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Chevy Volt Delivers Novel Two-Motor, Four-Mode Extended Range Electric Drive System; Seamless Driver Experience Plus Efficiency

by Mike Millikin and Jack Rosebro

Voltkinematics
The Volt drive unit combines two motors and three clutches to deliver four distinct operating modes to maximize efficiency and provide a seamless driving experience. Click to enlarge.

During the serial media launch events for the Chevrolet Volt, GM provided more detail (subsequent to the completion of related patent work) on the novel drive architecture applied in their first extended range electric vehicle to enhance the efficiency of both the battery electric and extended-range driving modes.

The complex system leverages GM’s learnings from its two-mode hybrid system in a number of areas, including the efficiency benefits of a multiple-motor approach to meeting the full range of electric drive operating requirements; synchronous clutches; and the vehicle’s control software and architecture.

The Volt is an electric-drive vehicle, powered by a 16 kWh Li-ion battery, incorporating an internal combustion engine and generator to serve as a range extender; an electrical plug is intended to be the primary source of stored energy used to deliver motive power. (The Volt could also be called a plug-in series hybrid, depending upon your taxonomic preference.)

Given that GM had committed to a combustion engine and a generator as a range extender for the battery, the engineering team set out to develop a drive system that could maximize the combined efficiency of all the components under the different driving modes (all battery electric, and extended range). Put another way, the GM team wanted to extend the range of the vehicle as efficiently as possible, while maintaining quality driving dynamics and experience.

The story of the electric drive is really a story about efficiency. How do we take all this battery energy...and very efficiently and effectively drive the wheels. That’s ultimately what the customer is looking for, is to maximize this notion of electric range, to maximize this notion of efficiency of the generator when we have to use it.

—Pam Fletcher, Global Chief Engineer for Volt and Plug-In Hybrid Electric Powertrains

Mechanical losses such as friction and windage dictate that the efficiency of an electric motor declines somewhat as motor speed increases. Recognizing the benefits derived from their two-mode approach in their earlier hybrids, the engineering team also observed that they had a second motor—the generator motor—“going along for the ride”, as Fletcher said during her presentation at the launch event in Detroit. They thus decided to exploit the generator motor more thoroughly than it would otherwise have been if used exclusively as a generator in extended-range driving.

The resulting Volt drive unit consists of two motors—a 111 kW main traction and 63 kW (at 4800 rpm) generator motor (55 kW generator output)—as well as three clutches and a planetary gear set tucked in the end of the traction motor that improve overall efficiency by reducing the combined rotational speed of the electric motors as needed.

This engine obviously has the capability of revving much higher and producing much more output. But this is really a study in rightsizing, rightsizing an internal combustion engine for this extended range capability. We’re almost repurposing an internal combustion engine to provide this very unique type of propulsion. That’s how much power output we determined we needed for this car that has a very large battery and almost a half-size engine in terms of displacement to provide you with the average power required to provide an urban and highway type commute.

—Pam Fletcher

This configuration reduces battery drain at steady state, cruising speeds in a window ranging from around 30 mph to more than 70 mph (48 to 113 km/h), adding up to two miles (3.2 km) of additional all-electric range. The Volt delivers a pure-electric range between 25 and 50 miles (40 and 80 km)—depending on terrain, driving techniques, driver comfort requirements (e.g., HVAC), and weather. The range extender pushes that to approximately 350 miles (563 km).

The Volt’s drive unit uses an on-axis configuration; motors and gear-set are mounted in an in-line with the range-extending internal combustion engine. Two of the clutches are used to either lock the ring gear of the planetary gear-set or connect it to the generator/motor depending on the mode. The third clutch connects the internal combustion engine to the generator/motor to provide range extension capability.

The 111 kW traction motor is permanently connected to the sun gear, and the final drive (gear reduction, differential) is permanently connected to the planetary carriers. The planetary carrier gears are used to modulate gearing ratios between the vehicle’s electric motors, its internal-combustion engine, and its 2:16 final drive.

The Volt has two primary driving modes:

  • All battery-electric (charge depleting), in which the battery is the sole source of power for the motors; and
  • Extended-range (charge sustaining), in which the battery and engine work together in different operating modes to power the traction motor and to improve overall efficiency.

Each of these two driving modes is supported by two drive unit operating modes: a low-speed, 1-motor mode, and a high-speed, 2-motor mode.

Mode1
Mode 1. Click to enlarge.

Mode 1: Low-speed EV Propulsion (Engine Off). In this mode, the ring gear is held (locked) by clutch C1. With clutch C2 and C3 disengaged, the generator-motor is decoupled from the engine as well as the planetary gearset. As the traction motor is permanently coupled to the sun gear, the planetary carriers must rotate when the traction motor rotates. Since the planetary carriers are permanently coupled to the final drive, the traction motor propels the vehicle. The generator-motor and the engine are idle during this mode, although the engine is free to start if necessary (example: engine maintenance mode).

Virtually all of the vehicle’s motive power is therefore delivered by the traction motor in this mode, including hard accelerations, using power supplied by the battery pack. With this configuration, the traction motor can produce up to 111 kW (149 hp) and deliver up to 370 N·m (273 ft-lb) of torque.

Mode2
Mode 2. Click to enlarge.

Mode 2: High-Speed EV Propulsion (Engine Off). As vehicle speed increases, motor speed and losses also increase. To engage both motors and preserve motor efficiency, clutch C1 is disengaged, allowing the ring gear to rotate. At the same time, clutch C2 is engaged, connecting the ring gear to the generator-motor. The generator-motor is then fed current from the inverter, and runs as a motor. The engine remains disengaged from the generator-motor.

This mode allows the two electric machines to operate in tandem at a lower speed than if the traction motor alone was providing torque. The speed of the traction motor in this mode drops to about 3250 rpm from 6500 rpm in the 1 motor mode, according to Fletcher.

This strategy allows the Volt to wring out as much as two extra miles of all-electric operation out of its battery pack, depending on operating conditions. However, switching from low-speed to high-speed EV mode requires the simultaneous operation of two clutches. GM’s experience with simultaneous clutch operation in their two-mode transmissions and transaxles was key to the development of the Volt’s transaxle control strategy.

Mode 3
Mode 3. Click to enlarge.

Mode 3: Low-speed Extended-Range Propulsion (Engine Running). Once the Volt’s battery pack has reached its minimum state of charge (SOC) (which varies depending on operating conditions), clutch C1 engages, locking the ring gear, and clutch C2 disengages, decoupling the generator-motor from the ring gear. At the same time, clutch C3 engages to couple the Volt’s 1.4 liter Ecotec range-extending engine to the generator-motor, so that it may be operated in generator mode.

During low speeds as well as hard accelerations, the traction motor propels the vehicle. The engine drives the generator-motor, and power to drive the traction motor is delivered by the generator-motor as well as the battery pack via the Volt’s inverter. Under most conditions, the generator will provide enough power to maintain minimum battery SOC, and therefore allow the vehicle to remain in this mode until it is plugged in.

Mode4
Mode 4. Click to enlarge.

Mode 4. High-Speed Extended-Range Propulsion (Engine Running). The blended two-motor electric propulsion strategy used at higher speeds in EV driving has also been adapted for extended-range driving. In this mode, the clutches that connect the generator/motor to both the engine and the ring gear are engaged, combining the engine and both motors to drive the Volt via the planetary gear set. All of the propulsion energy is seamlessly blended by the planetary gear set and sent to the final drive.

This novel mode—which GM calls “combined mode”—enables a 10-15% improvement in efficiency at steady state cruising speeds compared to a comparable single-motor mode, GM says. Under no circumstance can the Volt be propelled by engine torque alone; the traction motor must be operating if the vehicle is to move and the engine is to provide torque.

When we’re in this combination...on this planetary gearset we are driving the engine-generator combination onto the ring gear. We are utilizing the traction motor to provide the reactionary force so that we can ultimately drive the output. That is what happens in combined mode, that’s what allows us to get the 10-15% more efficiency.

—Pam Fletcher

In this mode, the generator still continues to produce electricity as well as deliver torque via the gearset, Fletcher said. The ratio of torque to power generation varies with operating conditions, and is, as the rest of the system, under the management of the control software, according to her. As noted earlier, the control software and architecture enabling this drive unit is critical to its overall success. We anticipate that additional information will be disclosed about the control mechanisms for Mode 4 as patents are awarded and SAE papers are approved for publication.

Packaging of the drive unit. The drive unit is quite compact, and includes the power electronics as well as the engine, motor generator, planetary gearset and traction motor. The power electronics unit includes three IGBT inverters: one for each motor, and one for the electric oil pump.

“If the Volt is in electric mode, we can accelerate the car wide open throttle to 100 mph—so you can have the full performance envelope of the car all electrically. That to me is a very important point.”
—Pam Fletcher

Driver experience. During the launch event (which GCC attended courtesy of GM), journalists paired off to drive pre-customer versions of the Volt on roads under different conditions for almost 200 miles. Based on that limited sampling, we can report that the transitions between modes are seamless and smooth; at one point, we had entered into range-extending mode without even knowing. The Volt accelerates crisply (and quietly), and handles snappily at moderately excessive interstate speeds—all on battery power.

The sole exception to the noise quality was on entering into mountain mode (driver-selected via the console); the engine races loudly.

The Volt offers three driver-selected modes: normal, sport, and mountain; mountain mode is designed to help the Volt traverse particularly steep and long grades—e.g., the Eisenhower Pass. This mode increases minimum battery SOC to around 45%. The driver will hear more engine noise during mountain mode, due to the higher rate of power generation required to maintain this mode. GM expects mountain mode to be required only under unusual power demand conditions.

GM engineers said that in the customer models, they are implementing a software fix to reduce the mountain mode noise somewhat. That said, GM wants the use of mountain mode to be exceptional—i.e., it doesn’t want customers running on mountain mode to recharge the pack. Power should come from the plug.

Comments

Engineer-Poet

I think the UAW angle may be it. Fiat's Twinair 2-cylinder would have more than enough power (73 kW?) for the Volt, but have a much smaller parts count and assembly labor. The Volt sustainer's specific power, ~38 kW/l, is also about half of the Twinair. There's no reason to de-rate an engine that's only used a small part of the time without getting some other advantage (an Atkinson camshaft and higher-compression pistons would increase efficiency... which was not done) so it is probably being done on the cheap engineering-wise and throwing a sop to the union.

Quoth Jason:

charging a vehicle from electricity in the grid in the United States is far from green. With a loose classification on what is considered a renewable energy source, very few states or metropolitan areas currently have above a 10% energy consumption rate from renewable sources.
But there are substantial advantages. The future Smart Grid works well with PEVs and makes room for wind and nuclear. Even before that, energy diversity goes up because coal and natural gas are substituted for imported oil.

Roger: Electric propulsion pulls the heaviest wheeled loads on the planet (diesel-electric trains). Going Atkinson (or Miller cycle, with a TIGERS to capture the remaining energy in the exhaust) would increase efficiency more than the mechanical torque path, while simplifying and lightening the car.

HarveyD

Electrified cars overall performance is (not all) but very total weight relevant. Why lug around 300 lbs to 500 lbs genset if a 100 lbs unit could do it?

Since the typical PHEV user will be using electricity accumulated into the on-board batteries 80+% of the time, the efficiency of the very light weight genset may not have to be the highest available.

Customers/users could have the choice between heavier more fuel efficient genset and light unit that may no be as fuel efficient to favor overall efficiency and to reduce battery size and initial cost.

Roger Pham

I sure hope that the UAW angle is not it, since those in charge should have realized that making a product that is more complex and expensive than needed to be will not sell well and will hurt employment and wages.

Talking about cheaper and lighter, let's consider an alternate PHEV design, a serial-parallel hybrid with same payload rating as the Volt, starting with a 55 kW motor#1, a 35 kW engine and a 30 kW generator/motor#2. There will be also two clutches and a simple two-speed transmission connected to the differential unit. Clutch 1 connects the engine to the generator/motor2, and clutch 2 connects the generator/motor2 to the traction motor 1. When the engine, generator/motor2 and motor 1 are all clutched to the differential, the combination will add another 65 kW of power to the 55kW motor, for a combined total power rating of 120 kW. Interestingly, the sum total of installed generator/motor power is only 85 kW, vs. 170 kW for the Volt. The installed engine power is only 35 kW, vs 50 kW for the Volt. This 35 kW should be good for 80-90 mph top speed on engine power alone. However, the combined 120 kW of power should allow >120 mph top speed until the battery is out of juice.

How can 1/2 the installed power of this PHEV design equal to the Volt's 0-60 mph acceleration? This is because from 0-60 mph, the two speed transmission is in low gear at 2:1 ratio, hence it doubles the torque of every power plants in this PHEV and allows maximum hp output at 60 mph, whereas in the Volt's planetary CVT the combination of power from all the power plants at the same time can only drive the vehicle at 1:1 ratio, due to its design. After 60 mph, the transmission is forced to shift to high gear, to 1:1 ratio, but at this speed range, optimal torque from all the power plants will be obtained, so acceleration will also be very good, though not as good as the Volt's acceleration from 60-120 mph...but, in consideration of the speed limits at 60-70 mph in most places, it is inappropriate to equip a high-efficiency vehicle to encourage cruising at speeds that will lead to waste of fuel and and much higher risks of traffic fatalities.

Now, then, ask ourselves, why do we need 16 kWh of battery capacity, when 8 kWh of battery will do just fine, allowing seating capacity of 5 instead of 4 as in the Volt, and shaving ~200 lbs of weight and ~$4000-5000 USD off the retail price?
The reduction in installed motor/generator/power inverters/cooling accessories/engine capacity should shave another 300-400 lbs off the curb weight. The vehicle's tire, wheel, suspension, chassis can also be enlightened as well, shaving off another ~200 lbs of weight. I can see a total saving of ~700 lbs of weight in this lighter serial-parallel PHEV version, and at least $10,000 USD off the retail price.

Because the new vehicle will be much lighter, it will easily do 25-27 miles in all EV mode out of the 8kWh battery pack. If your commute is >20 miles each way, then all the owners of this reduced-range PHEV can use this excuse to ask for a reserved parking spot right next to the building, essentially a VIP spot, while laughing all the way to the bank depositing the ~$10,000 USD that you've just saved. Owners of the Volt, with 40 mi all EV range, will likely be denied the coveted charging lot at work if they live less than 20 miles from their work place!

What about all Electric performance of our lighter serial-parallel PHEV? It has a two-speed transmission to double the gen/motor 2 and motor 1's torques from 0 to 60 mph, at 2:1 reduction ratio, in order to match the Volts' twice-as-much installed power but at 1:1 drive ratio. This will provide it with superior acceleration over that of the Volt, up to 60 mph, due to its 700-lb lighter weight. Combined power of both the gen/motor 2 and traction motor 1 will be 85 kW. This will allow it to keep up with most conventional ICE vehicles in the road today.

Jason

@ Engineer-Poet

I'm confused at what you are arguing. If you are concerned with our reliance on foreign oil, then electric vehicles only worsen our dependence. Right now China produces around 97% of the total rare earth metals with the remaining coming from some countries in the Middle East and South America.

Even if petroleum is substituted with coal and natural gas, they will still produce harmful emissions.

How does "the future Smart Grid work well with PEVs and make room for wind and nuclear"? The last I checked, the United States transmission infrastructure was in dire need of repairs let alone upgrades. To give you an example the transmission infrastructure in the US is twice as inefficient as it was in the 1970's. How are we going to pay to install miles and miles of new transmission lines to utilize wind turbines if we can't keep what we have now in decent shape?

ejj

The Volt is also going to be full of all kinds of bells and whistles on the inside which will be standard. In other words, you have no choice but to buy all the extra advanced "premium" audio/visual features, and power windows, seats, etc. I've read this is a Toyota trick to squeeze more profit out of the Prius...GM will get away with it initially but over time markets will develop for a stripped down version of the Volt or some other model with the voltec powertrain. All the extra features that you will be forced to buy if you want a Volt mean jobs, jobs, jobs...many of them UAW.

Reel$$

"Any possible way to increase the complexity and dependency of the Volt on the ICE will mean more UAW jobs and job security."

This may have been the case with old GM. New GM is well aware that old tricks like over-engineering and planned obsolescence will not fly. Too much scrutiny. UAW will lose dominion in some cases to IBEW - since EVs will have many more electrical components than mechanical.

If either UAW or IBEW represent the best interests of their members, they will negotiate equity for employees.

"Those Volt skeptics out there are going to be badly embarrassed if they keep doubting the seriousness of this vehicle.” -- Motor Trend

Reel$$

Here is Motor Trend's comparison of Plug-Prius to Volt:

http://www.motortrend.com/roadtests/alternative/1010_2011_chevrolet_volt_test/engine_graphs.html

Engineer-Poet
If you are concerned with our reliance on foreign oil, then electric vehicles only worsen our dependence. Right now China produces around 97% of the total rare earth metals...
The EV-1 used twin induction motors, no rare-earths involved.
Even if petroleum is substituted with coal and natural gas, they will still produce harmful emissions.
True, but (a) generally less (the Volt running on electricity from NG is much better than the Volt burning gasoline, and even coal is close to a wash), (b) we can not only substitute over time, the increased fraction of schedulable load makes substitution more attractive, and (c) almost no NG and no coal are imported from hostile countries.
The last I checked, the United States transmission infrastructure was in dire need of repairs let alone upgrades.
Replacing $3/gallon gasoline with $0.75/gallon-equivalent electricity will give us enough savings to fix the grid. Just moving demand from afternoon peak hours to the dead of night will squeeze more out of the existing system without stressing it.
kelly

Comments often state that EV's only move the exhaust pipe to the US grid's 50% coal power plants.

Roughly, as I understand:

1. A coal plant is twice as energy efficient as ICE (40% vs 20%) producing electricity.

2. A EV drive is over four times more efficient with the energy it gets (80+% vs 20%).

In any case, electric drive would be several times more energy efficient and less polluting. Plus, the future will likely see more renewable electric sources besides the cleaning of CO2/smoke stack emissions.

Is this incorrect?

clett

I think there are two incredible things about this car that the press really hasn't appreciated.

1) It's a car weighing 1,720 kg that can still do 4 - 5 miles per kWh.

2) Journalists are averaging 35 - 38 mpg (US) in charge sustaining mode.

Number 1 is incredible, as those miles per kWh numbers are what we would expect from a 1,200 kg EV.

Number 2 is also remarkable as the Volt is making do with a low-efficiency Otto cycle engine. If it had a 36% efficient Atkinson cycle engine (as in the Prius), it would likely manage 42-45 mpg. This is exceptional for a car weighing 1,720 kg and a clear endorsement of the efficiency of the series-hybrid set up even at highway speeds.

Engineer-Poet

Coal-fired powerplants in the US average about 33% efficient (10200 BTU/kWh heat rate). The Wabash River IGCC plant pushes 40% (it gets a full 40% running on petcoke) and ultrasupercritical steam plants supposedly will hit 45%.

Gas-fired CCGTs hit 60%, and NG has half the carbon/BTU of coal.

richard schumacher

We certainly wish them well, but it looks too complicated and expensive for the benefits it delivers. A plug-in series hybrid using an HSD driven by two motor/generators (for low-speed torque) with no direct connection to the engine would likely do as well and cost less. GM surely studied that and several other drive trains; it would be nice to know the real reasons for their choice.

danm

Must agree with those who are disappointed by the complexity, but doubt the UAW/dealership influence. More likely GM still clinging to the old model of "I gotta have a tank of gas".
Still yearning for that simple, cheap EV...

HarveyD

A scaled down series type locomotive could do just a well. Too bad that GM did not use the ultra light EV-1 design.

Less complex Series hybrids (PHEVs) will have better overall performance when batteries have better (2x +) energy density and when coupled with ultra light gensets. That's what many manufacturers will offer by 2015/2016.

India and China may be the first to produce basic common sense lighter series PHEVs. Of course, we will do our best to block their importation.

danm

Ugh. This is ugly. I guess the ME's still hold sway of GM.

TXGeologist

GM left out the most important clutch and they did it on purpose, Clutch 4 should be on the sun gear to release the Motor1 and lock the sun gear fixed therefore allowing the ICE and the MG/2 to drive the ring gear which though the planets drive the planet carrier and the final output to the wheels solely. This would increase hwy efficiency even more as with the current setup energy (torque) has to be sent electrically from MG2 to M1 continuously at hwy speed.

This is to keep the Ecvt concept and have this car qualify as an EV, had GM allowed the ICE to solely drive the wheels even at hwy speeds this would not be an EV and no subsidy cashcow from the feds. I would be a simple matter of engineering to add clutch on the sun gear and make sure the final drive ratio is optimized for the ICE minimum BSFC at hwy speeds say 75mph which is about the average people drive unless your in far West TX where the speed limits are 80 and people drive 90-100 mph anyway. MG2 is still in the torque path to the wheels which allows for charging of the pack and torque boost and regen braking while at hwy speeds. Using the MG2 to charge the pack can also keep the ICE at its most eff point which for most ICE is 75% max torque at WOT, they should have used multiair for the throttling of this engine or some other valvetronic means this improves hwy mileage significantly. Which is where the ICE should be doing its heavy lifting.

TXGeologist

As for complexity a modern 6 speed automatic trans has at least 3 some times 4 epicyclic gear sets and each gear set has 3 to 4 wet clutches/ band clutches for a total of 12 or more wet clutches in a normal automatic trans, these trans drive millions of cars today without issue, I personally have had truck/ SUV auto trans that have gone over 200k miles on the original clutch packs, the key is regular fluid replacement and using a oversized trans fluid cooler heat is death to trans fluids, and the wet clutches the fluid supports. The gear set last almost indefinitely when you rebuild an automated trans your replace the clutch packs and band clutches and put the original epicyclic gears back I have done a few tranny rebuilds in my day anyone with a high school shop level education can do it. GM’s single epi gear set is childs play for them given the decades of experience doing automated transaxles the trick is synchronizing the clutches and that what computers do best keep the user out of the equation and computers can sync gears to <10rpm relative speed differences there should be little to no wear rates on the clutches if the computers do the job of the syncros.

Stan Peterson

All the Toyota fans and the media, like Jalopnik, are accusing GM of prevarication. What utter drivel.

The only time that the mechanical connection is engaged is when you are exceeding most, if not all the speed limits existing in the USA. I concede some western Interstate speed limits exceed 72 mph, but not many.

If GM speed-limited its Volt to 70 mph or even 75mph, it would never have needed this mixed mode. You have to be traveling in excess of 72 mph, and not on flat ground, with the battery at minimum SOC, to have this parallel and series, mixed mechanical mode engage.

All other times the Volt is as advertised, a series EV with extended range. The overall gasoline fuel economy on any lengthy time measure like a month to a year will produce a gasoline consumption exceeding 230 mpg.

That is 5 times the best gasoline consumption produced by a Prius or Fusion. GM has learned the hard way that politicians and bureaucrats are not to be trusted. GM measured the gasoline consumption using the EPA's draft and planned standard and then the bureaucrats wavered and double-crossed them.

Now they won't issue a gasoline fuel economy measure until the dumb bureaucrats have to get off their collective asses, and make a decision; and adopt a firm procedure for such measurements. When they did so before, with the draft J1711, the produced result was 230 mpg.

The secret is that the electrical miles consumed are always consumed first,before a drop of gasoline is consumed. That makes all the difference since the average US driver travels less than 40 miles/day between expected charges. That is the way that a Volt substitutes electricity, and therefore consumes less than 10% of the gasoline of a conventional car.

Or conversely, the implication is that a US auto fleet based on EREV designs would reduce gasoline consumption to 1/5 of today's consumption pattern, eliminating oil imports and wrecking OPEC. If the USA went forward with synthetic fuels, to raise the percentage from about 15% to 20%, we would need no fossil fuel Oil, at all. So much for the Blarney from the Peakist Cassandras.

For the design purists here, a simple two-speed transmission for the traction motor, or alternatively, just accepting the minor inefficiency, in lieu of the mechnical connection, would have worked as well.

Roger Pham

Thanks, TX and Stan, for your input.

Agree that the Volt indeed is GM's ambitious show case of what performance level can be achieved even with the highest of efficiency. GM spared no expenses nor engineering labor to ensure that only the best of technologies are employed here. The total max hp output of the Volt is almost 300 hp, quite befitting of luxury-level marks like Cadillac, BMW, MB, Lexus, etc...
As such, GM ought to compare the Volt to more expensive luxury-brand. The $41,000 price is very inexpensive with respect to its performance level, further sweetened by the $7,500 tax incentive, and by the saving in fuel costs, to the tune of $10,000 USD.

May be rebadge the Volt as a Cadillac, and rename it the Cadillac Electra, or something sexy!!!, or Super Electroglide...(no attempt to appease to Harley aficinados). I will volunteer to help sell the Volt against expensive imports, if GM so desires.

Reel$$

Roger, you help everyone not just GM if you support the transition to electrification. The Volt, Tesla, Leaf and Prius may not be the best B/HEVs - but they are at least a start. And we all should get behind these car makers to tout the different offerings just to get the EV industry under way.

I just drove the Tesla Roadster again. It is truly amazing to drive a pure EV. When I passed the big Texaco station on my beach drive - it really sank in. The car I am driving gets it's fuel at home. No need to EVER stop in for a gasoline fix again. Wow. Petroleum recovery!!

Roger, I am sure GM would be happy for your support.

Engineer-Poet

Stan, the average fuel economy of the US LDV fleet is closer to 25 MPG today; going to 230 MPG would cut gasoline consumption from about 9 mmbbl/d to around 1.

The USA still pumps around 5 mmbbl/day of crude. If the rest of the economy could achieve similar savings, oil imports could be eliminated.

HarveyD

How many years will it take to replace 240 million ICE vehicles with 240 Million HEVs/PHEVs/BEVs?. The first million took 13 years. The transition rate will have to be accelerated many times, otherwise it may take 240 years.

Our love affair with large gas guzzlers runs very deep. It took almost 50 years to go from horses and buggies to ICE vehicles and it may take as long to go to electrified vehicles unless pro-active governments programs are used.

Engineer-Poet

How many years did it take for the USA to have "Victory Gardens" almost everywhere? A big enough shock to the system can change the societal ethos overnight.

Putting up manufacturing and assembly plants takes more time, especially for specialized items like batteries. Still, if we moderated our demand during a changeover (very few large vehicles) and built almost nothing but plug-ins afterward, we'd eliminate half of oil consumption in roughly the time it takes for vehicles to run half of their lifetime mileage. That's only about 6 years at current usage patterns, so I can see a serious push slashing gasoline use to ~4 million bbl/day by the early 2020's.

cujet

There is an awful lot of GM and, in particular, Volt hate in the press and on the internet right now. I'll admit I got caught up in it too.

However, I reviewed the battery size, at 16,000 watt/hour, that's a lot of power. That's roughly equivelent to 50ea, 12v 40AH 40 pound lead acid batteries when depth of discharge is factored in. In other words, this thing has the power of maybe 2000 pounds of lead acids. It really is electric, and the batteries can do useful work.

For my commute, at 26 miles, plugging in at work too, it would work perfectly. With very little gas use. Now to make a sports car version that I would actually enjoy.

Bottom line, GM did not come clean, but so what? I like it.

HarveyD

E-P: I wish that it could be done that fast. If batteries energy density could be multiplied by at least 2x by 2016 (to 400+ Wh/Kg) and their price cut in half (to less than $400 KWh), PHEVs/BEVs sales could take off.

However, 2011-2015 electrified vehicles sales we likely be slow due to low batteries performance and their high price. A breakthrough on batteries and/or ultra-caps would really help.

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