Set to hit US showrooms at the end of the month, Honda's new Accord Hybrid milks enough fuel efficiency from its hybrid powertrain and tiny 1.3 kWh lithium-ion battery pack to achieve 50 mpg (4.5 l/100km).

The 2014 Accord Hybrid uses the same chassis and powertrain as does the Accord Plug-In, combining a 2.0 l (126 cu in) inline four cylinder Atkinson-cycle engine that provides 140 hp (106 kW) at 6,200 rpm with a 124 kW electric motor and a 105 kW electric generator driven by the gas engine. The key differences are that the Plug-In, which is currently available only in New York and California, has a much larger 6.7 kWh battery pack ... and has a starting price of over US$40K compared to the suggested $29,155 for the Accord Hybrid.

This drivetrain provides the Accord Hybrid with three main operating modes. In all-electric mode, the battery runs the electric motor at a maximum level of 42 kW (55 hp). This power level is a design limitation for the battery/motor-generator control electronics. Not only are the battery and electronics easier to cool at this power level, but they are also less expensive to purchase. The 1.3 kWh battery in the Accord Hybrid holds the energy equivalent of about half a soda can of gasoline. As a result, pure EV operations are limited mainly to initial acceleration from a stop.

In combined gasoline/electric mode, the 2.0 l engine (above) runs a generator that supplies power to a drive motor (below).

The Atkinson engine, a type of engine used in many hybrids, is about 15 percent more efficient than are more conventional Otto-cycle engines, but the user pays for this efficiency in reduced power density and less flexible operation. It's best suited to the role of generating electricity so that the electric motor can provide motive power. In combined mode, the 1.3 kWh battery pack is used to even out the power load, charging on a bit of excess power here, and providing a bit of extra acceleration there.

At higher speeds (above about 50 mph (80 kph)), the gas engine can be directly coupled to the driving wheels, providing a gas-powered overdrive. The occasional burst of acceleration can be provided by adding the 55 hp of the electric motor system.

The Honda Accord Hybrid has no transmission, despite the mention in Honda's literature and specs of an "electric continuously variable transmission." Honda is talking about the use of the gas engine-electric generator-electric drive motor chain to provide desired power levels when the vehicle is operating in combined gasoline/electric mode.

However, the electric motor is permanently locked to the driving wheels, enabling the EV-only and combined gasoline/electric modes, and a simple clutch locks the gas engine to the driving wheels in direct-drive mode. Avoiding the slippage of continuously variable transmissions is another reason the Accord Hybrid has such excellent fuel efficiency. Regenerative braking also helps, and can be set to various levels of aggressiveness.

Although the starting price of an entry-level Accord Hybrid is some $6,500 above that of an Accord Sedan, the Accord Hybrid is equipped with far more standard equipment, including Honda's Lane Watch blind spot display, a rearview camera, Expanded View driver's mirror, 17 inch alloy wheels, a ten-way power drivers seat, LED daytime running lights, multiple modes of data integration, and a 160-watt AM/FM/CD audio system. Some of the items which are standard equipment on the Hybrid are not even available on the LX Sedan, acting to make the cost of the Hybrid much more attractive.

On the other end of the price spectrum, the Accord Plug-In costs about $11.3K more than the entry-level Accord Hybrid. However, the options level of the Plug-In is about equal to that of the Hybrid Touring, a mere $5.5K cheaper. The remaining difference in price is a bit larger than usual for plug-in technology, but not offensively so.

Given that the Accord Hybrid Sedan is considered a full-size car, and that the powertrain can give 50 mpg driving in and out of the city while also enabling 7.5 second 0-60 mph times, the cost of this new hybrid seems justified. Early tests suggest that the Accord Hybrid might even get better gas mileage than the EPA figures in normal driving.

Source: Honda Motors

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