The system can provide the equivalent power of about 15 horsepower and 79 lb-ft of torque. When you brake, you actually tell the generator to put some load on the engine, which slows the car, and allows the generator to make and send lots of juice. Conventional brakes work in concert with this regenerative braking system.
Auto-Stop and Transmission Technology
The IC engine shuts off whenever the car stops in traffic and/or at intersections. The motor-generator restarts the car by turning the crankshaft. Wilson noted that GM was able to refine the auto-stop function by adding an auxiliary electric-driven transmission oil pump, which keeps the transmission primed and fluid flowing.
This allows the vehicle to accelerate smoothly as soon as the IC starts up—no waiting for transmission pressure to build up after an engine shutdown. The motor-generator also makes sure the engine is stopped in the perfect position for a smooth restart.
Buick engineers also noted that, unlike other mild hybrid systems, which tend to funnel electrical power through the flywheel, which necessitates a specially designed torque convertor, eAssist uses a completely conventional torque converter.
To further fuel efficiency, the eAssist system keeps the torque convertor “locked” almost all of the time. It is able to do this because eAssist can blend in electric power at opportune times, to smooth some torque transitions that would otherwise have to be accomplished through the torque converter.
The ability to blend in electric power at opportune circumstances also allows the transmission to stay in its gear more often—so there is less downshifting and revving. It also enabled the LaCrosse eAssist to use a lower final-drive ration (2.64:1 vs 3.23:1 in the regular four-cylinder LaCrosse).
Battery Pack
In the trunk, you’ll find a module containing the 115V 32-cell lithium-ion battery pack, an integrated power inverter and its 12V power supply, a controller, and an electric cooling fan. The cooling fan draws air from a vent in the package tray behind the rear seat. The unit looks like a long, narrow suitcase, and weighs about 65 lbs (29 kg). Trunk space is obviously reduced a bit. There is still a useful trunk pass-through, though the module fills up some of the opening.
The 115V lithium-ion battery powers all of the Buick’s electric functions, whether the IC is running or not. The only time the “regular” battery is used is to spin the starter, when you first get into the car for your drive.
Wilson noted that Hitachi provided the battery pack and the controller, and that the module assembled at a GM facility. They went with Hitachi, said Wilson, because this battery’s dynamics suits the eAssist mandate: “This battery is optimized for power… We take power out, and put power in, very quickly and constantly. The Volt battery, on the other hand, is optimized for energy storage and power”.
Auto-Stop and Transmission Technology
The IC engine shuts off whenever the car stops in traffic and/or at intersections. The motor-generator restarts the car by turning the crankshaft. Wilson noted that GM was able to refine the auto-stop function by adding an auxiliary electric-driven transmission oil pump, which keeps the transmission primed and fluid flowing.
This allows the vehicle to accelerate smoothly as soon as the IC starts up—no waiting for transmission pressure to build up after an engine shutdown. The motor-generator also makes sure the engine is stopped in the perfect position for a smooth restart.
Buick engineers also noted that, unlike other mild hybrid systems, which tend to funnel electrical power through the flywheel, which necessitates a specially designed torque convertor, eAssist uses a completely conventional torque converter.
To further fuel efficiency, the eAssist system keeps the torque convertor “locked” almost all of the time. It is able to do this because eAssist can blend in electric power at opportune times, to smooth some torque transitions that would otherwise have to be accomplished through the torque converter.
The ability to blend in electric power at opportune circumstances also allows the transmission to stay in its gear more often—so there is less downshifting and revving. It also enabled the LaCrosse eAssist to use a lower final-drive ration (2.64:1 vs 3.23:1 in the regular four-cylinder LaCrosse).
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| Photo: Buick |
Battery Pack
In the trunk, you’ll find a module containing the 115V 32-cell lithium-ion battery pack, an integrated power inverter and its 12V power supply, a controller, and an electric cooling fan. The cooling fan draws air from a vent in the package tray behind the rear seat. The unit looks like a long, narrow suitcase, and weighs about 65 lbs (29 kg). Trunk space is obviously reduced a bit. There is still a useful trunk pass-through, though the module fills up some of the opening.
The 115V lithium-ion battery powers all of the Buick’s electric functions, whether the IC is running or not. The only time the “regular” battery is used is to spin the starter, when you first get into the car for your drive.
Wilson noted that Hitachi provided the battery pack and the controller, and that the module assembled at a GM facility. They went with Hitachi, said Wilson, because this battery’s dynamics suits the eAssist mandate: “This battery is optimized for power… We take power out, and put power in, very quickly and constantly. The Volt battery, on the other hand, is optimized for energy storage and power”.