Article and photos by Jim Kerr
Hybrid vehicles have been attracting a lot of attention in the last couple of years with Toyota, Honda, Ford and Lexus producing vehicles with this technology. GM introduced their Parallel Hybrid Truck, a 1500 series pickup a couple years ago, but this was not a true hybrid. It didn’t use the electric motor/generator to propel the vehicle – only to start the engine after it was stopped or generate power for the 110- volt outlets. Now GM is ready to introduce their first real hybrid and it is different than anything else on the road.
GM calls it a BAS system (Belt/Alternator/Starter). The BAS hybrid system will be introduced first in the 2007 Saturn Vue Greenline later this year and will follow shortly in the 2008 Chevrolet Malibu. This system is a “mild” hybrid. It uses a special generator/motor unit
instead of the conventional alternator bolted onto the engine and it turns the engine’s crankshaft through a wider serpentine drive belt on the front of the engine. Add an electronic controller, battery pack and gauges for the driver and the system is complete. It is a compact system that looks like it could be easily added to any vehicle with minimal changes to the existing vehicle.
The four-cylinder gasoline engine still has a conventional starter but uses the generator/motor unit to start the engine most of the time. During acceleration, power is provided by both the gasoline and electric motors, although the electric motor can move the vehicle by itself at very slow speeds. Electric motors produce very high torque at low speeds and this electric motor can provide 115 lb.-ft. of torque to move the vehicle from a stop and start the gasoline engine. The electric motor can also provide up to 300 watts of continuous power to assist the gas engine during cruise or acceleration operation. Combined, the gas engine and electric motor put out 170 horsepower, with an estimated 10 to 20% fuel economy savings over conventional vehicles.
2007 Saturn Vue Green Line. Click image to enlarge
During deceleration, the generator/motor unit provides regenerative braking, recharging the 36-volt NiMH battery pack located beneath the cargo floor. This battery module is a compact rectangular unit that appears to be about one metre across and about 15 cm by 15 cm in size. It bolts to the body and incorporates a small cooling fan and an automatic battery disconnect that protects the vehicle, and those in or near it if incorrect operation of the system is detected. At 36 volts, the voltages are much lower than the 250 to 300 volts or higher found on other hybrids.
The hardware is the easy part. It is the controller’s software that really brings out the potential of a hybrid. The Vue’s hybrid controller is mounted to the radiator support in the engine compartment and has hoses going to it to circulate coolant through the module to absorb internal heat. The controller controls when the generator/motor unit will operate and how much power it will produce. For example, when sitting at a stop light, the gasoline engine is turned off in “Auto Stop” mode but when driver steps on the gas to pull away, the controller operates the electric motor to start the gas engine. Driving down the road, the electric motor can be used to help the gasoline engine as loads increase. It all occurs seamlessly.
Gauges and indicator lights on the dash tell the driver how the system is operating. A gauge on the right of the dash display shows whether the system is charging the battery pack or assisting the gasoline engine. An “Auto” light in the tachometer comes on when the engine is in the “auto stop” mode at stoplights so the driver remembers the vehicle is still operating. Electric power steering enables steering when the gas engine is stopped and an electric pump inside the automatic transmission keeps the transmission engaged in gear.
Compared to other hybrids on the market, the BAS system looks extremely simple. It doesn’t provide as much power or regenerative braking as other systems but does improve fuel economy and requires little to incorporate on the vehicle. Priced at $28,795, the $2,600 additional cost for the Vue Greenline hybrid can quickly be paid back in fuel savings. The simplicity of the BAS system makes it a more economical system to build and for us to buy.