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The Volt: Still not a hybrid... no lie!


Drew Dowdell

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The Volt: Still not a hybrid... no lie!

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October 11, 2010 - Drew Dowdell

This morning the automotive press' inter-tubes went all a flutter over the revelation that the just released Chevrolet Volt has a clutch that can engage the gasoline engine to the generator which could itself be connected to the wheels when the vehicle is running over 70mph and the battery is depleted. This prompted cries of "GM LIED!" and "IT'S JUST A HYBRID!" due to the fact that since near the beginning, GM has been marketing the Volt as an electric vehicle with an onboard range extender and it had no physical connection from engine to wheels.

That got me thinking: What exactly is the definition of a hybrid? Is there a certain percentage of drive time or torque distribution that causes a vehicle to cross the hybrid/non-hybrid threshold?

Nearly all automobiles have been a combination of internal combustion and electric motors since Cadillac installed the first electric start in 1912. Before the days of the clutch interlock, if your car wouldn't start, you could turn the key with the transmission in first and move the vehicle a few feet. It was a good way to burn out your starter, but it could be done in a pinch. So when my dad did that in his '82 F-250 to move it out of traffic's way in a bad situation, did his old Ford magically turn into a hybrid for those few brief seconds? I think not.

In 2008, GM introduce the Chevrolet Malibu Hybrid and Saturn Aura Hybrid. These vehicles were powered by something GM called Belt-Alternator-Starter or BAS. Any explanation you need is right there in the name. It's was basically a heavy duty belt that allowed a heavy duty alternator to supplement the power of the vehicle's 4 cylinder engine. It also allowed start/stop engine operation in city driving, though a traditional engine starter was retained for cold starts. The BAS system added a grand total of 5 horsepower and could only propel the car up to 3mph. Would you call this a hybrid? Despite GM's marketing department, which called it a "mild" hybrid, I don't buy it. Neither did anyone else and the Malibu was reduced to "Fleet Only" status for 2009.

What about the vehicle that is the very definition of the term hybrid? The Toyota Prius is the best selling hybrid on the market... ever. In the Prius' system, power input is split between the electric motors and the gasoline engine depending on throttle input. Under full throttle, you get power from both sources. Power is combined in a device that Toyota calls the Hybrid Synergy Drive, basically a multi directional transmission that can take rotational energy from 3 different inputs (gas engine, electric motor, or wheels) and send it to two other locations (the electric motor for battery regeneration or the wheels for motion) as circumstances demand. The Prius is able to operate in electric only mode, gasoline only mode, and nearly every blend of in between. Would you call this a hybrid? Multiple power sources going in multiple directions... it most certainly is.

So back to the Volt. I spoke with Pam Fletcher, Chief Engineer of Volt Powertrain Development and asked her what her response is to the people who say "The Volt is just a plug in hybrid". She said, "A hybrid can't do what the Volt can do. If you put the Volt's battery in a hybrid it won't change the nature of the way that vehicle drives." If you drive a Prius and press the throttle all the way, you will get a combination of full power from the electric motor and full power from the gasoline motor for maximum acceleration. However, in the Volt with a full charge, you can get the vehicle up to 100 miles an hour and never use a drop of gasoline. As the battery's charge level depletes below a certain level, the gasoline engine will kick in to "follow behind" and replenish the battery.

The main physical motivation for the Volt comes from a 142hp traction motor. An additional 73 hp can be added on from a second motor if the driver applies more than 80% throttle. If the driver applies 100% throttle with a full battery.... the gasoline engine is still sitting on the sidelines doing nothing. At normal driving speeds, the traction motor is more than enough to hustle the Volt around.

One of the benefits of electric motors is awesome low end torque. A well designed electric motor will have it's maximum amount of torque at zero rpm. Thus as an electric motor increases in RPM, it gradually loses it's torque output. At 70 mph, the Volt's traction motor is turning over 6,000 rpm. Volt's engineering team discovered that this wasn't a very energy efficient rpm to operate at. So at speeds above 70 mph, they couple the smaller, second motor, and reduce the rpm of the primary traction motor. This gains the Volt about 1 to 2 miles of electric only range at 70+ mph.

So where does the controversy lie? It's in the arrangement of the electric motors. That smaller motor mentioned above is usually the generator when the Volt is in regeneration mode. Since you're going nowhere if the battery is drained, the gas engine kicks in to recharge the battery, only if you're going over 70mph, the generator is already in use propelling the car. So the gasoline engine assists the secondary motor which is assisting the primary motor. It's this physical connection to what essentially a dual use component that is sending the likes of Edmunds and Jalopnik into a froth, but in reality gives the Volt a 15% increase in efficiency.

Does this dual use component make the Volt a hybrid and not an EV? Well we have to go back to the original question of, "What make a car a hybrid?" The Volt can be operated at any speed and at any level of acceleration without the gasoline so much as twitching. The Prius, even the coming plug in model, can't do this. The Prius can move on any combination of motive power. The Volt's only motive power is electrical. The Prius can be driven without any electrical assist at all. In Volt, if your batteries ain't glowin, you ain't goin.

So is the Volt a hybrid? No, not really. Even after all this fluff it's still an electric vehicle with an onboard generator. Cries of "GM LIED!" and "IT'S JUST A PLUG IN HYBRID!" are just sensationalist automotive tabloid journalism designed to drive traffic to websites.That the gasoline engine can assist the smaller electric motor under certain conditions, doesn't make it any more a hybrid than the burned out starter on my dad's F-250 was.

To GM, I suggest a new term: EV with ICE assist.

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Well written, Boss.

I was surprised at the rancor in the press over this. Who cares?

No it is important because an early loss of battle in perception and it is same old GM losing the war. GM needs to proactively destroy this notion.

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So where does the controversy lie? It's in the arrangement of the electric motors. That smaller motor mentioned above is usually the generator when the Volt is in regeneration mode. Since you're going nowhere if the battery is drained, the gas engine kicks in to recharge the battery, only if you're going over 70mph, the generator is already in use propelling the car. So the gasoline engine assists the secondary motor which is assisting the primary motor. It's this physical connection to what essentially a dual use component that is sending the likes of Edmunds and Jalopnik into a froth, but in reality gives the Volt a 15% increase in efficiency.

OK, this is a bit confusing so let me clarify it a bit...

When battery is above 30% charge (4.8~16 kWh):

  • Gasoline Engine (84hp) --> NOT CONNECTED TO ANYTHING (NOT RUNNING)
  • Generator-Motor (84hp) --> NOT CONNECTED IF BELOW 70 mph; CONNECTED TO ADD POWER IF ABOVE 70mph
  • Main Electric Motor (149hp) --> CONNECTED TO DRIVE WHEELS

When battery is below 30% charge (below 4.8kWh)*:

  • Gasoline Engine (84hp) --> CONNECTED TO GENERATOR-MOTOR (RUNNING)
  • Generator-Motor (84hp) --> GENERATES ELECTRICITY EXCLUSIVELY IF BELOW 70 mph; CONNECTED TO ADD POWER ABOVE 70mph**
  • Main Electric Motor (149hp) --> CONNECTED TO DRIVE WHEELS

* Note: It is important to note that even at 30% charge when the engine kicks in to sustain and replenish the battery, the Volt still has 4.8kWh of battery power remaining. This is MASSIVE. For comparison, the 2010 Prius has a 1.3kWh battery. 4.8kWh is practically the same capacity as the Prius "Plug-in" Hybrid's battery (5.2kWh). Based on materials published to date, the engine will not strive to bring the battery back to 100% charge. Instead, it'll just keep the charge level at or slightly above 30%. This is more than enough to provide bursts of acceleration without the driver feeling the difference. It also keeps car more efficient on gasoline use by not using gasoline to recharge the battery fully, but differing that until the car can be plugged in to the power grid.

** Note: Because the generator motor is connected to add power above 70mph, and the engine is always connected to the generator motor when the battery is low, there exists a situation where both are connected to drive the wheels. This ONLY happens when the battery is low and the car is being driven at over 70mph.

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The 80% to 30% usage is really intriguing. What if after more research GM realizes that the battery can be used optimally from 100% to 0% range?

The opening up of that extra 50% reserve is just a software update away and suddenly you have 80 miles range (50 to 100 miles depending on how you drive - to be politically correct) plus an additional 300 miles on gas.

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Battery will draw deeper into its reserves with more use, to maintain a similar level of range over time.

But after how long? If after 10 years who cares? And that is where research comes into picture. With modern nanotech li-ion batteries it is matter of time that those reserves drawing will be gone.

If it is less than a couple of years then PI-Prius and Leaf are in real trouble because suddenly the economics will tilt.

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But after how long? If after 10 years who cares? And that is where research comes into picture. With modern nanotech li-ion batteries it is matter of time that those reserves drawing will be gone.

If it is less than a couple of years then PI-Prius and Leaf are in real trouble because suddenly the economics will tilt.

I don't know... practically every battery I've seen loses its ability to store energy after many charge and discharge cycles. Perhaps one day, there will be batteries that last forever, but in the meantime, having a reserve makes sense. And anyway the Volt needs a buffer to perform well, since the generator makes less power than the electric motor needs.

I don't see how the Leaf will be in trouble if suddenly batteries last forever. In fact, I think EV cars will be even more compelling. The Prius can easily change to the Volt's design, because they both use planetary gearboxes and two electric motors to create an eCVT; Volt just adds a couple of clutches to completely decouple the engine with the electric motor.

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The 80% to 30% usage is really intriguing. What if after more research GM realizes that the battery can be used optimally from 100% to 0% range?

The opening up of that extra 50% reserve is just a software update away and suddenly you have 80 miles range (50 to 100 miles depending on how you drive - to be politically correct) plus an additional 300 miles on gas.

The reason they keep the 30% reserve at the bottom end is they always want the reserve power for passing, rapid acceleration, or heavy hill climbing.

The reason they don't try to charge it over 80% is because it just isn't fuel efficient to do so and it's also better for battery longevity (as opposed to charge life). Li-Ion batteries just last longer if you don't always recharge them to full.

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I don't know... practically every battery I've seen loses its ability to store energy after many charge and discharge cycles. Perhaps one day, there will be batteries that last forever, but in the meantime, having a reserve makes sense. And anyway the Volt needs a buffer to perform well, since the generator makes less power than the electric motor needs.

I don't see how the Leaf will be in trouble if suddenly batteries last forever. In fact, I think EV cars will be even more compelling. The Prius can easily change to the Volt's design, because they both use planetary gearboxes and two electric motors to create an eCVT; Volt just adds a couple of clutches to completely decouple the engine with the electric motor.

I meant when the charge retention life is only two years then Leaf is certainly in trouble. Because the 100 miles will become less very soon. But if it is 10 years then it is obvious.

Certainly Prius can go Volt route, but then it will be like the pot calling the kettle black given that Toyota has gone on the record that Volt is inferior than Prius. It would be a vindication that GM was right.

The reason they keep the 30% reserve at the bottom end is they always want the reserve power for passing, rapid acceleration, or heavy hill climbing.

The reason they don't try to charge it over 80% is because it just isn't fuel efficient to do so and it's also better for battery longevity (as opposed to charge life). Li-Ion batteries just last longer if you don't always recharge them to full.

I understand that part, that is why I said on further research. What is to prevent the engine from replenishing the battery faster if a superior system comes into picture or that the Li-Ion batteries are done away with the charge memory? GM is applying a factor of safety by limiting the range of usage till more research is performed. It may even not use the remaining 50% but it certainly does not prevent from using that if the research proves so.

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Iunderstand that part, that is why I said on further research. What is to prevent the engine from replenishing the battery faster if a superior system comes into picture or that the Li-Ion batteries are done away with the charge memory? GM is applying a factor of safety by limiting the range of usage till more research is performed. It may even not use the remaining 50% but it certainly does not prevent from using that if the research proves so.

Well one of the limiting factors is the size of the regenerator. It's 55kw... it's only going to put out so much energy at a set RPM. Charging the batteries faster may be possible, but not without heat concerns.

Yes I know there may be further developments in the future... but I don't think you'll be seeing a Firmware update for the Volts being produced today.

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The 80% to 30% usage is really intriguing. What if after more research GM realizes that the battery can be used optimally from 100% to 0% range?

The opening up of that extra 50% reserve is just a software update away and suddenly you have 80 miles range (50 to 100 miles depending on how you drive - to be politically correct) plus an additional 300 miles on gas.

They already did open it up to ~9kWh.

Although some of the reviewers are managing to put the Volt into limp mode with very aggressive driving (probably for extended periods) and they had to add the mountain mode. It doesn't sound like this would be a problem day-to-day, but I'm not sure how much farther they want to push it for the reasons Oldsmoboi gave.

This is just one of the limitation of the Volt design.

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Certainly Prius can go Volt route, but then it will be like the pot calling the kettle black given that Toyota has gone on the record that Volt is inferior than Prius. It would be a vindication that GM was right.

You'll have to forgive Toyota for believing that their PIP solution (which offers 1/3 of the Volt range for 1/5 of the battery capacity, ~65% better ICE fuel efficiency, and at a significantly lower price) is the better solution. They've probably got a leg to stand on.

Also, pots and kettles and all that, GM seems to have gone more the Prius route than they had initially claimed in order to improve efficiency.

I understand that part, that is why I said on further research. What is to prevent the engine from replenishing the battery faster if a superior system comes into picture or that the Li-Ion batteries are done away with the charge memory?

The Volt could charge the battery (as they do with mountain mode), but pretty much any charging of a plug-in's battery is inefficient. That is why they don't.

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Does this dual use component make the Volt a hybrid and not an EV? Well we have to go back to the original question of, "What make a car a hybrid?" The Volt can be operated at any speed and at any level of acceleration without the gasoline so much as twitching.

It CAN, but more importantly, it DOESN'T.

The Prius, even the coming plug in model, can't do this.

So if the Prius was given a significantly more powerful electric motor would it no longer be a hybrid?

The Prius can move on any combination of motive power. The Volt's only motive power is electrical.

Not true, the ICE does provide assist to the Volt's wheels.

The Prius can be driven without any electrical assist at all. In Volt, if your batteries ain't glowin, you ain't goin.

So each needs one form of power to operate and can utilize the other, and that makes one a hybrid and the other not a hybrid?

That the gasoline engine can assist the smaller electric motor under certain conditions, doesn't make it any more a hybrid than the burned out starter on my dad's F-250 was.

For future reference, exactly how much ICE assist does it take before it "counts"?

Personally, I don't understand this argument. GM has indicated that both the ICE and the motor will power the wheels. Case closed. Why the semantics to try to cast it as something else? I have to assume it is because so many people decided it was necessary to define the Volt as being a success based on how much it was unlike the Prius. It is a bad stand to take, because Volt 2.0 is going to be even more like the Prius (they may even hit the magical 80% ICE assist that is recognized as the Intergalactic Hybrid Cutoff).

Edited by GXT
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It CAN, but more importantly, it DOESN'T.

Yes it DOES. If you pull out of your driveway with a FULL charge and then floor it, the Volt will operate 100% electrically until the battery reaches it's bottom threshold... even if you're going 100mph.

The Volt has 4 modes of operation:

EV mode 1 motor - This uses just the main traction motor at all speeds under 70mph.

EV mode 2 motor - This uses both the main traction motor and the 55kw regenerator motor at speeds over 70 mph.

In neither of these modes is the gasoline engine running.... doesn't matter if you're going 100mph or 10 mph.... no gas is being used.

The other two modes happen when the battery reaches it's lower charge threshold and are"

Regeneration mode 1 motor - Speeds below 70mph, The car is being propelled by the primary traction motor and the gasoline engine is spinning the 55kw regenerator motor to maintain average battery level.

Regeneration mode 2 motor - Speeds above 70mph, The car is being propelled by both the primary traction motor and the secondary 55kw regenerator motor, the gasoline motor is helping to spin the 55kw motors

If, for whatever reason, you were to cut off electrical power to the two motors, the Volt would slow to a stop with the gasoline engine spinning freely. Take away the battery, even with a full tank of gas.... and the Volt isn't going anywhere, even above 70mph.

So if the Prius was given a significantly more powerful electric motor would it no longer be a hybrid?

If that was the only change, the Prius would remain a hybrid, albeit a faster one. The nature of the Prius is that the motion of the vehicle is created by gasoline, electricity, or both. These multiple locomotion sources are what makes it a hybrid. In the Volt, motion is only created from electrical power. The gasoline engine never contributes torque to the wheels. It only contributes torque to the secondary electric motor.

Not true, the ICE does provide assist to the Volt's wheels.

false

So each needs one form of power to operate and can utilize the other, and that makes one a hybrid and the other not a hybrid?

It's the Pruis' ability to blend the motive power sources that makes it a hybrid. Volt does not have this ability. All motivational power comes from the electric motors.

For future reference, exactly how much ICE assist does it take before it "counts"?

It takes the ability to move the vehicle in a drivable manner.... that was the whole point of this article.

Personally, I don't understand this argument. GM has indicated that both the ICE and the motor will power the wheels. Case closed. Why the semantics to try to cast it as something else? I have to assume it is because so many people decided it was necessary to define the Volt as being a success based on how much it was unlike the Prius. It is a bad stand to take, because Volt 2.0 is going to be even more like the Prius (they may even hit the magical 80% ICE assist that is recognized as the Intergalactic Hybrid Cutoff).

You've had a bee in your bonnet since the Volt program has been announced. I don't know if it was your Tide bottle they used as the show car's engine and you just took it that personally or what.

GM has said "There is no physical connection from the 1.4l to the wheels."

They already did open it up to ~9kWh.

Although some of the reviewers are managing to put the Volt into limp mode with very aggressive driving (probably for extended periods) and they had to add the mountain mode. It doesn't sound like this would be a problem day-to-day, but I'm not sure how much farther they want to push it for the reasons Oldsmoboi gave.

This is just one of the limitation of the Lithium Ion Battery

Fixed

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Deep discharge cycle endurance is not a forte of Lithium Ion cells. This is not a matter of GM's research or the lack thereof. It is a matter of the chemistry of choice. In general Lithium Ion cells are good for power density, but not particularly good in cycle endurance. NiMH is actually better in this respect (by about 20%).

People like to think of the Lithium Ion battery as one type of battery. It is actually an extensive variety of very different battery chemistries that happen to share the use of Lithium compounds in its electrolytes and cathodes. Cathodes can be Lithium Nickel Oxide, Lithium Cobalt Oxide, Lithium Manganese Oxide, Lithium Iron Phosphate or some other (more complex) Lithium compound. The electrolyte is a matching lithium salt solution. In general, there is an inverse relationship between cycle endurance and energy density. Lithium Iron Phosphate for instance is great in endurance, but is near the bottom in energy density. In a car where the battery is already the biggest single real estate and weight adder, it is a balancing act between getting the power pack small and light enough yet having high storage capacity and having a high endurance pack that lasts longer but holds less. Right now the math works out that using the high density chemistries, but using only a portion of the charge capacity is smaller and lighter than using a high endurance chemistry and using a fuller range.

Edited by dwightlooi
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Awesome article...I've been really pissed at the way people have reacted to this mews. Just as this article states there isn't a vehicle on the road like the Volt and the Volt should not be compared to the current hybrids on the market...if other manufacturers adopt similar technology and want to call the cars hybrids, whatever, but it is pretty obvious that the two aren't the same and I hate to say that it just seems like everyone takes a stab at GM first chance they get...Toyota can be found to have covered up all kinds of illegal activity surrounding their vehicles and yet the problems about GM echo in nearly every article you read regardless of the product being reviewed being an outstanding product.

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"If it only uses this much electricity, is it still a hybrid?"

If I cross-pollinate two different flowers, is the result a hybrid?

Yes, yes!!

I don't get why anybody thought the Volt wasn't a hybrid in the first place. (Yes I do: GM's marketing said so.)

hybrid (n): Something of mixed origin or composition.

I don't care if it runs on a combination of monkey dreams, pixie dust, and children's tears—if it has more than one energy source, that's hybrid power.

No matter how few tears it uses.

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I don't care if it runs on a combination of monkey dreams, pixie dust, and children's tears—if it has more than one energy source, that's hybrid power.

No matter how few tears it uses.

This would be correct.

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The confusion is with where you are measuring, not what you are measuring.

Everyone's natural tendency is to measure what you put in the car to determine if it's a hybrid..... but a car is more about the motive power. And in the Volt, the motive power comes from the electric motors.

We don't call Flex-Fuel vehicles hybrids just because they can run two different fuels do we?

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