GM Chevy Volt

[scaesare]

The Volt can run in serial or parallel hybrid mode. It is capable of both and uses both to maximize efficiency.

This. There are scenarios where the gas engone provides torque directly to the drivetrain, (aka parallel). There are also times when it acts a series hybrid.

When GM originally announced the Volt, they claimed it sould be a series hybrid only. They changed this quietly, but confusion persists.

I am not passing any judgement in this post on if this is good or bad. I am merely pointing out it is inaccurate to claim the ICE never directly provides locomotive force directly to the drivetrain. It does.

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It cannot run in parallel mode. That would require a direct mechanical link between the ICE and the wheels, which the Voltec drivetrain can't do.

Untrue.

See: Volt Drivetrain

 

[rabar10]

Mod note:

A bunch of posts got shoveled, again, over to the Pure BEV Dogma thread. And, because lots of posts were quoting other posts that got moved, they got moved too -- probably more than was ideal. Apologies if yours got caught up in it.

I did leave some of the posts discussing the details of the Volt's drivetrain here, for reference, since it is admittedly complex and confusing.

 

[brianman]

I did leave some of the posts discussing the details of the Volt's drivetrain here, for reference, since it is admittedly complex and confusing.

Suggestion:
I'd love to see the Prius, Volt, Karma, Leaf, etc. enthusiasts on the forum create a blog post for each of the various plug-in vehicles detailing what we (think we) know about the drivetrain. It would be very useful for education myself and others in a more direct fashion that skimming a mixture of content across threads.

 

[Jeff N]

It actually can, but to be fair, only under very specific circumstances. Something like at speeds over 70 MPH and the battery pack depleted.

No, that is quite misleading information that floats around the media and Internets. It's a zombie meme that's hard to stop.

The Volt frequently (majority of the time) runs in a series/parallel mode similar to how the Prius works (but different in some details) at speeds above 35-40 mph at lighter torque loads (mild acceleration on flat roads or less) and at higher torque as vehicle speeds go up. At speeds below 35 mph the Volt operates in series mode with the engine and generator un-clutched from the planetary ring gear.

The "infrequent" and "70 mph" thing was due to confused early media reporting that keeps replicating itself. It comes from an explanatory video shown to journalists that used 70 mph as a typical speed at which the Volt is almost always in its parallel configuration but unless you are flooring the "go" pedal it will have actually switched at a far lower speed.

Many people instinctually want to think that the Volt switches to its parallel mode under hard acceleration but actually that is when it really wants to switch to series mode and use it's electric motor only (with the gas engine just generating electricity together with power from the battery). Of course, the gas engine never starts up due to torque demand or vehicle speed -- that's GM's definition of an EREV. The gas engine is only in the picture when it is already running for other reasons (like an "empty" battery).

Specifically, under the US06 EPA highway test cycle, the Volt spends 58% with the gas engine mechanically connected, 16% in series mode with gas engine, 21% with engine off and using one electric motor, and 5% with engine off and using the two electric motors combined. In other words, it spends only 16% of the time in series mode with the gas engine turning the generator just making electricity.

US06 includes a bunch of starts and stops at the beginning and end of the test cycle which accounts for the time spent without the gas engine mechanically connected. The older, less aggressive, and freer-flowing HWFET highway cycle almost certainly spends even more time with the gas engine coupled although I haven't seen the numbers.

See this and the post following it for some graphs and textual descriptions which are based on an SAE technical paper written by the GM engineers that designed the Volt transmission:

CS mode thread at GM-Volt forum

 

[thelastdeadmouse]

I can't say I understand the obsession with what the Volt is called and the hate it gets because the engine sometimes connects to the wheels directly. They could have easily made it so the engine is only a generator, but they put in the extra time and expense of making the vehicle as efficient as they could which should be commended, not condemned.

It really doesn't have to be as complicated as some people make it, I can explain everything you need to know about the Volt powertrain modes in two simple sentences:

When it has power in the battery its an EV, and when it doesn't its a hybrid. When its a hybrid sometimes the engine is just a generator and sometimes it powers the wheels directly, whichever is more efficient at the time.

 

[JRP3]

I can't understand why people consider an accurate description of a vehicle as "hate". The Volt's hybrid nature has nothing to do with the status of it's battery, it has to do with it's design and construction. It's always a hybrid. Sometimes it operates from power stored in the battery, sometimes it operates from power stored in the gas tank, but it always has both systems on board, which is why people bought it.

 

[Jeff N]

My comments here:

Pure BEV Dogma - Page 69

 

[Larry Chanin]

I can't say I understand the obsession with what the Volt is called and the hate it gets because the engine sometimes connects to the wheels directly. They could have easily made it so the engine is only a generator, but they put in the extra time and expense of making the vehicle as efficient as they could which should be commended, not condemned.

It really doesn't have to be as complicated as some people make it, I can explain everything you need to know about the Volt powertrain modes in two simple sentences:

When it has power in the battery its an EV, and when it doesn't its a hybrid. When its a hybrid sometimes the engine is just a generator and sometimes it powers the wheels directly, whichever is more efficient at the time.

Very nice simple summary. I think that the Volt is a great hybrid that will assist in the transition to battery electric vehicles.

Because its nevertheless still a hybrid I would say that when it has power in the battery its more accurate to say that its an EV dragging around an idle internal combustion engine, gas tank and exhaust system. :wink:

Larry

 

[rolosrevenge]

I think the Volt is a wonderful car and a very efficient PHEV. As an electrical engineer who specializes in EVs, I can't stand stupid meaningless marketing terms like EREV.

 

[dsm363]

I can't say I understand the obsession with what the Volt is called and the hate it gets because the engine sometimes connects to the wheels directly. They could have easily made it so the engine is only a generator, but they put in the extra time and expense of making the vehicle as efficient as they could which should be commended, not condemned.

It really doesn't have to be as complicated as some people make it, I can explain everything you need to know about the Volt powertrain modes in two simple sentences:

When it has power in the battery its an EV, and when it doesn't its a hybrid. When its a hybrid sometimes the engine is just a generator and sometimes it powers the wheels directly, whichever is more efficient at the time.

Exactly. Perfect summary. It acts as a BEV until it runs out then it is a hybrid. Pretty simple.

 

[Larry Chanin]

It acts as a BEV until it runs out then it is a hybrid.

Isn't that true of all hybrids? :biggrin:

Larry

 

[Jeff N]

Because its nevertheless still a hybrid I would say that when it has power in the battery its more accurate to say that its an EV dragging around an idle internal combustion engine, gas tank and exhaust system. :wink:

Much like a Model S drags around a large, heavy, and expensive battery pack that is far in excess of what a typical owner uses on their typical daily drive. Nevertheless, I want my future 3rd gen Tesla to have an optional 250+ mile battery pack so it is there for my convenience when I need it.

 

[richkae]

When it has power in the battery its an EV, and when it doesn't its a hybrid. When its a hybrid sometimes the engine is just a generator and sometimes it powers the wheels directly, whichever is more efficient at the time.

Agreed. This is also an excellent description of my old Prius.

 

[Jeff N]

Agreed. This is also an excellent description of my old Prius.

No, this would be a rather inept description of your Prius because your Prius would have typically switched to hybrid mode when you accelerated too fast or drove over 40-something mph even though it's battery still had usable charge remaining.

 

[richkae]

No, this would be a rather inept description of your Prius because your Prius would have typically switched to hybrid mode when you accelerated too fast or drove over 40-something mph even though it's battery still had usable charge remaining.

I stand corrected. I'll remember to add that asterisk.

 

[Topspin]

No, this would be a rather inept description of your Prius because your Prius would have typically switched to hybrid mode when you accelerated too fast or drove over 40-something mph even though it's battery still had usable charge remaining.

If people are that upset about there electric def, when the bubble pops in the stock they will really be shook up

 

[scaesare]

I think the Volt is a wonderful car and a very efficient PHEV. As an electrical engineer who specializes in EVs, I can't stand stupid meaningless marketing terms like EREV.

Indeed.

The Volt is a hybrid. It has some different modes of operation. Nonetheless it combines two distinct power sources to provide locomotive force.

It's a fine car. People shouldn't confuse not buying in to what feels like a "marketecture" term from the company with criticism of the platform.

 

[dsm363]

Indeed.

The Volt is a hybrid. It has some different modes of operation. Nonetheless it combines two distinct power sources to provide locomotive force.

It's a fine car. People shouldn't confuse not buying in to what feels like a "marketecture" term from the company with criticism of the platform.

Exactly. The Volt is the only affordable car with decent EV only range and easy 5 min refueling. It's still a hybrid though and nothing wrong with that.

 

[Topspin]

Exactly. The Volt is the only affordable car with decent EV only range and easy 5 min refueling. It's still a hybrid though and nothing wrong with that.

Bloggers who track ev sales call it electric so do the manufacturer

 

[ItsNotAboutTheMoney]

Bloggers who track ev sales call it electric so do the manufacturer

InsideEVs.com calls it a Monthly Plug-In Sales Scorecard. Differentiation matters more to individuals than industry analysts.