Chevy has set a new precedent for affordable, long-range EV driving and performance with the new 2017 Bolt EV.
Revealed at the ongoing Detroit Motor Show, the Bolt EV’s engineers developed its propulsion system to offer more than an estimated 320km and a driving experience that’s more akin to a compact sports sedan than a small utilitarian crossover.
“Being the leader in range and affordability means nothing if the car isn’t going to excite you each time you get behind the wheel,” said Josh Tavel, Chief Engineer, Chevrolet Bolt EV. “That’s why the team was tasked with delivering a propulsion system that would also make the Bolt EV an electric vehicle that owners would love to drive.”
Gear configuration raises power delivery
Like most EVs on the road, the Bolt EV’s drive system uses a single high-capacity electric motor to propel the car. But it’s the smooth, powerful and quiet motor design, gear configuration and shift-by-wire system that separates it from the pack.
The engineering team designed the Bolt EV’s electric motor with an offset gear and shaft configuration tailored to meet efficiency and performance targets – most notably more than an estimated 320km of range. The motor is capable of producing up to 36.7kgm of torque and 200bhp of motoring power. Combined with a 7.05:1 final drive ratio, it helps propel the Bolt EV from 0-96kph in less than seven seconds.
Power delivery is controlled by Chevrolet’s first Electronic Precision Shift system. This shift and park-by-wire system sends electronic signals to the Bolt EV’s drive unit to manage precise feel and delivery of power and torque, based on drive mode selection and accelerator inputs. A by-wire shifter requires less packaging space than a traditional mechanical shifter, resulting in more interior space and improved interior layout.
Collaboration on battery helps push range
Having more than two billion kilometres of EV experience from the Chevrolet Volt helped Bolt EV battery engineers and strategic partner LG Electronics to develop an all-new cell and battery pack to offer more than an estimated 320km of range.
Battery system preliminary specifications include:
• 60kWh lithium-ion battery pack
• 288 lithium ion cells
• Five sections
• 10 modules
• 96 cell groups – three cells per group
• 435kg total weight
“You usually have a battery cell that delivers either the desired levels of energy or power, but not traditionally both. With this cell design and chemistry we were able to deliver a battery system with 160kW of peak power and 60kW hours of energy,” said Gregory Smith, Battery Pack Engineering Group Manager, Bolt EV.
The battery uses active thermal conditioning, similar to the Chevrolet Volt, to keep the battery operating at its optimum temperature, which results in solid battery life performance. The Bolt EV battery will be covered by an 8-year/ 160,000km (whichever comes first) limited warranty.
Inside the battery pack
The battery pack that spans the entire floor, from the front foot well to the back of the rear seat – is a new cell design and chemistry. The nickel-rich lithium-ion chemistry provides improved thermal operating performance over other chemistries, which requires a smaller active cooling system for more efficient packaging. The chemistry allows the Bolt EV to maintain peak performance in varying climates and driver demands.
The cells are arranged in a ‘landscape’ format and each measures 100mm high and 338mm wide, providing improved packaging underfloor. The lower profile cell design enables the vehicle structure team to maximise interior space.
The battery system is mated to a standard equipment 7.2kW onboard charger for regular overnight charging from a 240-V wall box. A typical commute of 80km can be recharged in less than two hours. The Bolt EV also features an optional DC Fast Charging system using the industry standard SAE Combo connector. Using DC Fast Charging, the Bolt EV battery can be charged up to 145km of range in 30 minutes.