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2011 Hyundai Sonata Hybrid First Impressions

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Mike Goetz
Late to the party, but early with lithium polymer technology
Torrey Pines, California — Sometimes it’s better not to be first. Just ask anybody who has had to jump out of a WW II foxhole.

Hyundai’s late entry into the North American midsize hybrid market, with its just-released 2011 Hyundai Sonata, allowed it to see how the early combatants fared, and allowed it to utilize the latest and greatest battery technology.

On the exterior you’ll find pieces designed to lower aerodynamics and make the vehicle look more high-techy. (Photo: Mike Goetz/Auto123.com)

Lithium polymer battery pack
The Hyundai Sonata flaunts the world’s first automotive application of a lithium polymer battery pack; developed with its battery partner and fellow Korean company, LG Chem.

Its advantages over the nickel metal hydride battery packs in other midsize hybrids are many: more efficient; more compact; lighter; better cooling properties (requiring only air cooling, instead of heavier liquid cooling).

Unlike nickel metal hydride cells, or even lithium ion cells used in computers, which are cylindrical in shape, lithium polymer cells have a flat rectangle shape like a thin stack of paper. Seventy two of these rectangle cells are wired in series to produce a 1.4 kilowatt-hour battery back weighing just 94.9 pounds (versus 123.9 lbs for the pack in the Camry).

Designed for drive-ability
Hyundai notes that consumer research revealed that current hybrid drivers weren’t all that thrilled with the driving feel of their vehicle’s CVTs (continuously variable transmissions), with their highway fuel economy numbers, and with the top speed of the EV mode.

To address those issues (and others), Hyundai decided on a different “transmission” layout. Both Ford and Toyota employ a “power split” configuration: a gas engine hooked up to a CVT; the electric motor tied to the sun gear of the CVT's planetary gear set. Net result: electric motors spin higher than they would like to under some conditions (inefficient); and the top speed of the EV is limited (usually to below 60 mph).

In contrast, Hyundai basically stuck the electric motor where the torque converter would be in their new, conventional, and developed-in-house six-speed automatic transmission. An electronic clutch can engage and disengage either the gas engine or electric motor, to ultimately net three different modes: electric only, gas only, both gas and electric.

The set up also allows Hyundai to mix and match different sized engines and transmissions for future hybrid applications.

To complete the hybrid powertrain, Hyundai re-designed the 2.4-litre I4 to run on the more hybrid-appropriate “Atkinson Cycle.” It produces 166 hp and 154 lb-ft of torque.

The electric motor produces the equivalent of about 40.2 hp.

To complete the hybrid powertrain, Hyundai re-designed the 2.4-litre I4 to run on the more hybrid-appropriate ''Atkinson Cycle.'' (Photo: Mike Goetz/Auto123.com)
Mike Goetz
Mike Goetz
Automotive expert