Nissan 'harvests' new electric and hybrid cars

  • 31-Dec-2008 12:41 EST
EV mule car.JPG
­Nissan’s new electric car, slated for launch in 2010, will have a uniquely styled body. This is a development car based on the production Cube subcompact.

Nissan’s advance technology research and development strategy called the Orchard Concept is comprised of three parts: enrich R&D soil, seed and grow, and harvest. The concept is applied to four strategic technology fields: environment, safety, life onboard, and dynamic performance, on the definitive foundation of quality and cost.

“For each field, technology development is based on a clearly defined target, as set in our ‘Vision 2015,’ and detailed road map to get there,” affirmed Corporate Vice President Akihiro Otomo, a veteran of Nissan vehicle engineering and now responsible for the global Infiniti Business Unit including product development.

At the recent 2008 Advance Technology Briefing held at the Oppama, Japan proving ground, Nissan presented and demonstrated a number of “crops” being nurtured in two of the fields—environment and safety.

Of significant importance are two “mule” vehicle types, the production versions of which will be ready for harvest in fiscal year 2010, both employing enhanced laminated manganese Li-ion battery technology. Nissan, electric/electronic specialist NEC Group, and NEC Tokin have jointly established the Automotive Energy Supply Co. (AESC) to volume-manufacture the battery in a new plant at Nissan’s Zama premises. Commencing production in 2009, the initial plan is for 13,000 vehicle packs per year, to be increased to 65,000 in the future.

The new Li-ion battery family will have two types, either version identified by “2X,” meaning twice the energy-storage capacity of “conventional” Li-ion batteries for electric-vehicle application—and twice the power density for ICE/electric hybrid purposes. Nissan cited an example of the conventional: the cylindrical lithium cobalt oxide type developed with and supplied by then-partner Sony for Nissan’s micro two-seat runabout Hyper-Mini of circa 2000, a few of which are still running merrily in the hands of private owners. Nissan sold them outright with a generous industry organization-provided incentive to buyers.

Representative research of the Nissan Research Center Battery Laboratory is nano-dispersion technology that enables fine-structured electrodes with low internal electrical flow resistance. Active ingredients that store electrical energy and conductive additives providing free passage for higher power are optimally dispersed in the electrodes. Thus, the 2X energy density battery for EVs realizes 50% greater power density as well, according to Nissan.

The EV-01 and EV-02 development mule vehicles offered for sampling are based on the production Cube tall box, sharing the B-segment platform with the Versa, hinting at the production car’s size and chassis. Nissan sources say that its body and style will be unique.

The mule vehicle is front-wheel drive powered by a single transversely mounted motor. It retains five-person seating; however, the rear compartment’s floor is raised to accommodate the battery pack, “which will be flattened in the production car,” assured an attending engineer.

Performance would be on par with a car equipped with a gasoline 1.8-L L4 engine combined with a CVT, with perhaps a bit more urge on initial acceleration in utter smoothness and quietness.

So the inevitable questions must be how much—in yen, Euro, dollars—and how far—in miles or kilometers. “We are still competing in a realm of 100 to 200 km in real-life conditions, the range depending on the battery size fitting in a vehicle,” a senior Battery Laboratory engineer confided. “Further improvement in performance will be by finding and selecting new materials. There are many barriers to overcome before our ultimate goal, getting a 500-km range that competes with today’s gasoline vehicle.”

The Renault-Nissan Alliance will provide electric vehicles to the venture-backed Project Better Place, which will build electric recharge facilities in Israel and Denmark, with initial deployment beginning in 2010. The first prototype car, based on the C-segment Renault Megane, was revealed in January 2008. AESC supplies Li-ion batteries to Renault EVs.

Nissan’s second in-house hybrid system is likely to be introduced in an Infiniti car model, as predicted by the development mule car based on the previous-generation G35 midsize performance-luxury sedan. The engine in this car is the type VQ35DE 3.5-L V6 sans VVEL (variable valve event and lift) of the latest VQ37VHR unit. The hybrid system is a parallel type that operates in four modes: 1) electric drive “when driving in urban districts,” 2) engine drive, 3) engine and motor assist drive on acceleration; and 4) regenerative mode with the engine cut off and the motor/generator replenishing electric energy to the battery.

The hybrid system is an ingenious adaptation of the soon-to-be-introduced JATCO seven-speed automatic transmission for rear-wheel-drive vehicles, which marks the arrival of long-awaited extra ratios. A single dry-plate clutch and single electric motor-generator occupy the space vacated by the torque converter. The system operates with twin clutches, the aforementioned single-plate one up front and the other a normal multiplate wet one at the rear of the transmission. They alternate between the four modes, electronically controlled and automatically actuated. The planetary gearbox retains all seven forward ratios.

The mule G35 started off in the EV mode, with the front clutch fully disengaged and the engine dormant, and went through gears as in a conventional ICE/automatic manner to 80 km/h (50 mph) on the proving ground’s not-very-long stretch.

As with the EV-01/02, no specifications were given, apart from the G35DE and hybridized JATCO seven-speed combination. Judging from the mule car’s electric acceleration, the motor’s output must be about 30 kW.

How high a speed would it take, provided one does not press on the accelerator pedal, to bring the VQ35DE to life? “In this prototype, up to (American) freeway cruising speeds, going through all the gears, as long as SOC is maintained at a preset level,” responded a company engineer. He added that it was the team’s development goal in the production car.

Senior Engineer Masayuki Kobayashi of HEV Engineering Group 1 recognizes that the very elegance of the hybrid system fitting within the base transmission housing presented challenges, getting the front-clutch operation to be as smooth as expected in a performance-luxury car. The mule car still transmitted a clonk when the clutch was engaged, starting the engine. His team would be working hard toward that goal.

The secondary battery is a high-power-density version of the laminated Li-ion battery.

Nissan is conducting real-life tests and evaluation using the G35 mule in the U.S. and Japan, aiming at commercial launch of the production car in FY2010. Otomo ensured a superior performance to the base V6 model, while attaining L4 compact car fuel economy.

Further down the path is a next-generation vehicle powered by a new and enhanced fuel cell stack. The new stack is rated at 130 kW versus the 2005 version’s 90 kW and the 2003’s 63 kW, marking 3.4 times more power than the original stack.

The new stack employs stamped metallic separators with rearranged hydrogen, air, and cooling water passage grooves, enabling a much more compact and lighter package, occupying 68 L (2.4 ft3) and weighing 86 kg (190 lb).

Nissan also claims to have halved the amount of platinum, with the projected cost reduced by 35% versus the 2005 stack. Nissan explains that by increasing the amount of water and hydrogen ions in the polymer-electrolyte membrane and making movement of hydrogen ions easier, it achieved better electric power generation. Nissan’s commercialization target of the next-generation fuel-cell vehicle (FCV) is set for 2015.

The current 2005 vintage has, by the way, achieved the fastest FCV lap on the hallowed Nurburgring North Circuit, recording 11 min, 53 s, on a thoroughly wet 20.68-km course.

Nissan is also pursuing the gasoline-fueled HCCI route employing VVEL valvetrain. Otomo said that a new three-dimensional HCCI simulation program would be a powerful tool in making the combustion strategy a reality over a wide operating range. The new simulation program shortens calculations that had taken about two months to three days.

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