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Hybrid Vehicles Chevrolet Volt Will the Chevy Volt Succeed?
544 messages, Last post on Oct 28, 2009 at 1:11 PM
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Replying to: eaton53 (Sep 24, 2008 1:49 pm) Well the objective should be to use our tax dollars to promote a maximum displacement of gas usage. Encouraging people to buy vehicles that use no gas does not necessarily accomplish this if the vehicle sees reduced service due to it's limitations. |
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Replying to: eaton53 (Sep 24, 2008 3:06 am) This would require a transmission similar to the HSD. I have not heard that the Volt will have regen braking. From what I have read the transmission is pure electric, without the reverse-generator function of the HSD that puts charge back in the batteries. |
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Replying to: tpe (Sep 24, 2008 5:28 am) That is what GM said; "a gasoline/E85-powered engine generator seamlessly provides electricity to power the Volt's electric drive unit..." Energy does not go to the battery; it simply stays at whatever SOC it has when "depleted". I read that statement to mean that the ICE powers the electric motors, no batteries involved. I suspect that the Volt does not have ANY on-board capability to recharge the batteries, including regen braking. |
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Replying to: stevedebi (Sep 24, 2008 3:47 pm) The system seems the same as the production systems found now: ” When the brake pedal is applied (foot comes off accelerator pedal) the Electric Traction motor switches to a “Generator”. http://gm-volt.com/2007/02/28/volt-has-regenerative-braking/ |
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Replying to: stevedebi (Sep 24, 2008 3:47 pm) It makes sense if you consider energy efficiency and energy loss on conversion from one point to another. For example, if mechanical energy converted to electrical energy is optimistically 90% efficiency (ICE to generator), and the electrical energy converted back to mechanical energy at the axle at 90% efficiency (via electric motor), the resulting transmission efficiency from ICE to the wheel of volt would be about 81%. A regular automatic transmission can do better than that. But, of course, in an automatic transmission, the engine does not shut off when the car is stationary. Now if the electricity generated passes by the battery before it is released to the electric motor, there is additional efficiency loss due to energy conversion from electrical energy to chemical energy and back. And that is by a factor of roughly 50-60%. If the generator-motor would have 81% transmission efficiency, the generator-battery-motor would have 48% transmission efficiency. That is actually a horrible figure. However, the volt is designed to be powered by batteries that is primarily charged by grid electricity and not by the ICE and that is where it make it's economic rationale. I would guess that driving the volt with the ICE and with empty battery would be a terrible waste of fuel especially on the highway. Much worse than a regular car. |
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Replying to: peralta (Sep 24, 2008 7:26 pm) |
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Replying to: peralta (Sep 24, 2008 7:26 pm) How Does It Work? The Chevy Volt will use a new powertrain that GM is referring to as the "E-Flex" system. It uses electricity to move the car at all times, and uses an engine as a generator to repenish its batteries. To charge it, owners will plug it into a standard household electrical outlet. When they drive the car, it will use only its electric motor, no matter what speed it is driven, until its battery has less than 30 percent of a full charge remaining. At that point, a small four-cylinder engine will turn on. That engine will not directly send power to the wheels -- instead, it will act as a generator, recharging the batteries. According to GM Vice Chairman Bob Lutz, the Volt will use its GPS system to determine how long to run that engine. "The car will know how far you are from home," Lutz told reporters in September, "and it will only run the gas engine long enough to give you enough charge to get you home where you can actually plug it into the wall outlet. So the car will be smart enough to know where its home base is." GM engineers estimate that the average driver will be able to travel 40 miles before the gasoline engine even ignites. But the range of the Volt under battery power alone will change based on how much weight it is carrying, how fast it is traveling, and other factors. The 40-mile figure is significant, however, because most Americans drive less than 40 miles per day. For many owners, the Volt would function as an electric car virtually all the time, using gasoline only when they took longer trips than they take on a typical day http://usnews.rankingsandreviews.com/cars-trucks/2010-Chevrolet-Volt/ |
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Replying to: peralta (Sep 24, 2008 7:26 pm) One is for the regular 40 mile or less per day usage before recharging, second is for Max fuel economy mode with up front display of range before battery is depleted, for travels > 40 miles and third is for Max battery range with same up front display of range before battery is depleted, for indefinite all day long travel. OR You have the option to enter data into the car on how many miles you plan to travel for the day then the car will automatically calculate for best usage of power between battery and ICE. OR better You enter your intended travel for the day in the car's navigation and the car calaculates for itself the total distance to be travelled. If you ran out of battery prematurely, you will be driving inefficiently on ICE while dragging along the heavy dead batteries. The ICE is most efficient if the car is already in motion since it doesn't have to inefficiently channel energy through the batteries. The ICE would even be more efficient with almost 100% transmission efficiency if there is a clutch for direct mechanical drive, ideal for indefinite highway driving.
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Replying to: peralta (Sep 24, 2008 7:26 pm) They're saying 50mpg. If it hits that number it will be much better than a regular car. There is also talk of using On-Star so your Volt will always know how far it is away from home and attempt to to optimize its operation. I have a 19.2 mile each way commute... a nearly ideal Volt distance. I'm sure the engine would run occasionally, which is not necessarily a bad thing. It keeps things lubed and the gas fresh. Volts should have a program that runs them occasionally for that reason, even if you never exceed battery range. I'd think people considering Volts would ask themselves how often they would go over 40 miles without having charge access. For something like 80% of the population the answer would be "not often". |
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Replying to: peralta (Sep 24, 2008 9:58 pm) That would be the most efficient way to use the ICE but I think it would add complexity, weight and cost. The ICE is not going to be powerful enough to be the sole source of propulsion in some driving conditions, eg accelerating, going up a grade. So you'd need the capability of being able to supplement the ICE with the electric motor. I think your previous suggestion where the ICE generator directly powers the electric motor and uses it's occasional surplus to keep the batteries at 30% SOC has a lot of merit and it doesn't sound like a monumental engineering feat to accomplish this. Who knows, maybe the Volt will be doing this to some extent. In addition to it's greater efficiency it would reduce charge cycles on the battery pack. However you'd still want to only operate the ICE in a narrow power range that represented it's peak efficiency.
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