Author Topic: Teardown Reveals the Remarkable Complexity of Chevrolet's Volt  (Read 3218 times)

scott.fauque

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Teardown Reveals the Remarkable Complexity of Chevrolet's Volt - A look inside the car reveals just how complicated it is.
KEVIN BULLIS 04/20/2012
http://www.technologyreview.com/blog/energy/27785/

Sophisticated seems more appropriate.  It blends the technology of electric (motor, regen 'brakes', accelerator pedal) with mechanical (ICE/GG, brake pads, CVT|MODES) in a very smooth and elegant interwoven way.

"UBM Tech Insights took apart the car’s battery and charging system to identify the components of each, and it’s making at least some of its results, including photos, available for free here"
[here is a link where you can get these 3 presentation 'sent' to you via email links]:


paul.schlie

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Re: Teardown Reveals the Remarkable Complexity of Chevrolet's Volt
« Reply #1 on: April 23, 2012, 03:36:49 PM »
From the article:

"A complex transmission system also allows the gas engine to connect directly to the wheels. The new teardown looks at the electronics used to control this system. The charging and power distribution system is complex, having over 10 million lines of code and 100 microcontrollers."

Why in the name of God did they do that?!?!?!  One of the biggest selling points of a serial hybrid is the simplicity.  Engine powers generator.  Generator charges battery and/or powers motor.  Motor drives wheels or brakes wheels.  All electrical interconnections (reliable, cheap(ish), simple).  Leave it to GM to throw a complex transmission system in to mess it all up.

If I remember right, the Volt concept even had a "modular" engine bay, which was even better.  The "engine" could be a small gas engine, small turbo-diesel, fuel-cell, extended battery... even a team of hamsters on wheels (very green, but low power and they smell funny.  :-)   I figured I could pop a new mini-turbine in there in 10 years or so when they became commonplace to give the car another 20 years of life.  Instead the thing is saddled with a single option for an engine and it's tied into the system so tight it can't be removed without completely re-designing it.  What a joke.  A sad, sad, mind-numbingly stupid joke.

-- Paul

scott.fauque

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Re: Teardown Reveals the Remarkable Complexity of Chevrolet's Volt
« Reply #2 on: April 24, 2012, 05:35:56 AM »
It does not appear you have done much research or looked into the details.  It is a sophisticated production vehicle to appeal to the masses (not just EV hobbiest) and excel at efficiency in various circumstances from stop and go to highway speeds (70+) and handling mountains and deserts.  The car will go 100 MPH on battery power alone.  Other PHEVs stop at 62 MPH or hard acceleration and use the ICE.  Many people are also getting 40+ MPG @ 70 MPH when in Charge Sustaining (CS) mode (ie. using ICE/Gas_Generator).

See this 7 minute deepdive.  http://www.youtube.com/watch?v=IWSK8BR6LT8  
See this 9 minute deepdive variation: http://www.youtube.com/watch?v=an-VyIau-FM  There are several other videos as well.

A break down fairly simply info *four* modes...

http://www.designnews.com/article/511165-Electronics_Boost_Chevy_Volt_s_Efficiency.php

Electronics Boost Chevy Volt's Efficiency - The Chevy Volt is more than a green vehicle. It's a smart, seamless driving machine that in some cases exceeds the performance of gas-burning cars.
Charles J. Murray, Senior Technical Editor, Electronics -- Design News, November 16, 2010

<snip>
Voltec drive unit now has four basic modes of operation: electric driving (low- and high-speed); and extended range driving (low- and high-speed).

Here's a quick look at the four modes as described in the article [] are additions:

Quote
Electric Low-Speed [in Charge-Depleting (CD) mode]: The simplest and most well-known of the Volt's four modes, this calls for the vehicle to use the charge from its 435-lb lithium-ion battery pack to power a 111-kW ac traction motor. When the traction motor turns, it transmits power to a sun gear in a planetary gear set, which turns the drive axle. Volt owners are expected to make heavy use of this mode - many will drive the car to work and back, charge it at night, and never use a drop of gasoline in the process.

Electric High-Speed [in Charge-Depleting (CD) mode]: The Volt typically hits this mode at about 70 mph. Then, the supervisory controller splits the power between the large traction motor and a smaller 54-kW generator-motor (which is still operated by the battery). The planetary gear set blends the power from the two motors and sends it to the drive axle. Even as it switches to this mode, however, the Volt still isn't employing its internal combustion engine - and therefore still isn't burning any gasoline.

Extended Range Low-Speed [in Charge-Sustaining (CS) mode]: When the battery's charge drops to an unacceptable level, the 1.4-â„“ I-4 engine makes its debut. At low speeds, the engine spins the generator-motor, which replenishes the battery.

Extended Range High-Speed [in Charge-Sustaining (CS) mode]: This is the most complicated and controversial (see sidebar) of the Volt's four modes. With the battery depleted at higher speeds (70+ mph), the controller opts for a power split. It calls for power to be delivered through the big traction motor and through the smaller generator-motor. Unlike the other modes, however, this one calls for the generator-motor to transmit power directly into a ring gear in the vehicle's planetary gear set. GM says it has a good reason for doing this - electric motor efficiency typically plummets at higher speeds. "You're bringing down the speed of the main traction motor and supplementing it with the generator-motor," a GM spokesman says. "As a result, you're improving the efficiency."
<snip>
Sidebar:
Quote
So is it an EV? Or a hybrid? To be sure, there's no direct connection between the gasoline-burning engine and the Volt's planetary gear set. Rather, the engine delivers power to the vehicle's generator-motor, which relays it to the ring gear of the planetary gear set. The bottom line is it's not a direct mechanical connection in the manner of a conventional gas-burning car, but the generator-motor arrangement is similar to that of a Toyota Prius, which is a true hybrid.

Still, GM insists the Volt should still be considered an EV. "It's clearly an electric vehicle," says Pamela Fletcher, global chief engineer for the Volt and for GM's plug-in hybrid electric powertrains. "You can accelerate from a stop to 100 mph and have the engine never come on. You could take the internal combustion engine out of it, and it would drive just fine. But if you took the battery out, it wouldn't drive."

Another excellent article with pictures.:
Chevy Volt Delivers Novel Two-Motor, Four-Mode Extended Range Electric Drive System; Seamless Driver Experience Plus Efficiency
http://www.greencarcongress.com/2010/10/chevy-volt-delivers-novel-two-motor-four-mode-extended-range-electric-drive-system-seamless-driver-e.html
« Last Edit: April 24, 2012, 05:39:26 AM by scott.fauque »

paul.schlie

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Re: Teardown Reveals the Remarkable Complexity of Chevrolet's Volt
« Reply #3 on: April 24, 2012, 03:44:19 PM »
I am impressed with the result.  Using the planetary gear system that way is similar to an idea I have.  But I still think it is an overly complex execution of a simple concept.

One of the comments to the article expresses my feelings perfectly:

Quote
It seems like they lost track of some design goals somewhere and increased complexity in many cases even where it was not needed.

" This configuration reduces battery drain at steady state, cruising speeds in a window ranging from around 30 mph to more than 70 mph (48 to 113 km/h), adding up to two miles (3.2 km) of additional all-electric range. "

OR...they could have used another .5kWh of the battery pack and gotten another 2 miles of range without adding all the cost/complexity.

Designing these types of systems requires engineers to make judgement calls and tradeoffs. It seems like whoever was leading this team was erring on the side of trying to squeeze every little ounce out of the system and may have ended up making the system itself too complex and missed the mark.

Impressive...but did it have to be?

Posted by: DaveD | October 20, 2010 at 05:50 AM

The original VW Beetle didn't have such a major impact because it of the efficient performance, it was the efficient design: Simple, easy to maintain, and inexpensive (i.e. less environmental impact to build).

I've heard some environmentalists say that the lowest environmental impact choice for a car is to re-build an older car instead of buying a new one.  Not keep an old smog-hog running, but update it with modern components where possible.  I feel electric car enthusiasts would be better served by a basic, simple design that could be mass produced quickly and widely.  If a major auto company like GM produces the electric car version of the VW Beetle they will sell and all of the laughing would die away quickly as the public got past the unfamiliarity and novelty and realized how practical they are.

Get it out the door with a basic battery, or better yet have battery options.  A modular system would allow that.  A simple software update to a universal charging system would allow it to support any battery pack.  In 5 or 10 years when the next generation batteries appear people will be able to upgrade and double or triple their range.  The simple, efficient design of the base platform means that it will last a lot longer than typical.  Over the total life of the car it will end up having significantly less environmental impact than a more fancy car with 20% better efficiency.

Total cost of ownership is what is killing the hybrids now.  The systems are so complex they add too much to the cost of the vehicle and owners can't recoup the cost, even with $4 gas.  Why hasn't the flywheel/starter/alternator on every car's engine been replaced with relatively low-power motor/generator like Dynastart?  I've heard that in quantity the cost is comparable.  Add just a little battery or ultra-capacitor storage and any car could gain 5% efficiency or more for almost no cost.