Chinese maker shows driveable prototype plug-in hybrid

  • 11-Apr-2008 02:52 EDT
byd F6.jpg
BYD Auto demonstrated a prototype of its F6 DM, a low-priced plug-in hybrid, at the 2008 North American International Auto Show (NAIAS) in Detroit.

Could BYD Auto, one of the world's smallest car companies, be the first to market a low-priced plug-in hybrid? At the 2008 North American International Auto Show (NAIAS) in Detroit, t­his privately owned Chinese company showed a prototype and announced an October introduction date, and those attendees who focus on this technology area did not question the likelihood. "The claims they make are credible," an industry executive in the hybrid battery field told AEI.

­BYD is one of the world's largest makers of rechargeable batteries, with large shares of the market in cell phones, digital cameras, and other small electronics.  And in addition to nickel metal-hydride (NiMH) batteries, it also makes the lithium iron phosphate type—LiFePO4, which is related to lithium-ion technology—including the pack installed in the prototype plug-in hybrid. One or more types from the lithium ion family of batteries, with their far more favorable power-to-weight ratio, is likely to displace the NiMH now used.

BYD entered the auto industry by purchasing a small Chinese carmaker, Tsinchuan Automobile, in 2003. Sales have been a modest 100,000 economy sedans since 2006, but production capacity is up to 300,000 units. And a massive expansion is underway, according to an American automobile importer who recently visited the company's facilities. BYD has more than 100,000 employees.

BYD Auto not only showed the prototype, but Chairman Wang Chaunfu actually drove it briefly (in electric-only mode) around the exhibit area adjacent to his NAIAS exhibit. The system is in the BYD F6, a new 4858 mm (191 in) long four-door sedan. Curb weight with the 200-kg (441-lb) battery pack is 1800 kg (3968 lb). Chairman Wang said the plug-in hybrid system would add $6000 to the cost of any of its conventional models, including the smaller F3 sedan.

The BYD hybrid battery pack is rated at 20 kW (27 hp).  Other companies have devoted much development time to the lithium cobalt oxide (LiCoO2) type of battery because of its inherently greater conductivity. However, the LiFePO4 battery is made of lower-cost materials and is inherently more resistant to breakdown from short circuits and high temperatures than LiCoO2.  Further, "doping" the lithium iron cathodes with the positive ions of other metals has been shown to dramatically increase the cell's conductivity, with some companies claiming LiFEPO4 now may be the superior choice. Greater conductivity translates to a higher rate of charge and discharge, important characteristics for an electric vehicle. A BYD associate told AEI that the company has a proprietary doping "recipe."

The pack is rated for 2000 cycles, which is the equivalent of about 100,000 mi (161,000 km). This number is at a midpoint of the advanced designs of this type. Major questions exist, however, such as whether BYD is capable of stepping up from small format to large format, which "has its challenges in terms of quality and performance," according to the hybrid battery executive. This executive and others also asked whether the battery pack would have the 8-10 year life that is expected for a hybrid that is sold in the U.S. market. Many lithium ion batteries rated for an equal or even-greater number of cycles and power have a lifespan of less than five years.

A BYD Auto associate told AEI that the plug-in hybrid would be produced only in small numbers at first, for sale only in the Chinese market. Chairman Wang said the complexities of entering the U.S. market, including the setup of a dealer organization, passing safety and emission tests, etc., put a U.S. introduction 3-5 years off.  The prototype meets Euro IV in hybrid mode, and exceeds it when all-electric mode is included, BYD states.

The F6 plug-in hybrid accelerates from a stop only on its 75-kW (101-hp) electric motor. At mid-throttle it switches to series hybrid operation, whith the engine charging the battery pack, and at high speed it operates as a parallel hybrid, using both its 1.0-L three-cylinder 50-kw (67-hp) engine and the electric motor. Top speed is 160 km/h (99 mph). Range is 100 km (62 mi) on battery charge alone, 330 km (205 mi) in hybrid mode. BYD Auto rates the powertrain as being capable of a 30% grade.

BYD also manufactures its own electronic controls, and a spokesman said this capability enabled it to more quickly integrate the system into ­a car. Because lithium ion batteries cycle within a relatively narrow range, that is, they cannot repeatedly deep cycle and recover, precise electron­ic controls are required.

The F6 plug-in hybrid has a dual external charging connector, one for quick charging that delivers a 50% charge in 10 min, and the other for household current charging, which delivers a 100% charge in nine hours.

Other companies also are developing "doped" lithium iron phosphate batteries. An advanced type developed by A123 Systems reportedly is under consideration for the forthcoming Chevrolet Volt plug-in hybrid from General Motors­.

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