Ford gets smarter about hybrid technology with Fusion

  • 14-Sep-2009 06:33 EDT
graphic 2010 Fusion H.jpg
Ford engineers and other drivers took shifts driving a non-modified 2010 Fusion Hybrid for 69 h. April's Virginia/Washington, D.C., driving marathon ended with 1,445.7 miles and an average of 81.5 mpg on a single tank of gas. Fusion Hybrid's estimated EPA is 41 mpg city and 36 mpg highway.

Five years after the introduction of Ford's hybrid-electric system in a Escape compact SUV, the second-generation technology debuts in the automaker's Fusion midsize sedan.

In the timeframe after the Escape Hybrid's launch in model year 2005 and the lead up to the 2010 Fusion Hybrid's launch, braking, battery, calibration, software, and other hybrid-electric focused engineers phoned hundreds of Ford Escape Hybrid customers.

Ford engineers asked a series of questions, and the responses from Escape Hybrid drivers gave the technical folks a firsthand perspective about what worked and what could be improved. Increasing the electric-only mode limit beyond 25 mph (40 km/h) was a customer want.

The 2010 Escape Hybrid is capable of operating in electric-only mode up to 40 mph (64 km/h), and the 2010 Fusion Hybrid—which debuts the next-generation hybrid technology—has electric-only energy available at speeds below 47 mph (76 km/h).

Both the Escape and Fusion hybrid vehicles employ 5.5 A·h nickel-metal hydride batteries. "We were able to achieve that with fewer battery cells and at a lower voltage; the Escape Hybrid is at 330 volts and the Fusion Hybrid is at 275 volts," said Gil Portalatin, Hybrid Propulsion System Applications Manager for Ford.

Because the entire vehicle system was optimized, "the battery doesn't have to provide as much power. The power limits for the Fusion Hybrid are about 27 kW, compared to 39 kW for the Escape Hybrid. Even with lower battery power, the Fusion Hybrid is able to go from zero to 60 mph faster than the Escape Hybrid," said Bob Taenaka, Technical Expert, Advanced Battery System Development and Supervisor of Battery Cell Integration and Test at Ford.

A 20% increase in battery cell power is largely credited to battery-cell provider Sanyo Electric making improvements to the current collectors to elicit a resistance reduction in the electrical pathways as well as chemistry improvements in the hydride alloy, which is the negative-electrode of the cell, according to Taenaka.

As a new hybrid system feature, the variable voltage controller (VVC), provides a vital assist. "The battery now has a lower operating voltage compared to the first-generation hybrid system, and the VVC allows the voltage to be boosted up so that the other vehicle components can operate at an optimum voltage range," said Taenaka.

The Ford-developed VVC can over-boost the traction motor by 130% and the generator by 160%. Packaged within the transmission's high-voltage power electronics, the VVC boosts the voltage when battery voltage falls below a pre-determined level during specific operating conditions. "The whole point of the VVC is to use extra voltage when it is needed, such as for acceleration and during emergency maneuvers, and those are instances when the system demands the additional electrical power," Portalatin said.

Minimum battery voltage can be lowered by about 40 volts in the Fusion Hybrid compared to the Escape Hybrid. "The lower the battery voltage can go, the fewer cells that have to be put into the system. And fewer battery cells save space, weight, and cost," said Taenaka.

Fusion Hybrid uses 208 cells versus the 250 battery cells used in the 2005-2009 Escape Hybrid. When compared to the 2005-2009 Escape Hybrid's 200-lb (91-kg) battery pack, the Fusion Hybrid's 135-lb (61-kg) mass shaved 65 lb (29 kg) from the Delphi-supplied battery pack.

The second-generation hybrid system uses a 2.0 kg lighter and more efficient dc-dc converter and a 2.5-L DOHC 16-valve inline four-cylinder. The Atkinson-cycle engine produces 156 hp (116 kW) at 6000 rpm and 136 lb·ft (184 N·m) at 2250 rpm versus the previous 2.3-L engine with 133 hp (99 kW) at 6000 rpm and 124 lb·ft (168 N·m) at 4250 rpm. And the electric motor has revised air gaps between the magnets. "The gap between the electric magnets on the armature is closer, so there is less radio frequency interference," said Portalatin.

While 2010 hybrid versions of the Ford Fusion and Escape as well as sibling vehicles Mercury Milan and Mariner spotlight second-generation hybrid system technologies, the future will get a charge from a different battery type. "Lithium-ion battery technology wasn't ready for the 2010 model year, but a next-generation hybrid system will include a plug-in for the 2013 model year. The BEV (battery electric vehicle) Transit Connect commercial van arrives as early as 2010, and a BEV Focus compact car follows in 2011," said Portalatin.

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