OT Chevy Volt

3KW is not a requirement, it shows how completely inadequate a portable generator is for the task.

Logical analysis isn't one of your strong points, is it?

jsw

I don't have the figures for the vehicle in front of me.

KMA,H.

-- Courage and perseverance have a magical talisman, before which difficulties disappear and obstacles vanish into air. -- John Quincy Adams

Well, yeah, the idea behind the car design is that you'd use electricity for daily commuting, shopping at the local mall etc, but if you needed to go on a long trip (or if you failed to charge) you'd be able to use the same car, but in gasoline mode, so you can fill up in 3.5 minutes including pee break.

Makes perfect sense, since most of us drive most of our miles/klicks in a fairly small radius, but want the ability to go further occasionally (and we also worry about running out of charge).

At a higher level, there is a big issue with renewable energy in that storage (for when the wind isn't blowing or the sun isn't shining on the panels) is expensive. One could imagine, say, 100,000,000 cars plugged into the grid, and allowed to feed back, say, 20% of their charge into the grid overnight (the owner would be paid back for that energy and that service). Then, during the day, the cars could charge, say with solar, and the owner would be billed for the net.

No. No one would drive 270 miles, then stop and recharge the battery, and count the recharge time as "trip time." Conversely, if you charged the battery before your trip, no one but a moron would count that charge time as "trip time." The whole thing is baloney.

If you had to go more than 270 miles you would simply re-fill the gas tank. Battery charging time doesn't enter into it.

Yeah. The viability of all of the electric-only and plug-in hybrid cars is based on certain patterns of use. For the all-electic, it's nothing but short hauls. At their present state of development, the plug-ins are based on a large portion of short hauls.

As it has been for 100 years, the limitiation of any of the electric configurations that run at least part of the time on electricity only is the batteries. The Volt, as I said, may be a bit ahead of its time. But the configuration and the expected use patterns are perfectly viable. They're just not *yet* cost-effective, for all but a limited number of drivers.

Those ideas are over my head. I read a paper or an article on using cars as storage for the grid, but there are so many variables that I haven't attempted to evaluate it.

Whoops, you're right!

Jon

No, I don't believe the Volt is a serial hybrid. What I understand, entirely by reading articles on it, so that could be wrong, is that it is a dual-mode vehicle. it runs off batteries until they are low, then runs off the engine, but never allows the batteries to be charged by the engine. Maybe the batteries can take charge when decelerating. But, my understanding is once it has switched to engine power, is will not behave as other hybrids.

Agreed!

Exactly! if the Volt allowed the battery system to stay operational and used it like other hybrids, they could have cut the size of the gas engine considerably. But, then they would have needed to make an engine specific to the Volt, which they SHOULD have done! Cutting weight has huge benefits.

The Honda Civic hybrid has only a 20 Hp assist motor, so it NEEDS a fairly hefty engine. The Prius and Volt have enough electric motor HP to use it as the primary drive.

Well, mostly true, but there is no way for the serial scheme to beat a parallel hybrid for low energy loss. Coupling a gas engine to the wheels with a geared or CVT transmission has to be more efficient that going from crankshaft to generator to VFD to VFD to motor to transmission to wheels. Now, if you optimize the engine for ultra-efficiency and it becomes problematic to directly drive the wheels with it, then it may work out better.

Jon

You certainly don't need 86 HP for an air conditioner. Both the Prius and Honda Civic hybrid have electric air conditioning that runs off the hybrid battery. 3 - 5 engine Hp is all it takes if running off the engine. I assume the Volt also has to have electric A/C.

Jon

Ha! All of Chevy's press releases described the car as a pure series (or serial) hybrid:

Now I see that it's a hybrid hybrid -- maybe. :

On this one, scroll down to the GM press release. Some of the news reports have said that the "second motor" is the electric generator. Others say it's the gas engine. It appears to me, from Motor Trend's analysis, that they're talking about the gas engine:

I realize that's a little hard to follow, but note that the batteries ARE charged by the engine. The engine drives the wheels mechanically only in a very limited realm. You'll note that one of the electric motors is a generator that charges the battery.

Most of the time, the car runs as a serial hybrid, with the gas engine (if it's running) charging the battery, and the battery powering the electric motor that drives the car. Under some conditions, the gas engine is clutched mechanically to the planetary gearset and contributes to the drive power.

But the Volt's gas engine is only 1.4L, 80 hp. The Prius engine is

1.8L, 98 hp. The Honda Civic Hybrid's engine is 1.5L, 110 hp.

I haven't seen the weight figures on the engines, but the Volt's engine is the smallest of the three in displacement. It's based on the little Opel engine they sell in Europe.

Take a look at

for an interesting application. I know this guy. He's kind of a kook, and not the nicest guy top work for (I know a few of his ex-employees), but you have to admit, it's a cool idea, and he's been doing it for years.

Well, this is totally new info, everything I've read so far says there's no mechanical connection in the Volt!

But, quoting from the article : There is no direct mechanical connection (fixed gear ratio) between the Volt?s extended-range 1.4L engine and the drive wheels.

Jon

Yabbut....if you read all of that stuff (only recommended if you're obsessive, like me), you'll see that the article was sort of fudging. It appears to me from the entirety of those press releases and articles that the gas engine is clutched to one part of the planetary gearset at some range of torque loads (one Chevy engineer says it's torque, not road speed, that determines when it hooks up) and adds approximately 10% of the total power delivered by the wheels.

Basically, it's a series hybrid setup with a complex coupling between the primary motor, the secondary motor/generator, and the gas engine. And the coupling looks like it's handled through clutching and unclutching the planet-gear yoke and the ring gear. In several places it says that the gas engine alone will not drive the wheels. That sounds to me like the planetary gear set will freewheel if the main electric motor isn't driving it with some force. In fact, I think that's the explanation those writers were reaching for. As the once-upon-a-time gear editor for American Machinist, I feel planetary gearsets in my bones.

Jeez. Did they have to do that to us? I never would have made a comment here if I had known what was going on there. d8-)

Anyway, the Volt is one more step on the path to somewhere. I still think it's ahead of its time, and that the only people who will buy them are the early adopters who want to be first on their block with something new.

Very interesting. I had heard something about this, but I never looked into it. It sounds like a really good idea for someone like me, who has no desire and little need for a generator.

But I don't have a lot of desire for a Prius, either. Maybe a Leaf or Leaf-like object as our second car, if my wife continues to work one mile away and I continue to work at home.

Excellent discussion on the design details, thanks.

I can see this design violates the first rule of excellent design: KISS

Of course, battery technology is the problem. Trying to make this idea work with an insufficient battery complicates the hell out of it.

Karl

Just taking a SWAG here, I suspect that when both the gas engine and the electric motor drive the planetary gears, the electric motor might make up the speed difference between the gas engine and the road wheels, gaining some of the benefit of a CVT from a single ratio transmission.

???

Yeah, I think you've put your finger on the bottom line.

And that explains why there is so much battery research going on, much of it government sponsored. It also explains, at least in part, why China was (and is) so hell-bent on controlling Tibet, home of the world's largest lithium reserves.

That's an interesting thought. Without a better description from Chevy's engineers, I can't identify exactly what is happening.

One of the engineers pointed out that the large majority of power always comes from the electric motor, and that the gas engine cuts out at something like 6,000 rpm.

I'd like to know how the gas engine is clutched to the planetary gears. I think that would explain most of it.

No, but if you're running at 70mph on a rainy night with headlights, the a/c dehumidifying the windshield, -and- the radio blasting out of ten speakers at 130dB, you need more generating power for the accessories.

I wish my Tundra had come with a hybrid option and a 3L inline 4. At least half of my trips are in town and less than 12mi total. The littler (4.7L) V-8 has way too much power most of the time, since I'm not pulling a 10k# load.

-- Courage and perseverance have a magical talisman, before which difficulties disappear and obstacles vanish into air. -- John Quincy Adams