2. Toyota Prius Prime