Wednesday, January 13, 2016

12 Things to Know About Chevrolet’s $30,000 Bolt EV

In the race to build an affordable long-range EV, it's been a two-horse contest of late: GM versus Tesla. With the appearance of the production Chevrolet Bolt at both CES and the Detroit auto show in early January, the General has pulled ahead by a considerable length—Tesla has yet to publicly show even a concept version of its Model 3 sedan. But GM's expediency didn't translate to cut corners: The Bolt looks very promising, with a price starting at roughly $30,000 after tax credits, nationwide availability, and more than 200 miles of electric range. Here we present the essential facts before the Bolt shoots out of the starting gate later this year—silently, of course.Use of aluminum for the doors, hood, liftgate, two front crossmembers, and the front suspension control arms, plus high-strength steel for the unibody, yields a claimed 3580-pound curb weight, which is key to the Bolt's range and acceleration performance.GM claims acceleration from 0 to 60 mph in less than seven seconds, a top speed of 91 mph, and 200 miles of driving range between charges.GM’s partner, LG Chem, manufactures the battery cells and electric motor in Incheon, Korea. The motor and transaxle are assembled in Korea, then shipped to GM’s Lake Orion, Michigan, assembly plant.The Bolt’s synchronous AC drive motor is a GM design. The hollow-section rotor spins concentric with the differential’s output shafts. Two stages of helical reduction gears drop rotor rpm on a 7.05:1 overall drive ratio.The Bolt’s claimed 0.312 aerodynamic drag coefficient and modest 25.8-square-foot frontal area help this electric cut through the air with minimal ruffle.The Bolt’s 94 cubic feet of passenger space matches that of the Tesla Model S. Three rear-seat passengers sit in chair-like comfort above the battery pack. The Tesla provides substantially more cargo room: 26 cubic feet versus the Bolt’s 17. For reference, the Tesla is 32 inches longer and 8 inches wider than the Bolt.According to GM North American president Mark Reuss, the battery pack’s cost of $145 per kWh of energy capacity is comparable to Tesla’s claim. That cost multiplied by a rated capacity of 60 kWh yields a total pack cost of $8700, approximately one-quarter of the car’s total retail price ($37,500 before a $7500 federal tax credit is applied).The 960-pound battery pack consists of 288 LG cells and 10 modules packed inside a steel and plastic box that serves as a structural member that contributes 28 percent of the car's total torsional rigidity. What GM calls a cold plate in contact with the bottom of the cells circulates coolant to keep the batteries’ operating temperature in the desired range.To forestall puncture wounds that could prompt an electrical short, the Bolt’s battery pack is supported by five substantial cross members and a secure bottom cover, both made of steel. The cold plate and cell containers add more damage protection. Electronic controls are the final stage of catastrophe avoidance.The Bolt’s nickel-rich battery chemistry is tailored specifically for electric-car use, which are different from the needs of Chevrolet's mainstream plug-in hybrid, the Volt. One specific Bolt advantage is higher energy density (by both mass and volume).Using a DC fast-charge source, 90 miles of Bolt range can be replenished in 30 minutes. Using 240-volt AC power, it takes two hours to restore 50 miles of range. A fully depleted battery takes nine hours to recharge.Never mind its hatchback-like size and shape, GM executive chief engineer for electrified vehicles Pam Fletcher would prefer you consider the Bolt a crossover vehicle. Don't crossovers have to offer all-wheel drive? Asked when or if AWD—readily achievable by adding a second electric propulsion unit in back—will appear to support that label, her answer is that “anything’s possible.”
from Car and Driver Blog

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