Hybrid Volt travels same assembly line as big sedans

DETROIT — Size doesn't matter at this General Motors Co. assembly plant.

Rolling down the line in Hamtramck, Mich., one after the other, are full-sized Buick and Cadillac sedans and, from time to time, a compact Chevrolet. The odd car out is the plug-in hybrid 2011 Volt.

"Part of the whole planning cycle was to build the Volt into the process and maintain flexibility so that we didn't have a specific process or specific assembly line for the Volt," says George Dandalides, the Chevrolet Volt's launch manager.

There are only a handful of differences in the assembly process between the plug-in hybrid Volt and what might be called the conventional models assembled at the plant: the 2011 Buick Lucerne and Cadillac DTS sedans.

The Volt is propelled by a battery-powered electric motor for up to 40 miles. If the lithium ion battery runs low, a 1.4-liter four-cylinder engine kicks in to recharge the battery, extending the car's total range to more than 300 miles.

Sales begin in October or November. Chevrolet expects to sell 10,000 in 2011 and 30,000 the next year.

The Volt was designed with the Hamtramck plant in mind. The plant required only minor changes. For example, the assembly line's carriers were modified to handle the Volt's smaller body.

Dandalides says the manufacturing processes for the DTS, Lucerne and Volt "are very, very close. I won't say identical, but very, very close." Here are some of the few assembly differences:

• The Volt is a five-door hatchback; the Lucerne and DTS are four-door sedans. The plant's body shop was modified to handle both.

• The Volt, Lucerne and DTS are painted on the same line, but all Volts are produced with two-tone paint. After the primary color is applied and the paint has dried, the conveyor moves each Volt to a module. The car is masked by hand, and the second color, gloss black, is applied by computer to the roof and deck lid. The masking and paint process takes 105 minutes.

• Somewhere between a quarter and a third of the way through general assembly, the high-voltage lithium ion battery is installed.

The battery is delivered on an electrified cart that tracks underneath the vehicle. Two operators manually control the lift mechanism on the cart and raise the battery into the underside of the vehicle. Then they secure the battery.

The battery is T-shaped, running down the center between the two front seats in the tunnel area and underneath the two rear seats.

• What is called the high-voltage disconnect is installed late in the assembly process. The device separates the high-voltage battery from the car's electric motor and other electrically operated components.

"It is similar to what you would have near the air-conditioning unit at your house," Dandalides says. "There is a disconnect outside [the house] in a little gray box. You pull the little thing out, turn it 180 degrees and put it back in so you can disconnect during the winter or for service. We have a high-voltage disconnect that conceptually is similar to that."

The Volt's disconnect is under the console between the front seats.

• The Volt has more cooling and heating capacity than the Lucerne and DTS. A separate radiator in the Volt's engine compartment is connected with hoses and steel tubing to the high-voltage battery.

"The lithium ion battery does not like to get hot, and it does not like to get cold," Dandalides says. "So you are either heating it or cooling it to maintain the optimal ambient temperature." Coolant is run through passages in the battery pack.