GM-VOLT : Chevy Volt Electric Car Site

The two recent media test drives of the Chevy Volt’s in charge sustaining mode were seen as positive by 85% of GM-Volt.com readers.

Both reporters mentioned however that they could occasionally notice the generator revving after charge sustaining mode was well under way, though neither coud detect it when it first came on.

I was able to communicate with one of the reporters, Lindsay Brooke of the New York times, about his experience.

“Yes, when the ICE first kicked in (on an uphill climb) I could neither hear nor feel its engagement,” he said. “It was completely seamless. I only noticed it because I was keeping a close eye on the cluster—the icon noting battery charge changed over to the icon showing a gas pump which denotes the switchover and how much range remains using the generator.”

“The reason the ICE generator engages at random times is due to its current control regimen for charge-sustaining mode,” he said. “As the quote from Tony noted, the controls engaged the generator, then shortly thereafter called for another of the pre-set charging speeds (rather like, “Oops, I needed more juice than I previously anticipated.”).”

“It was not in situations where I was flooring the pedal, which as you know has no connection to the ICE’s throttle control. Nor was it necessarily in heavy-load situations. A couple times the ICE engaged when the car was going downhill, under what would be light load in a conventional vehicle,” he said.

Brooke added, “I think we’ll be pleasantly surprised when we drive the production-spec car.”

Andrew Farah, the Volt’s chief engineer explained to GM-Volt,” there are still points at which operation of the engine generator is more aggressive than we want it to be, and we want to make it operate less aggressively.”

He says the engine never generates more power than the car needs but may generate it more quickly than necessary. Engineers are able to vary power production by both varying the engine’s RPM and its load, and that along the RPM-load plane there is the third dimension of efficiency which has to be taken into account.

These variables are distinct from the NVH (noise-vibration-harshness) component which is what the customer actually perceives. The team must work within the constraint boundaries of the “NVH ceiling” at the high end and the permissible limit of dip into the battery reserve at the low end to achieve the lowest NVH possible at all times.

It is still at this point a work in progress.

Farah also notes that they don’t let the engine to run at all at low speeds because there is less ability to mask its noise.

Overall, 99% of driving in the integration prototypes is without audible engine noise, there are rare ocassional spikes of sound that the reporters noticed, which will be ironed out in time for production.

It’s hard to believe after nearly three years of debate we have finally gotten some independent third party observations on what its like to drive a production-intent Chevy Volt in charge sustaining mode.

I thought it would be good to review and summarize what the reviewers said, seek some clarification from GM, and see what we all think of it.

Acceleration
LeBeu: low center of gravity and “sportier” feel when accelerating, not a sports cars, instant torque gives you responsiveness, will surprise skeptics
Brooke:sport mode delivers more oomph than normal mode

Handling
LeBeu:great handling that would surprise skeptics
Brooke: car feels solid and planted on the road, minimal body lean in tight corners, low rolling resistance tires provide excellent grip

Transition from EV to CS Mode:
LeBeu: transition is disconcerting, needs to be smoothed out, no fall off in power, jarring
Brooke:engine’s initial engagement is inaudible and seamless

Sustained CS Driving  Requiring Power
LeBeu: N/A
Brooke: intermittent momentarily disconcerting engine revs with immediate disappearance of sound even though generator still spinning

Instrument Panel
LeBeu: loves green to yellow efficiency gauge, overall great
Brooke: N/A

Overall Impression
LeBeu:  very impressed
Brooke: behaves admirably, extremely refined

I had the chance to discuss these journalist drives with Volt vehicle line executive Tony Posawatz who explained things the following way:

Both Phil LeBeau and Lindsay Brooke had wonderful drive experiences. I was in the car with both of them for their drives.

Neither was able to detect when the engine came on, much different than a hybrid. We are still fine tuning aspects of how the engine modulated under different load conditions.
We want to make it perfect. We have the unique challenge of balancing the customer pleasability, efficiency and regulatory requirements.

The engine has certain RPM efficiency points but does vary when you demand more power. Our work now is to feather in the RPM changes and refine which is simple calibration work.
The charge sustaining or range extending experience will be somewhat different to what people are accustomed to just like EV driving is a different experience.
Most of the time you will never know the engine is on.

On the same day the Today Show ran its piece on test driving the Chevy Volt integration prototype, Lindsay Brooke, a reporter from the New York Times published his.

Brooks was the only other journalist so far besides CNBC’s Phil Lebeau to test drive the Volt in generator or charge-sustaining mode and has written about it.

His brief article entitled Life After 40 tells us what we’ve been waiting to hear, but maybe not exactly what we wanted to.

Brooks writes:

Like other reporters, I had already driven Volt prototypes in the battery-powered mode, and they were predictably smooth and silent. But for eventual Volt owners, a crucial — and so far unanswered — question is how the car will perform when the battery’s charge is depleted and all electricity is provided by an onboard generator, driven by a gasoline engine, that has no mechanical connection to the wheels.

Then as he runs the car’s electric range meter dramatically down to the zero mark, the moment we’ve all been waiting for occurs:

With the dashboard icon signaling my final mile of range, I point the Volt toward a hill and wait for the sound and feel of the generator engine’s four pistons to chime in. But I completely miss it; the engine’s initial engagement is inaudible and seamless. I’m impressed.

Good so far.  He finds that as he pushed the accelerator, the sound of the engine didn’t change.

But later as he’s accelerating around the test track he gets a little shock that he calls disconcerting.

A few hundred yards later, as we snake through the track’s infield section, the engine r.p.m. rises sharply. The accompanying mechanical roar reminds me of a missed shift in a manual-transmission car. For a moment the sound is disconcerting; without a tachometer, I guess that it peaked around 3,000 r.p.m.

He asks GM’s Tony Posawatz driving with him what just happened.

“The system sensed that it’s dipped below its state of charge and is trying to recover quickly,” apologizes Posawatz. “The charge-sustaining mode is clearly not where we want it to be yet.”

Huh?

He goes on to write:

Immediately the engine sound disappeared, although it was still spinning the generator. A few times later in our test, the generator behaved in similar fashion — too loud and too unruly for production — but there is time for the programmers to find solutions.

So there we have it, the first reporter in history to write about the Volt’s operation in generator mode, and its a bit of a mixed picture.

It seem to go on flawlessly but throughout driving apparently has spikes of on/off engine roars that he finds disconcerting and unruly.

Though not exactly a happy report, he concludes:

Throughout my test, the prototype behaves admirably. At its current state of development, the Volt is an extremely refined vehicle.

Looks like GM has a little more work to do.  But then again the experience may be a bit subjecttive.  We’ll wait to see what others have to say.

Source (New York Times)

A long awaited milestone has just been achieved, sort of.

For many months we’ve discussed, debated, deduced, asked about and imagined what it would be like to drive the Chevy Volt while its generator is running.

This mode is so critical because it represent the first mass market application an electric car operating at the same time an on-board gas engine is running to generate electricity once the battery low point is reached.  We’ve heard for months the process has been under refinement but that GM executives and engineers were already quite pleased with the experience.

Phil LeBeau of NBC’s nationally broadcast Today Show became the first person outside of GM to have the experience and be able to report on it.  He was given an exclusive test drive of an advanced integration Chevy Volt prototype.

The report did give us some new observations and knowledge. You can view the two minute video at the bottom of this article.

We found out the driver side LCD screen tells how efficient one is driving by showing a traffic light symbol that changes from green to yellow when efficiency reduces.

Chief engineer Andrew Farah demonstrates it; when he floors the car he says “it felt really great wonder full and responsive, it was terrible for overall energy efficiency ”

LeBeau also says on the screen the MPG is demonstrated and for example while driving around the Milford proving grounds on his exclusive test drive it showed he was getting over 200 mpg.

The report also claims JD Power thinks only 50,000 electric cars will be sold in 2015, a far cry less than Obama’s pledge of 1 million or the several million hoped for by the Electrification Coalition

Also, for the first time ever the pedestrian alert was demonstrated.  The Volt is nearly silent and wont make artificial sounds.  Instead a driver activated alert will be available to let people know the car is nearby  The alert is activated by pushing a lever and emits a pleasant light horn-like chirping sound.

In his written report, Lebeau comments on the driving experience:

When you go from driving all-electric to running the gas-assist engine, the transition is disconcerting.

It needs to be smoothed out, and GM engineers know it.

When you’re driving on the gas assist engine, there’s no fall off in power, handling, etc. and perhaps I found it jarring because I went from the silent electric drive to hearing the engine. Whatever the reason, it needs to be improved.

General Motors provided an online media update as to current progress on the Chevrolet Volt and battery development program, moderated by vehicle chief engineer Andrew Farah and Voltec battery system manager Bill Wallace.  I and several actual journalists attended.  We were given the current state of development and the roadmap of the next 12 months leading up to the retail launch.

Overview
To date GM has built 80 pre-production IVers and 300 packs. Those vehicles are in testing 24 hours/7 days per week. Production and process validation builds will be made at Hamtramck from March through August 2010. From August 2010 through November 2010 manufacturing validation builds will be made.

The current prototypes have been tested cumulatively over 1/4 million miles. So far they’ve gone through hot weather trials, mountain trials and 65% long distance calibration buy-off rides. In December they will undergo a 300,000 mile three-lifetime simulator test. “We’re very happy where we are right now,” says Farah.

Battery Update
In December 2008, GM built its first battery pack based on their own in-house design and so far over 250 of these 4th and final generation packs have been made.  No further refinements will occur, others at GM are working on lighter next generation packs.

GM will bring it own battery pack assembly plant online in January and it is currently being built-out.   The first pack to be made there will happen in February 2010, and the first saleable packs will be made in August 2010.  The battery lab is working to develop and refine the processes by which mass production of large numbers of packs is flawless.

Over 50,000 cells have been tested on over 300,000 simulated miles in the lab and to date not a singe cell failure has occurred.

Stress Testing
Cells are exposed to crush, penetration, thermal stress and overcharging.  Modules and packs have been exposed to crush, pressure, shirt circuit,corrosion, thermal stress, and seal integrity.  All is well.

Vehicle Stress Testing
Cars have been exposed to the twist ditch, water exposure, potholes, and vibration.  Crash test have shown battery remains safe at 30 MPH head on, as seen in the picture below.

Learnings
Farah admits NVH (noise vibration and harshness) has been “particularly tricky” especially in charge sustaining mode as the car was tweaked to be extremely quiet in electric mode.  Through changes such as increased insulation, specially designed instead of off-the-shelf bushings and new side airflow vents a pleasing experience has been obtained.

Battery chemistry had to be tweaked slightly to achieve longest lifetime, which will be effectively 10 years, though it was noted in temperate climates much longer lifetimes are possible.  Extreme cold and even more so extreme heat degrade the battery life expectancy.

“10 years is the target life, but depending on where you live, you could see significantly more than that,” said Farah. “In more benign conditions — if you do more city driving — and if you are in a more temperate area, the battery would last significantly longer.”

“But even if you live in Phoenix, as long as you charge at night, and you run during the day, your battery will remain happy,” said Wallace.

It has been found that the battery packs are well protected by the car’s structure and cells handle all abuse situations remarkably well.

Though I asked Farah, he still would not release the size of the gas tank claiming we won’t know until just before launch because its still being tweaked.  The gas engine will likely be programmed to circulate once per month even if the driver never uses it.

Farah also wouldn’t disclose the Chevy Volt’s curb weight though states its was “heavier than I would like.”  Efforts are being made to reduce weight of both the car and 400 pound battery pack.

GM has signed off on the final design freeze of the charging equipment, both 120V, 220V and the in-vehicle on-board charger.

Though not confirming dates, Farah implied he is looking forward to beginning work on the higher performance Cadillac Converj, which has unofficially been greenlighted for production.

Below is a video of the Chevy Volt battery pack undergoing serious crush testing:

I had the following discussion with Alex Cattelan who is the Chevy Volt’s chief powertrain engineer. She has a very deep understanding of how the car operates and recently drove in a fleet of integration Volt prototypes through rugged mountains of Knoxville Tennessee.

Do you feel the charge-sustaining (CS mode) experience is now pretty solid and are you pleased with it?
We are definitely pleased with the level of progression we’re at. We are right on track to where we need to be in terms of the next stages of development we need to do to meet our target. Is it commercial right now, no, but that’s why were taking the time to get it to be commercial. Does it have the capability of being commercial, absolutely. We’ve proven that to ourselves.

We just took our leadership through a test drive in Warren (Michigan) and comments are that they cant tell when the engine is coming on or off. Those are the kind of things we like to hear.

You drove the IVs around the mountains of Tennessee. What about those big hills and the generator. It sounded like it drove very briskly powerfully and effortless is that true?
Yes, absolutely. Some of our control capability to utilize the battery, the engine, and the motors and to be able to optimize for high load and low load situations we’ve been working on developing that stuff for the last year and half an I couldn’t tell you how happy I was when I was in Knoxville because that’s when I had the opportunity to see it all come together. A lot of those bits of software all came together on one trip and it was a joy to drive.

So you took it up some steep hills and mountains?
Absolutely. We were in the Cherokee area taking it up through those hills and a lot of situations following it. It was a very touristy area. Following the speed of traffic, absolutely no problem, and where I had opportunities I certainly like to push the limits of the vehicle, and we did on those mountains, and I could not get it to degrade in performance.

That’s in charge sustaining mode?
Certainly in charge depleting, we have no issues because we have battery power, I’ve got it all at my fingertips. Now in charge sustaining we know that the engine power is slightly less than the peak vehicle power but we have controls ways to manage that and to utilize the engine in conjunction with the battery to get a little bit of extra power when we need it, and replenish it back when we don’t.

I know the battery runs down to roughly the 30% level before for the engine comes on. Is that 30% itself the whole potential buffer band?
We certainly don’t utilize the full 30% but there’s a portion of that that we utilize as a buffer.

You wouldn’t go to zero ever?
No. When the engine cannot meet peak load requirements we’ll suck a little bit out of that buffer and as soon as we have a situation when we can, we’ll put it right back in. All the controls that we work do that to optimize not only the driveability but the efficiency as we’re doing it, NVH (noise vibration harshness) as we’re doing it, the total driving experience as well as to protect the battery from a life experience. This is what allows us to give really good warranty life on our batteries as we’re doing I all in a controlled fashion.

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