On Oct. 28, GM hosted a Chevrolet Volt web chat, where participants could ask questions to the following two panelists: Pete Savagian, GM's chief engineer of electric motors, and Lindsay Brooke, an editor with SAE International's magazines group who writes about technologies in the global auto industry, as well as new vehicles, and has covered the Volt's development.
The Volt experienced its best sales in October at more 1,100 vehicle deliveries, according to GM’s Nov. 1 sales report.
Q: Is there any reason traction motors such as used in the Chevy Volt can't be designed to allow being deliberately over-driven momentarily (a few seconds only) to improve 0-60mph and/or 45-85mph times?
Savagian: The Voltec is a fully integrated propulsion system. So speeding up the 0-60 time, or 45-85 mph time you are referencing, would mean not only changes to the motor but also the power electronics, the battery and the controls. Not a simple change.
Q: When I first got my Volt two months ago, it charged to 40 miles. Now it is only charging to 35 miles and saying that it is fully charged. I hear this will happen in the colder months, but why? If it is pulled in shouldn't it always charge to the absolute fullest?? BTW when I first got the car I was using 120-volt charger and now I have a 240-volt charger.
Savagian: The battery is actually charging to "full." However, the range estimation varies based on your driving behavior and your use accessories, such as heating and air conditioning. Monitor your efficiency gauge to improve your battery range performance. The estimator will follow. The range estimator will improve as your actual driving range improves.
Q: Why does Cadillac only have one hybrid vehicle, I know there are plans to give the SRX a system like the Volt, but what about sedans besides the XTS what about the ATS and the CTS?
Brooke: You gotta be patient! GM Powertrain has a portfolio of various hybrid and EV solutions in the works, some of which will be applied to Cadillac future models as appropriate.
Q: What is the estimated operating life of a traction motor such as those used in the Chevy Volt?
Savagian: We validate our electric motors to three lives. Each life is 200k miles of what we would consider a harsh driver, so they are very reliable and durable.
Q: Is GM working on electric motors that do not require rare earth metals and if so, what are the advantages/disadvantages of the alternate technology. Could you explain the difference?
Savagian: We certainly are. In fact, GM has just launched the eAssist program in the Buick Lacrosse that uses an induction motor and has no rare metals. Induction motors work well in high speed and light load applications, like eAssist.
Q: Is it possible to pair a hybrid system with clean diesel?
Brooke: The clean diesel/hybrid pairing is indeed possible. It's most common in the U.S. currently on urban buses (Ann Arbor, MI, is full of them, and the diesels are running on a biodiesel blend). Peugeot is the first automaker (its 3008) to offer this powertrain in production. The challenge is the high cost inherent with diesel engines (reinforced block, cylinders, common rail fuel system, turbos, etc.) combined with the (currently) high cost of batteries on the hybrid side.[PAGEBREAK]
Q: Should you only charge the Volt when you can charge it to complete or is it okay to charge it after driving it say 15 miles to work and leave on charge until you need to drive somewhere again. Will this make the battery have a short memory so to speak like when you charge a cell phone battery?
Savagian: Charge anytime you like at any opportunity. There is no memory affect. The more energy you put into the car from the grid, the less gas you will use.
Q: The Cruze gets a diesel next year — could that work in the Volt Gen-2?
Brooke: GM could pair a small diesel with the Voltec system, but I'd bet that such a combo won't end up in Volt gen2. I'd bet that GM continues to optimize its gasoline engines for future Volt duty--or even develop a specific ICE for E-REVs. I can't wait to check out the diesel Cruze.
Q: I’m a firefighter and use the Jaws of Life frequently, where is the main electrical harnesses located on these cars so we don’t cut thru them and get a nice electrifying surprise?
Savagian: We've done a lot of training nationwide with first responders on this very subject. We have labels under the hood and in the rear of the vehicle that indicate cut points for the high voltage cabling in the event that power needs to be disabled. Consult with the National Fire Protection Association to get more details on our training.
Q: If as you say you validate your electric motors to three lives & each life is 200k miles, does that mean one could expect a life of 600K miles?
Savagian: Yes. It is reasonable to expect that.
Q: As the weather is getting cooler here in Michigan, I am finding that my Volt is not charging as many EV miles, I used to get 40-43 and am not averaging about 30-33. It has been in the 40s-50-s and is garaged at night. Is this normal or are there problems with my battery?
Savagian: Your vehicle will actually use more energy as the weather gets colder. We are confident there are no problems with your battery, but we have said that performance will vary based on the three T's: terrain, temperature and technique of the driver.
Q: What is the difference between the Volt and the Plug-in Prius?
Brooke: The Prius PHEV has a bit larger battery than the standard Prius, giving it modestly greater (accent on the modest) EV-only range. I've driven the PHEV and found that it runs on the combustion engine in most driving situations. It's not even close to Volt in terms of being a satisfying ride in electric-mode.
Q: So induction motors would not be appropriate for the Volt, which requires a motor to meet a heavier load application than eAssist?
Savagian: That is correct at current levels of technology, but we are always looking for ways to improve our electric motors.
Q: Now that the Tesla Model S is claiming 300 miles of range (even a recent statement of 320 miles) and AC charging time of 3.5 hours (on a 70 amp circuit) and 45 minutes on an 80 amp DC circuit, don't you think the evolution to all-electric will go pretty fast? (as in 5-8 years) In other words, the Voltec architecture, as awesome as it is, perhaps will simply be eclipsed by all-electric?
Brooke: I don't think the introduction of Model S will accelerate the public's move to vehicle electrification to a great degree. The Tesla car will be a pretty marginal player. In fact I'm trying to think what its major appeal will be--that it's made in California? It's an attractive sedan, but in the next three years the U.S. market will have (by my count) 10-11 new advanced hybrids and EVs entering the scene. And, perhaps unfortunately for electrification, gasoline prices remain LOW relative to the cost of developing these systems. Two weekends ago on a trip to Dayton, OH, I paid $2.99 a gallon for regular![PAGEBREAK]
Q: What is the reason the Volt does not recharge its batteries while driving on the highway, after depleting the original charge?
Savagian: The most efficient charging solution is to arrive at your destination with the ability to take on as much grid electricity as possible. When you recharge the battery with the engine you are in essence powering up with gas, which is more expensive and isn't as clean as grid electricity.
Q: Do you for see new battery technology in a decade - like announcements recently about a solid-electrolyte batteries and mesh-style batteries - both offering replacement of Li-Ion and Li-Poly chemistries?
Brooke: The global battery industry is working flat out on R&D for new cell chemistries and approaches to battery pack design. There are many variations of Lithium chemistry being tested. Most industry experts in the battery field tell me, however, that Lithium-ion chemistry will be the dominant chemical over the next decade at least.
Q: Are there any plans to increase the efficiency of the motor at higher RPMs and eliminate the need to couple to the ICE at speeds of 70mph?
Savagian: It isn't based on speed, it is based on load. We are always trying to make the motors more efficient. However, the output split mode has a ten percent or greater efficiency advantage at highway speeds.
Q: Premium unleaded or regular unleaded in the Volt?
Brooke: The Volt's combustion engine is calibrated for premium fuel, which GM recommends.
Q: Ouch 3.55 a gallon +/- for premium here in NW Georgia.
Savagian: most Volt owners are filling up the 9 gallon fuel tank once every 30 days. In most areas, premium fuel costs about .20/gallon more or $1.80 per month. It's a small price to pay considering most of the other miles driven (electrically) are roughly 1/4th the cost per mile.
Q: I'm kind of afraid that I'd get a Volt, and within a few years the technology would blow up to some new level.
Brooke: By "blow up" I'm assuming you mean the technology will change profoundly and possibly becomes obsolete as a new one comes in. I wouldn't worry about the Voltec system becoming obsolete any time soon. And, the current system is very amenable to electronic/software upgrades.
Q: How do you tell the AC induction motor which direction to turn for forward or reverse? Is it just a couple of extra windings to start it in the right direction?
Savagian: The motor is controlled with a three-phase variable frequency inverter, unlike single phase 60 hertz current that comes out of the wall. Direction and torque are both under closed loop control.
Q: Honda's CRZ hybrid shows that you can buy a cheap, yet fun to drive hybrid and improve on its performance with aftermarket parts. Will there be a model that will compete with the CRZ?
Brooke: GM Powertrain is crankin' hard on developing a broad portfolio of vehicle electrification solutions for various applications--from small cars like the upcoming Spark EV to full-size trucks. I'm not that impressed by the CR-Z because it doesn't seem to move the efficiency needle as much as it should in such a small vehicle. I think you should look forward to small, sporty electrified vehicles from GM in the future.
Q: Does the speed control oscillate power under steady (hwy) conditions so that the power is not at a constant draw from the battery? I've heard highway driving only needs 15-20 hp at most on flat ground.
Savagian: when we're under speed control power varies with headwind and grade, but it is a matter of the weather conditions and your terrain.
Brooke: The industry is exploring many, many different charging technology options, aimed at speeding up the EV charging process. Don't forget, we're used to filling a 20-gallon gas tank from the pump in about 4-5 minutes. That's the benchmark for EVs. Higher voltage solutions may come into play once power sources, local infrastructure, and safety issues are addressed. 600V? For large vehicles perhaps (EV city buses).[PAGEBREAK]
Q: Is it possible/practical to get the same amount of regen braking in D gear, with careful application of the brake, as it is in L "gear"? I would like to avoid applying the hydraulic brakes unless it's really necessary. Is there any way I can know that I'm accomplishing that?
Savagian: use the L gear to maximize your regen.
Q: In case of an accident can the batteries explode?
Savagian: You shouldn't have any concerns about the Volt battery "exploding." We've conducted extensive testing on the battery both on the road and in the lab. But don't take our word, the Volt received a 5-star rating from NHTSA and is an IIHS Top Safety pick
Q: Lots of techie people perceive Ford as making the most technologically advanced vehicles due to their SYNC cabin tech which is available even in some of their lower cost models, but they have yet to produce a vehicle as technologically advanced as the Volt. Any plans to incorporate the Cadillac's CUE tech into the technological powerhouse that is the Volt?
Brooke: The pace of GM (and other automakers) integrating new electronic technologies in their production vehicles is staggering, actually. Don't overlook GM's OnStar integration in the current Volt. But I think you're on to something about the CUE technology--it would make sense in an EREV!
Q: Any plans to put smaller traction motors in each wheel for an AWD experience?
Brooke: I've written about various wheel-motor programs in the industry. Companies like Protean Electric (from the UK). GM investigated wheel motors in the early 2000s. The challenge is the dramatically heavier unsprung mass that these wheel motors add to the vehicle. But the technology is attractive in creating a super-AWD EV.
Q: Can you give us any estimate of the amount of a Volt's kinetic energy that can be captured as battery charge during regen braking under ideal circumstances?
Savagian: We can recapture about half of the kinetic energy. The other half is lost to aerodynamic drag, rolling resistance and to electric power generation and storage losses.
Q: Did you start making the blue color Volt yet? I haven't seen one on the street.
Savagian: We just began producing Blue Volt's. In fact we have two out on our Milford Proving Grounds already. Very sharp.
Q: How long does it take to charge a Volt?
Savagian: using the 120V charger provided with the Volt it takes about 8-10 hours. If you opt for a 240V charger that time is cut in half to about 4 hours.
Q: Was there any experimentation done in developing the Volt, to using Hydraulic motors driven by the electric motor to drive the wheels?
Brooke: Hydraulic hybrids show good promise in medium-duty and larger trucks, because those vehicles have the space within their frame rails to package the hydraulic pumps, accumulators, etc. The US military is very interested in this technology. It also makes sense for any vehicle that is hydraulics-intensive (refuse trucks, backhoes, etc.)
Q: If a traction motor should fail, any idea (ballpark est.) of the replacement cost?
Savagian: We test and validate our motors to operate for at least three lives (200,000 miles each) and we warranty them for 8-years / 100,000 miles. So rest assured — we don't expect you to have to deal with replacement costs any time soon.
Q: Have you heard of Electric Motor Cars - they claim 200 mile range using a sodium-based (and rechargeable) battery. Why do we keep focusing on Li-Ion when that really doesn't seem like the best direction?
Brooke: Outside of the world's major automakers, there are quite a few small players who have emerged in the EV and hybrid space. Many of them claim to have a technology that's unique. But I don't trust their R&D chops, their engineering, testing, and overall seriousness in the market. Why would I spend money with EMC when within the next 24 months I'll have a smorgasbord of new EVs made by reputable global automakers from which to choose? Too risky, those emergent automakers, for my wallet...
Q: When I had the computer update on my 2011 the miles on each charge dropped substantially. It went from the high 40's to the 30's. Is there anything that can be done to improve it to its former level?
Savagian: when the refresh occurs, it re-sets the charge algorithm to its factory setting (35 miles). It'll take about 100 miles before the vehicle "re-learns" your driving style.