REEV concerns

[Joseph]

Just compare the titles of the two articles.

Elon response summed up all the difficulties of REEVs well, sweet and simple.

 

[vfx]

Ya know, I read that this morning from GM-Volt.com. I preferred the version without all the editorializing.

Tesla CEO Critical of the Chevy Volt | GM-VOLT : Chevy Volt Electric Car Site

But those commenters have a few things to say...

edit to add

Oh Looky at number 71... KB is alive and piling on Elon

kent beuchert Says:
April 6th, 2009 at 9:43 am

 

[doug]

2011 Chevrolet Volt First Drive - Car News/Green Machines/Car Shopping/Hot Lists/Reviews/Car and Driver - Car And Driver
via
What Will the Volt’s Generator Mode Feel Like? | GM-VOLT : Chevy Volt Electric Car Site

What isn’t yet clear is how the Volt will behave when the battery is depleted and the gasoline engine kicks on to provide more juice. In this so-called range-extending mode, the electric motor will be limited to the power provided by the 1.4-liter four-cylinder engine under the hood. The gas engine is never used to charge the battery; the engine turns a generator that directly feeds power to the electric motor. If the engine is revving at 2000 rpm and making 25 hp, the electric motor will only be able to make 25 hp. If more power is needed, the gasoline engine could conceivably run at its power peak at a very high rpm. Taking the point further, if the gas engine is only rated for 100 hp (our estimate of its power output), the 149-hp electric motor will only be able to make 100 hp. The upshot: the Volt will be quicker running on battery power than it will be when the gas engine is providing the electricity.

Unable to try the gas-fired solution for ourselves, we asked Posawatz how the experience will change when the battery is discharged and the gas engine kicks on. “The work being done by the development guys as we speak is to create a gentle feathering of engine rpm,” he said. “So you don’t even notice that the engine kicks in. And to try to operate at the right points and to transition the rpm points depending on the load you’re getting—to behave like someone would want it to behave. You may get into a position under an extreme grade or hill climb, where the engine rpm will be pretty loud—running pretty hard. At a certain point in time that rpm will be relatively unpleasant. This is the challenge of different road loads: how can we keep the NVH reasonable for a customer?”

 

[ChargeIt!]

I am (again) getting more disappointed in the Volt.

I had been under the impression until now that the gas engine charges the battery for use by the electric motor. Now this !

How complicated can you get ? (Leave it to GM to proving that ! )

 

[efusco]

The gas engine is never used to charge the battery; the engine turns a generator that directly feeds power to the electric motor. If the engine is revving at 2000 rpm and making 25 hp, the electric motor will only be able to make 25 hp. If more power is needed, the gasoline engine could conceivably run at its power peak at a very high rpm. Taking the point further, if the gas engine is only rated for 100 hp (our estimate of its power output), the 149-hp electric motor will only be able to make 100 hp. The upshot: the Volt will be quicker running on battery power than it will be when the gas engine is providing the electricity.

That just doesn't sound believable. I have to assume they're mistaken. That certainly isn't the original concept released and just doesn't seem to make sense...why run the ICE like that where it's RPM bounces around depending upon load and thus rarely in it's most efficient range.

It makes so much more sense and is conceptually more logical to run it always in a very high efficiency rpm range to charge the battery...unless they're afraid it wouldn't be able to sustain the battery SOC at times and had to change the design concept. And if that's the case, they could be on their way to failure of this concept...IMO.

 

[graham]

It sounds to me that one of their design considerations was trying to reduce the engine noise. So instead of running the engine full-tilt, they run it pretty slowly (quietly) unless the drain on the battery is so high that they have to run the engine at full tilt (along with its engine noise and gas usage). If they can reduce the engine to running only at bare minimum, they will have a quieter car and can claim higher gas milage over short trips.

 

[TEG]

It also sounds like (unfortunately) people don't like the ICE to have a mind of its' own. They want the ICE RPMs to correlate to pedal position to some degree. So if you aren't accelerating, people don't want the ICE to start revving too much. Again this works against the idea of only running the ICE at most efficient RPM, and the idea of having it come on to charge batteries then shut down again once it has enough charge. Basically people want what they are used to, and so it sounds like these series hybrids are being designed to act as an EV for a while, then act as if the ICE is connected to the wheels in some way even though it isn't.

 

[Kevin Harney]

I never thought of that until you said it. But I can tell you I would be a little bit concerned if my car was always at a high speed idle even if my foot was off the gas. That would be disconcerting until you got used to it. No focus group would really have time to get used to it.

 

[vfx]

Not to mention how hard it's going to be to settle on an equitable number representing MPG (or GMP).

 

[Kevin Harney]

It should be some form of energy storage like joules / mile or what ever is the best value other than joule. All energies should be converted at that rate. Amount of energy in a gallon or in a Kwh or in H2 or whatever.... center us on ENERGY used not anything else.

 

[doug]

Exclusive: The Engineering Challenges of Volt Generator Mode | GM-VOLT : Chevy Volt Electric Car Site

 

[vfx]

Wow, Tough calls to make.

For some they will make some big mistakes in what decisions are ultimately made, just like Tesla.

For them it's even more dammed if you do, dammed if you don't.

 

[Tdave]

They're putting way too much emphasis on "what the driver expects". This is a new paradigm. Time to reinvent what the driver expects. Just do what's best for efficiency and/or performance.

 

[doug]

Will the Volt Have Power Limitations on the Highway? | GM-VOLT : Chevy Volt Electric Car Site

 

[vfx]

Will the Volt Have Power Limitations on the Highway? | GM-VOLT : Chevy Volt Electric Car Site

Finally they come clean. I mean it's fine that the car can't do everything. No car can. Sometimes these guys should just say what the design intent is and then target those buyers.

*****************
Doug's at 3000 Posts!

 

[TEG]

If you started on a drive from SF to Tahoe and flipped the "try to keep my battery at least 80% full" switch as you left, then the ICE would come on sooner, and you would start uphill past Sacramento with plenty of charge to 'make the grade' uphill without problem. The possible problem (as I see it) is the weak ICE coupled to a strategy of "drain the pack first" with no option to override.

Another option would be to have it GPS/Nav coupled and it calculates what you need based on the destination you programmed in at the start of your trip.

Yep:
GM Volt will offer 'Mountain Mode' for hill climb charge preservation...

...under a "limited set of circumstances," on a handful of known grades in the country, vehicle performance "may be degraded" under sustained heavy loads when the engine providing electric power to drive the car. The Mountain Mode option helps compensate for this in some circumstances. While drivers may not be used to planning ahead, future navigation systems might suggest that the special mode be triggered if it knew that a preset route included a long uphill stretch.