Cars that use battery power are becoming more common, but not all of them are meant to run on electricity alone. Some automakers, including GM, are adding electric motors to gasoline engines to provide a conventional level of power with lower fuel consumption.


A new system called eAssist will be available later this year on the 2012 Buick LaCrosse and Regal.


“It will be more than a 25 per cent (fuel economy) improvement over the 2011,” says Daryl Wilson, lead development engineer for LaCrosse and Regal eAssist.


The vast majority of the improvement will be from the eAssist, and the rest from aerodynamic improvements and more fuel-efficient tires.


Called “light electrification” technology, the system includes a small electric motor-generator attached to the gasoline engine, and a 29-kilogram power pack containing a lithium-ion battery and power inverter.

When you’re driving a conventional car and you press the throttle to get more power, such as when passing, the engine works harder and so uses more fuel. With eAssist, the electric motor provides up to 15 horsepower to the engine, which doesn’t have to work as hard. Since electric motors make their full power as soon as they start up — as opposed to a gasoline engine, which has to rev up — that extra boost of power is immediately available when you press the throttle.

Like a hybrid, the eAssist system shuts off the gasoline engine at idle, such as when sitting at a red light (the lights, heater and stereo continue to operate) and starts it up again when you’re ready to take off.

“Another key feature is that we cut fuel to the engine during deceleration,” Wilson says.

“We do this at high speeds in all GM cars, but this one can be done right down to zero, enabled by the ability to smooth torque disturbances with the electric motor as you’re getting down to lower speeds.”

While eAssist can’t run the car on battery alone, it’s not as complex or expensive as a full hybrid system.

The battery, generally the priciest component, is about one-third the size of a typical hybrid battery, Wilson says, “and the electric motor is also significantly smaller. We’re able to pack that where an alternator normally goes, which requires less infrastructure and change to integrate it.”

The eAssist system doesn’t get plugged into a wall outlet. Instead, the system recharges itself by capturing energy during deceleration and braking, and converting it to electricity that’s stored in the battery.

The main thing, Wilson says, is that although the car is electrically assisted, it feels virtually the same as driving a regular Buick.