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GM Provides Snapshot of State of the Volt; Tracking to Production in Nov 2010

4 April 2008

Voltpacks
The T-shaped Li-ion packs undergoing cycle testing in the battery laboratory in Michigan. The pack from Continental/A123Systems is on the left; the pack from CPI is on the right. The slot in the middle of each pack is to accommodate a structural beam that runs across the breadth of the car. Click to enlarge.

In a day-long briefing at the GM Tech Center in Warren, Michigan, the GM team responsible for the Volt provided a snapshot of the current state of development of the extended range electric vehicle (earlier post)—which is tracking to production in November 2010—to an international group of journalists.

The accelerated development of the Volt is pushing GM to design, to develop and to test in parallel the powertrain and the vehicle. Key topics addressed during the briefing were the cycle life and calendar life testing of the lithium-ion battery pack; the coming integration this month of the first packs into the mules; other powertrain and exhaust system issues; aerodynamic modifications to support the 40 mile all-electric range; and design issues.

The battery packs and the powertrain. GM has received initial packs from both CPI and A123Systems. General parameters of the packs are an energy capacity of 16 kWh; weight of about 170 kg, length of about 1.8m. The packs, which are based on prismatic cells from each company (the prismatic cell is GM’s go-forward design choice for energy batteries and perhaps even power batteries, according to Denise Gray, Energy Storage Devices and Strategies Director) need to:

  • Provide sufficient power to accelerate the vehicle from 0 to 60 in 8.5 seconds; deliver passing capability; and deliver “predicted driveability”.

  • Provide sufficient energy to support a 40-mile all electric range under city and highway driving conditions.

  • Have a cycle life that supports 150,000 miles under mixed electric vehicle (EV) charge depleting and extended range (ER) charge sustaining modes of operation.

  • Have a calendar life that is more than 10 years under real world conditions.

GM and its suppliers have already undertaken the cell level testing that has assessed the capability of each type of cell (CPI uses a manganese spinel chemistry, A123Systems a nano-phosphate chemistry) to achieve the required vehicle performance along with accelerated life testing and abuse behavior.

GM is currently engaged in pack level testing (cycle life, calendar life, temperature and vibration). The third major test set will be the dynamic testing of the packs in the mules and then in the production version of the Volt under road conditions.

GM also plans to test charge integration under a variety of simulated conditions (110V, 220V, presence of appliances such as washer/dryer or freezer in the garage, etc.), brownouts, blackouts, and so on.

The dynamic testing will begin following the integration of the first packs into E-flex mules (based on the Malibu) later this month. That will proceed in parallel with the pack-level tests in the battery lab that will continue for almost two more years—the shortest amount of time into which GM could compress testing to validate the required 10-year, 150,000-mile lifespan of the packs.

GM’s Cycle Test for the Volt Packs
ModeCycleTimeMilesCum.
Miles
EV Urban 23 min. 7.5 7.5
EV US06 10 min. 8.0 15.5
EV Hwy. 13 min. 10.1 25.6
EV Urban 23 min. 7.5 33.1
EV Urban 23 min. 7.5 40.6
ER US06 10 min. 8.0 48.6
ER Hwy. 13 min. 10.1 58.7
ER Urban 6 min. 2.0 60.7

For the cycle testing, GM is using a two-hour combination of the US urban, highway and the more demanding US06 cycles for the discharge; re-charging for three-hours; and simulating parking for 3 hours. This pattern will run 24x7 for two years on each of the packs. Although the packs are designed to be liquid cooled, the testing on the packs is being done without the cooling. The battery cycling testing is being done at the GM test facilities in Warren and in Mainz-Kastel, Germany.

Although the pack is sized overall at 16 kWh, GM plans to use only 8kWh in operations—i.e., a state of charge depletion window of around 50% (the pack won’t be charged fully to 16 kWh, because with a full pack, the first regen event would begin overcharging the battery). That 8 kWh needs to be deliverable at the end of the battery’s 10-year life, therefore GM is building in a buffer with the 16 kWh pack.

With future iterations of the powertrain, GM may begin expanding the SOC window, and/or begin implementing minor changes in the batteries.

Although the sizing of the pack is conservative, GM’s projected consumption of 200 Wh per mile (8 kWh over 40 miles) is somewhat aggressive. The team is confident in that figure, according to Frank Weber, Global Vehicle Chief Engineer, Chevrolet Volt and E-Flex Systems, because of the testing, modeling and simulation work that they have already done. Nonetheless, the sizing of the pack provides a buffer.

The E-Flex mules that will receive the Li-ion packs for battery testing have already been in operation at the Proving Grounds for 6 months, according to GM, with NiMH packs as the energy storage system. The focus to date with the mules—which implement full E-Flex systems—has been bringing them up to the state of readiness to accept the Li-ion packs and begin dynamic testing. Work on the mules has included:

  • Software function and integration testing;

  • Preliminary proof of concept; and

  • Calibration of the regenerative braking system.

The mules (one of which was on a lift with the Li-ion pack stationed beneath it) have been in operation 6 days a week for two shifts a day. GM expects to have a fleet of Li-ion equipped mules in operation by the summertime.

Over the next six months, GM will be focused on three primary areas with the powertrain: battery state estimation; thermal development; and propulsion development. The latter area includes refinement of the all-electric drive mode, hardware testing in EV mode, and further development of the power electronics.

GM has yet to finalize its selection of the combustion engine component of the powertrain, although the engine will be from its Family 0 of European small-displacement engines (1.0-, 1.2- and 1.4-liter).

GM is opting for a smaller fuel tank than originally conceived to reduce vehicle mass. The tank under consideration will still provide a 400-mile combined range, and GM decided to do as much as possible to ensure its 40-mile all electric range rather than “go overboard” in other areas, such as extended vehicle range. In recognition that the Volt (ideally) will operate for long periods of time without using the engine, GM has modified the fueling system to be able to eliminate evaporative emissions.

Aerodynamics. The inflexible design point of delivering 40 miles all-electric range under a variety of conditions with sprightly performance have forced GM to put a great deal of effort into the refinement of the exterior shape of the Volt. The impact of incremental improvements to the coefficient of drag makes a significant difference at highway speed—much more so than the weight of the vehicle.

The electric range of the Chevrolet Volt is most sensitive to improvements in aero, which is in contrast to a traditional vehicle program in which mass typically plays a larger role.

—Frank Weber

Changes to the shape of the production Volt compared to the show car that GM was prepared to discuss at the briefing included a longer front overhang; more rounded front corners, rather than the sharp corners of the show car; a slightly higher roof; and some modifications to the rear.

GM showed a 1/3 model of the production design of the Volt in the wind tunnel at the company’s aerodynamics lab in Warren, and uncovered small sections (front corner, rear corner) of full-size clay models of the production Volt in the design studio.

The interior. The shape and placement of the battery has pushed the occupants outboard, or to the sides of the vehicle, so the design team worked with the sections of the roof structure and doors to enable aerodynamics and provide adequate head room. The interior will accommodate a 6-foot 2-inch (99th percentile) male comfortably in the front and rear seats.

GM says it is putting a great deal of effort into the development of the human-machine interface for the Volt, although no examples of that were shown during the briefing.

We are looking for an i-Phone like experience.

—Frank Weber

Green Car Congress attended the briefing at GM’s expense.

April 4, 2008 in Electric (Battery), Hybrids, Plug-ins | Permalink | Comments (71) | TrackBack (0)

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Comments

Oh My!.. what is it called when you lust after a car? :)

... Male.

That would be car lust. ;)

I for one will stand in line for this car. If GM does the right thing, I think I won't be the only one.

Stephen

need to get this in before the board turns into a gm-bashing contest:
i applaud the engineers at general motors. it is real easy for environmentalists (which i am sometimes) to command engineers (which i am all the time) to "make a better, more efficient product".
how is toyota coming along on their PHEV project? last i heard they were getting disappointing results from their li-ion tests.. i wonder if GM will encounter similar complications.

marc:

EEStor may come to the rescue. With at least twice the energy density and up to 1,000,000 cycles, lithium batteries won't stand much of a chance for year to come.

It sounds like GM are learning a lot from this in terms of energy restricted transport.
Lets hope they apply it to the Volt and to the rest of the range as the models turn over.
If they just applied the aerodynamics to ICE cars, it would make quite a difference.
So good luck to them, and lets hope they succeed.
As Dr. Strangelove says ... "is is only a matter of willpower" ( and money ).

This makes me want to believe...

Maybe the term would be autolust, but that just does not sound right :)

This is fantastic. We are in the midst of an "arms race" for efficiency. Something I've waited my whole life for. Let's hope this long overdue way of thinking makes it to the production line. I am cautiously optimistic...

I doubt GM very much will have this 'Volt' in production by 2010. Since there would already be reports and photos of the pre-production 2010 prototype 'Volt' cars being tested on the roads of America like the 2010 pre-production Camaro.

Do the guys (and possibly gals) who test the batteries really wear lab coats or was that just for show during the tour? I know it's a dumb question but I had to ask after seeing the photo above.

With this kind of movement from GM I don't think my kids will be driving ICEs. Great.

I think they'll have it production by 2010. They are staking alot of their reputation on this - they are doing tasks in parallel (not the standard process) to get it to production faster.

They should be applauded for their work - and being very public about it. It will be very difficult for them to back away - this has been their poster-child.

Shane

"EEStor may come to the rescue. With at least twice the energy density and up to 1,000,000 cycles, lithium batteries won't stand much of a chance for year to come."

EEstor have made big claims and so far have very little to show for it. despite the fact that big (almost impossible) claims wow the crowds and the journalists, most of the time technological progress is made through small incremental improvements, and all the better for it. don't bet the farm on vaporware, is what I'm saying.

I should add - I have been to technical conferences where this was discussed years ago - some engineers wondered if it was a publicity stunt - but high level DOE officials indicated GM was heavily investing manpower, even at that time. It has only accelerated from then.

If GM beats Toyota to a good plug-in vehicle, it will steal Toyota's thunder. If GM pulls this off, they deserve wide and loud praise.

If the price tag is so high no one can afford it then this is for nothing. It must be priced for the working people at Wal-Mart or the poltry packing plant.

"The interior will accommodate a 6-foot 2-inch (99th percentile) male comfortably"

Well... there goes my dream of owning a Volt in 2010... I'm 6-4. :-(

I am wondering how much the Volt will weight with 170Kg of battery on top of an ICE engine, a 100KWhrs electric engine plus a generator of 50KWhrs. Probably close to 2 tonnes (4200 pounds) sure GM has a lot to learn how to save weight on the rest of the car to reach a decent mileage otherwise kiss the efficiency.

dont forget there is no transmission.. and they plan to use a small 1.0 liter engine.. so much less than 4000lbs.

My thoughts on EESTOR:
If what they have is for real they would not signed an exclusive agreement with ZENN, it would have been with GM instead - thinks about it!

"If the price tag is so high no one can afford it then this is for nothing. It must be priced for the working people at Wal-Mart or the poltry packing plant."

Just Watching: Get a job! (or a new one)

There are 100,000's that will buy this car even is it is $40K.

by aaron
"The interior will accommodate a 6-foot 2-inch (99th percentile) male comfortably"
Well... there goes my dream of owning a Volt in 2010... I'm 6-4. :-(

Arrrgh... I also am 6'4" It's just unreal how GM wants to reject a "growing" segment of the population, 6 foot plus people. I'm not asking for much... just a car that I can sit upright in. If GM feels compelled to maintain low hanging ceilings in their cars why can't they design the seat to accomodate 6 foot people??? It's crazy! Design the electric seats to run to the floor, even lower into an indentation in the floor if necessary. Wagoner looks taller than Lutz, can he sit in the car and look out the windshield with his head upright not pressing against the headliner or looking through the blue sun tint band or retracted sun visor? It's just amazing, they want to sell cars and yet, they don't. [sigh] Aaron and I are not the only "tall" people out there. Isn't it interesting that Lutz and Wagoner are tall. Has GM ever reasoned that maybe tall people get noticed and just might have more opportunities for promotion and a higher income than less average height individuals. GM is missing out on $$$$ by not sliding their percentile toward the tall end.

"Do the guys (and possibly gals) who test the batteries really wear lab coats or was that just for show during the tour? I know it's a dumb question but I had to ask after seeing the photo above."

Of course folks in labs wear lab coats. The lab coats and jumpers are part of the Personal Protective Equipment (PPE), just like the safety glasses and safety shoes that they are wearing in the photo. Lab coats protect the wearer and their clothing from dirt, grease, and other nasty things that inhabit laboratories. Lab coats also mitigate the hazard to carrying harmful materials home on worker's clothing. Plus, lab coats can have decals or patches that encourage wearer's to be proud of their work group and their work. Work clothing also reminds the lab workers that their employer may actually give a cr*p about their comfort and safety. (Plus it is usually cheaper to clean a lab coat than replace stained shirts and pants.)

"Do the guys (and possibly gals) who test the batteries really wear lab coats or was that just for show during the tour? I know it's a dumb question but I had to ask after seeing the photo above."

Of course folks in labs wear lab coats. The lab coats and jumpers are part of the Personal Protective Equipment (PPE), just like the safety glasses and safety shoes that they are wearing in the photo. Lab coats protect the wearer and their clothing from dirt, grease, and other nasty things that inhabit laboratories. Lab coats also mitigate the hazard to carrying harmful materials home on worker's clothing. Plus, lab coats can have decals or patches that encourage wearer's to be proud of their work group and their work. Work clothing also reminds the lab workers that their employer may actually give a cr*p about their comfort and safety. (Plus it is usually cheaper to clean a lab coat than replace stained shirts and pants.)

need to get this in before the board turns into a gm-bashing contest:

So.... Where's the bashing? Is it possible that GCCers are not reflexive GM-haters? That maybe they only bash when the bashing is deserved? That when GM does something good, we applaud them? How 'bout that.

aaron,

Not to worry, I am 6'1" and I fit into a Fiero GT back in the day. Hope springs eternal.

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