Will the Gen 2 Volt Use the Spark EV Traction Motor Design?

DEC 28 2014 BY GEORGE BOWER 14

Chevy Spark EV's Motor To Find Another Home?

Chevy Spark EV’s Motor To Find Another Home?

The all-new Voltec drive unit used in the second-generation Chevrolet Volt is 100 lbs. lighter and up to 12 percent more efficient than the previous system.

The all-new Voltec drive unit used in the second-generation Chevrolet Volt is 100 lbs. lighter and up to 12 percent more efficient than the previous system.

It will be just a little over 2 weeks until we get to hear the straight scoop from GM on the much anticipated Gen 2 Volt. Everything proposed in this article is an educated guess on the author’s part. It is meant more as food for thought than some sort of dictate on the final configuration.

We know the Gen 2 Volt will have 5 modes. The Volt’s new transmission is named the 5ET50. The first number in the designation is the number of modes the transaxle uses. The Gen 1 transaxle is named the 4ET50. Gen 1 has 4 modes…..gen 2 has 5.

What is this new Mode? We are fairly certain that the new mode is where we couple the Volt’s 2 motors together for more acceleration in EV mode. In gen 1, the 2 motors operate at different speeds. MGB (traction motor) has a 10,000 RPM speed limit. MGA is attached to the ICE so it has a much lower design speed than MGB. Thus one can’t just direct couple the 2 motors together.

Chevrolet Spark EV Coaxle Gearbox (click to enlarge)

Chevrolet Spark EV Coaxle Gearbox (click to enlarge)

Just as a little review, let’s look at the way gen 1 works in EV mode.

Figure 1

Figure 1

In gen 1, there are 2 EV modes: 2 motor mode and single motor mode. In 2 motor mode the 2 motors are mixing thru the planetary gear set. This mode is economy mode. Mixing the motors allows the designer to match the motors more closely to max efficiency.

Figure 2

Figure 2

The second Gen 1 EV mode is single motor mode. This is a very simple mode to understand. All we are doing is sending the power straight to the wheels thru some gear reduction sets. The ring gear is locked and we are sending the power thru a 3.24 gear reduction in the planetary gear set to a simple helical gear set of 2.16/1 ratio. The total gear reduction in this mode is 7/1 as shown in figure 3.

Figure 3

Figure 3

2016 Chevrolet Volt Will Be Fully Revealed At The NAIAS On January 12th

2016 Chevrolet Volt Will Be Fully Revealed At The NAIAS On January 12th

 

 

The Gen 1 traction motor spins at a max RPM of 10,000 RPM and goes thru a 7/1 gear ration straight to the wheels. This mode is used during maximum acceleration. If you step on it in EV Mode the car goes into single motor and will stay there all the way to 100 MPH.

The Spark EV uses an entirely different philosophy.

The total gear reduction in the Spark is only 3.87/1 versus 7/1 in the Gen 1 Volt. Spark gets away with this numerically lower gear ratio because the motor is a high torque motor capable of 400 ft lbs of torque.  It also runs at a lower RPM than the Gen 1 traction motor as shown in figure 4.

Figure 4

Figure 4

This means that the Spark EV traction motor RPM’s are more closely matched to MGA in the Volt as shown in figure 5.

Figure 5

Figure 5

This synchronicity makes for a very simple latch up for mode 5. The two motors are just linked together in a 1/1 speed ratio and the power goes straight to the wheels thru the final reduction set resulting in a much simpler and lower loss design, just like in the Spark.

What are the consequences of this proposed configuration?

Figure 6

Figure 6

Figure 7

Figure 7

So what do you readers think of this proposal? Got any better ideas on what the 5th mode is and how it will be implemented?

Hat tip to BillR and Walter. (They may not agree but they helped with the thought process)

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14 Comments on "Will the Gen 2 Volt Use the Spark EV Traction Motor Design?"

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Malcolm Scott

Staring into the photo your proposal seems reasonable to me. Cost is vitally important for the next Volt, so common parts is one way to do it. 105kW + whatever for MGA in a significantly lighter vehicle would make for quite spirited performance in EV mode. The larger capacity battery would be an enabler as well, even for GM’s conservative design philosophy when it comes to how the battery is used.

an_outsider

I alway admired the simplicity & efficiency of the electric drivetrain of the Spark EV.

http://insideevs.com/gm-general-says-spark-evs-400lb-ft-of-torque-no-misprint/ (from 0-2000rpm)

In my minds, that one was never designed for this specific car but probably was, kind of scale long term Beta test for this wonderful traction motor, before the introduction of the projected GM pure EV…

In brief, maybe they are closed parent form wound stator, AC permanent magnet rotor with the 2016MY Volt but I don’t believe being a carbon copy.

Now, image a Sonic size AWD version, front & rear traction motors, kind of city car version of the Tesla S P85D =)

Anon

Dual motor Sonic? Where would you put the batteries? What about cargo space? GM would pretty much need to design / switch to a skateboard platform, for any of that to be possible…

I just don’t see GM bothering to go to that effort at this time… Their next BEV will have all the usual shortcomings from converting a small ICE car, and simply electrifying it. Think Ford Focus EV. 😛

David Murray

Sorry, I’m not seeing it. The motor in the Volt will definitely NOT be the same motor in the Spark. Beyond the fact that we know the Volt’s transaxle will have TWO motors whereas the Spark has just one, we can pretty much say without a doubt that the two drivetrains are of a completely different design. About the only thing you could make a comparison to is some of the similarities in the design of the rotor/stator. But definitely NOT the same part.

DonC

I think GM has the solution for BEVs, which is a high torque motor and a single reduction gear. Very simple and complete.

Not really relevant for a hybrid, where efficiency seems to require two motors. I think the next generation drive train will be similar to what you find in the Prius and not directly related to what you find in the first generation Volt. The small motor/generator connected to the sun gear. The large motor/generator connected to the ring gear. And the engine connected to the planetary carrier.

Consequently you won’t get the four modes of the first generation plus a fifth mode. What you’ll get is five different modes. The “fifth” mode in this set up would have the carrier locked to the engine and the two motors providing torque through the sun and ring gears.

Bill Howland

Not much information here really. We were already told at least one of the two motors will be a synchronous Permanent Magnet design.

I’m not sure what the author is trying to tell us because I sure don’t get any information without actual gear ratios, frequency range of the inverter(s), peak output, etc.

Not even sure in 2 weeks time GM will release the info since they may say its ‘proprietary’ as was operation of the GEN 1 Volt.

Lad

You see; I’m one of those guys that buys a forever car and do my own maintenance; In fact, my truck is a very desirable MY 2000 Toyota Tacoma going on 15 years…they don’t make ’em in that size anymore. My Leaf is a 2011, #669, going on four.

I like “simple” and/or “uncomplicated” when it comes to cars. My pick for a new car would most definitely not be a hybrid, like the GM Volt, because they are engineering “busyboxes.” Drop all that complication and engineering experimentation and give me a plain old single electric motor BEV.

You buying a Volt, with a complicated IC engine,….a serial hybrid?…strongly consider a lease…otherwise you belong to the dealer.

pjwood

The 1.4ltr has been quoted as 1k-2k, assuming they ever do go bad with the few miles so many see. OTOH, the Leaf battery, now that you evidently can replace it, is >$5k. Even a battery as big as the Tesla’s doesn’t stop “the planning” associated with using a BEV. 60kwh, that much more so. Less than 30kwh, as the Leaf has, and it becomes essential to understand in what scenarios it isn’t an appropriate automobile. For that reason, I wouldn’t be quick to compare the Leaf to the Volt. People do, but I don’t see it.

Breezy

I do my own maintenance, but I’m not about to work on a transmission in any case. Even if I could do it the car couldn’t be out of commission for that long.

Toyota’s hybrids are some of the most reliable vehicles around, and the Volt has been doing fine so far. I hope it stays that way since I plan to own mine for another 8.5 years.What you

DonC

My Leaf is definitely simple … as in it simply sucks. LOL At this point the range of the Leaf isn’t too different than the electric range on the Volt. If you can ignore the unacceptable battery fade it’s reasonably reliable if built a tad cheaply. But seriously, who in their right mind can ignore a diminishing electric range.

Generally speaking, the whole “electric cars will have fewer problems” is just rubbish AFAIK. Cars have thousands of parts, most unrelated to the drive train, and any one of those can fail. The Model S is a pure BEV but is seems to have more problems than most ICE cars.

Less scheduled maintenance maybe, but even then it’s not a clear case. For example, the Volt needs an oil change every two years whereas the Leaf doesn’t. However the Leaf needs a brake flush every two years which the Volt doesn’t. Mostly a wash.

Bill Howland

“….My Leaf is definitely simple … as in it simply sucks. LOL At this point the range of the Leaf isn’t too different than the electric range on the Volt…..”

DonC, that is unbelievable Candor, and you’re to be seriously congratulated for admitting it. After all, what with the big money involved buying an electic car, admitting that there might be problems with it after spending all that money isn’t easy.

Are you saying that the Leaf you have is down to a 40-50 mile range? That’s just horrible.

My Volt, if driven gingerly, can get 40-50 miles per charge around town in the spring and fall, and that’s a ‘reduced range’ 2011.

pjwood

Food for thought. Nice thought process, George. I’m a big fan of GM’s modes, and think Tesla and BMW should think again. The P85D appears to be having big modal issues, with the two motors not entirely having been thought out, for efficiency. They aren’t clutched, but somehow digitally linked.

155kw would add some real authority to Volt’s already nice ~270ft lbs of torque.

Bill Howland

“…with the two motors not entirely having been thought out, for efficiency….”

I thought Elon Musk said the 4wd S could go more miles than the standard S? But then that statement was ‘revised’?

I’m curious because you are saying that the model S 4wd is not that efficient?

As a general rule of thumb, the Asynchronous ‘Tesla’ style motors used in all Teslas to date are not as efficient as the Synchronous motors used in other EV’s, but I’m not sure that is the point you are making.. Please clarify.

Foo

The white sticker on the front bumper still drives me crazy.