Pure BEV Dogma

[scaesare]

I'd say this thread has plenty of evidence of confusion regarding the Volt. Talking to the general public about the Volt also reveals much confusion about the vehicle.

Indeed. A buddy has a Volt (2 of them actually), and when I got my Tesla, we started talking about the platforms. I had to convince him via teardown diagrams and articles that the ICE actually provided locomotive force to the wheel mechanically in some situations.

He had been adamant that it didn't prior to that... and he owns a custom car shop.

Much confusion indeed abounds, and it's unfortunate that GM seems to be a significant contributor to it.

 

[stopcrazypp]

Don't you think it's reasonable to consider the mode of propulsion, but not climate control? If I put a wood stove in my EV for heat it's still an EV because the propulsion is electric only, and can only be electric.

That's how SAE defines it too. Accessories are not included because it leads to questions of how to deal with ICE cars (where a battery supplies accessory power). Therefore, a EV with non-battery based heating is still considered a pure EV by SAE terminology. Propulsion is what matters.

I will concede to Jeff that the PiP won't meet the CARB/GM definition of EREV, since CARB/GM defines EREV by the capability to travel at "highway" speeds. The PiP has a top EV-only speed of 62 mph, just barely under the typical 65mph speed limit of most California/US highways. Although, if you take highway speeds to mean between 55-70mph, the PiP still falls within that range.

 

[mknox]

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.

That's because you think like an engineer :wink: I think EREV makes a lot of marketing sense for the layperson. To most people, if it's got a plug it's "electric" and the concept of having a range extending engine is an easy concept for people to understand. (To me, it sounds "better" than Toyota's "Hybrid Synergy Drive").

 

[scaesare]

That's because you think like an engineer :wink: I think EREV makes a lot of marketing sense for the layperson. To most people, if it's got a plug it's "electric" and the concept of having a range extending engine is an easy concept for people to understand. (To me, it sounds "better" than Toyota's "Hybrid Synergy Drive").

The problem I have with the EREV moniker is that it attempts to suggest the idea that the ICE/generator combo is there simply to extend the range of a vehicle that otherwise would operate in every bit the same way, albeit with lesser range.

However that is untrue. There are modes where the ICE provides capability that the EV modes alone cannot.

This is fine, and a perfectly legitimate (and smart, IMO) use of the ICE aboard the vehicle, but it feels disingenuous to classify it as an EV when there are hybrid modes of operation.

 

[thelastdeadmouse]

The problem I have with the EREV moniker is that it attempts to suggest the idea that the ICE/generator combo is there simply to extend the range of a vehicle that otherwise would operate in every bit the same way, albeit with lesser range.

However that is untrue. There are modes where the ICE provides capability that the EV modes alone cannot.

This is fine, and a perfectly legitimate (and smart, IMO) use of the ICE aboard the vehicle, but it feels disingenuous to classify it as an EV when there are hybrid modes of operation.

This is not true of the Volt. There is no circumstance where the engine running provides more performance / capability other than additional range. The car in fact drives slightly better in electric mode in my experience.

 

[dsm363]

This is not true of the Volt. There is no circumstance where the engine running provides more performance / capability other than additional range. The car in fact drives slightly better in electric mode in my experience.

I thought they did have the engine directly drive the wheels under rare circumstances because it was more efficient in those situations.

 

[thelastdeadmouse]

I thought they did have the engine directly drive the wheels under rare circumstances because it was more efficient in those situations.

Only once the battery is depleted. While there is juice in the battery you'll get the car's maximum performance from the electric drive train alone. The engine will only ever turn on once the battery is depleted or is the driver turns it on themself.

 

[Doug_G]

I thought they did have the engine directly drive the wheels under rare circumstances because it was more efficient in those situations.

The circumstances aren't that rare, but yes.

 

[scaesare]

This is not true of the Volt. There is no circumstance where the engine running provides more performance / capability other than additional range. The car in fact drives slightly better in electric mode in my experience.

There are some modes where the total power delivered to the wheels is greater with the ICE engaged than with not. Manually engaging "mountain mode" can demonstrate this.

 

[thelastdeadmouse]

There are some modes where the total power delivered to the wheels is greater with the ICE engaged than with not. Manually engaging "mountain mode" can demonstrate this.

I'm fairly confident that all mountain mode does it attempt to refill the battery to 50% or maintain it at 50%, so if you have a situation where you need to climb a mountain while in range extended mode, the battery can supply addition power because the gasoline engine does not have the performance to do it alone, not the other way around. That being said, I've never had any use for the mountain mode myself, and will certainly be willing to concede the point if provided with evidence to the contrary.

 

[ItsNotAboutTheMoney]

The problem I have with the EREV moniker is that it attempts to suggest the idea that the ICE/generator combo is there simply to extend the range of a vehicle that otherwise would operate in every bit the same way, albeit with lesser range.

However that is untrue. There are modes where the ICE provides capability that the EV modes alone cannot.

This is fine, and a perfectly legitimate (and smart, IMO) use of the ICE aboard the vehicle, but it feels disingenuous to classify it as an EV when there are hybrid modes of operation.

I think you have it backwards: if you have an engine anyway and you gain more from parallel* hybrid modes of operation than you lose from not having purely serial, it makes sense to add the capability. But the Volt does not, by default, use the engine for traction unless (a) the battery has run down to CS mode (b) the engine is being run by the car in a maintenance mode. To me it feels inaccurate to insist on lumping it in with other PHEVs that have normal operation that's fundamentally different. I only don't call it an EREV because it can't handle the heating problem that BEVs do, so I would prefer a Full prefix (FPHEV) that emphasizes that it has full capability in EV mode, which is a major separator. (And note that Full to me doesn't mean that it can't have more power with hybridization, but that the car can, will by default and is expected to driven up to and at all legal speeds purely in EV mode without a noticeable compromise on performance that would make it underperform compared to a typical vehicle.) Otherwise, let's just have a single acronym, V for Vehicle and call it good. And I certainly don't have any problem with referring to the Volt as an EV.

- - - Updated - - -

I'm fairly confident that all mountain mode does it attempt to refill the battery to 50% or maintain it at 50%, so if you have a situation where you need to climb a mountain while in range extended mode, the battery can supply addition power because the gasoline engine does not have the performance to do it alone, not the other way around. That being said, I've never had any use for the mountain mode myself, and will certainly be willing to concede the point if provided with evidence to the contrary.

Correct. MM effectively raises the expected and top CS mode percentages so that there's more battery available to the (underpowered) engine.

We live in a hilly area, not a mountainous one, so we have never needed it.

 

[Doug_G]

To me it doesn't matter whether it's a serial or parallel hybrid or both (it's both). GM did what was most efficient, and that is entirely appropriate. Why would we want them to design a car that is less efficient than it could be?

The Volt is clearly a plug-in hybrid electric vehicle, or PHEV. That's great - it's a decent bridge technology to pure EV. Their marketing division can call it EREV if they like, but that's really just another word for PHEV with some arcane technical details to make the distinction. What matters to drivers is the full electric range, fuel economy, and performance - what the car does, not how the parts are connected internally or what their marketing people call it.

 

[scaesare]

I'm fairly confident that all mountain mode does it attempt to refill the battery to 50% or maintain it at 50%, so if you have a situation where you need to climb a mountain while in range extended mode, the battery can supply addition power because the gasoline engine does not have the performance to do it alone, not the other way around. That being said, I've never had any use for the mountain mode myself, and will certainly be willing to concede the point if provided with evidence to the contrary.

From MotorTrend:

?..the Volt will flash a dash message “low propulsion power” when going up steep grades in extended range mode and will drop to 40 MPH. This will not happen if mountain mode is engaged , which will leave extra energy in the battery, causing the engine to go on sooner.

My point remains... there is more than simply range added. The car's performance characteristics are different, some of which is due to the mechanical engagement of the ICE.

 

[mknox]

What matters to drivers is the full electric range, fuel economy, and performance - what the car does, not how the parts are connected internally or what their marketing people call it.

That's kinda what I'm saying... but to the layperson, if it has a plug, it's electric and if it has an ICE and a plug, it's a range-extended electric. "Hybrid" seems to the layperson to be reserved to those that don't have a plug but do have an electric assist. I realize that technically this is not accurate...

 

[Duckjybe]

I thought they did have the engine directly drive the wheels under rare circumstances because it was more efficient in those situations.

I have a a Volt and was consciously monitoring the battery/engine use screen for this on my drive home last night. It seems that only under hard acceleration and only when the battery is depleted will the ICE drive the wheels directly as indicated by the power flow screen showing Battery and Engine use at the same time. The only other times the engine will come on are if you put it in Mountain mode or if it is extremely cold out and the cabin needs additional heating for a short time. Outside of these modes I have never experienced the ICE running when the battery has charge.

When its charged the Volt drives and feels just like an electric vehicle. I was doing 140km/hr no problem on battery. Try doing this in a traditional "Hybrid".

 

[thelastdeadmouse]

From MotorTrend:

?..the Volt will flash a dash message “low propulsion power” when going up steep grades in extended range mode and will drop to 40 MPH. This will not happen if mountain mode is engaged , which will leave extra energy in the battery, causing the engine to go on sooner.

My point remains... there is more than simply range added. The car's performance characteristics are different, some of which is due to the mechanical engagement of the ICE.

I think we're interpreting this differently. What MotorTrend is saying is that if the battery is already depleted and is running on the gas engine, which has lower power output than the battery, you'll get low propulsion power when climbing steep grades. On the other hand, if you engage mountain mode before you get to the mountain, the car will reserve some power in the battery to supliment the engine power when going up steep grades. The battery can be used to enhance the car's performance while in extended range mode, the engine is never used and cannot be used to enhance performance while in electric mode.

 

[Saghost]

From MotorTrend:


My point remains... there is more than simply range added. The car's performance characteristics are different, some of which is due to the mechanical engagement of the ICE.

No. The degree of mechanical engagement of the ICE is identical in normal mode and mountain mode. That "Propulsion Power Reduced" message (they got the language wrong) shows up during steep ascents because the car has already run through the kilowatt hour or so of working buffer it keeps and is now reduced to running solely on the power of the gasoline engine, something that never happens in normal operation.

Mountain mode avoids that by having more than four times the available buffer, so that there's always enough energy in the battery to supplement the engine. (Of course, any buffer can be emptied if the load goes on long enough. However, GM sized the Mountain Mode buffer so it won't happen on any mountain in our road system.)
Walter

- - - Updated - - -

I have a a Volt and was consciously monitoring the battery/engine use screen for this on my drive home last night. It seems that only when the battery is depleted will the ICE drive the wheels directly as indicated by the power flow screen showing Battery and Engine use at the same time. The only other times the engine will come on are if you put it in Mountain mode or if it is extremely cold out and the cabin needs additional heating for a short time. Outside of these modes I have never experienced the ICE running when the battery has charge.

When its charged the Volt drives and feels just like an electric vehicle. I was doing 140km/hr no problem on battery. Try doing this in a traditional "Hybrid".

The screen lies.

Anytime you're driving above 36 mph and not accelerating hard while the engine is on, the car will be in power split mode, with the engine providing some drive torque mechanically.
Walter

 

[ItsNotAboutTheMoney]

To me it doesn't matter whether it's a serial or parallel hybrid or both (it's both). GM did what was most efficient, and that is entirely appropriate. Why would we want them to design a car that is less efficient than it could be?

The Volt is clearly a plug-in hybrid electric vehicle, or PHEV. That's great - it's a decent bridge technology to pure EV. Their marketing division can call it EREV if they like, but that's really just another word for PHEV with some arcane technical details to make the distinction. What matters to drivers is the full electric range, fuel economy, and performance - what the car does, not how the parts are connected internally or what their marketing people call it.

The EREV distinction is very much not about arcane technical details, it's about a very real differences in owner experience. The salient questions are:
(1) Will the car turn the engine on even if I'm driving within battery range?
(2) Will performance be limited in EV mode such that I'll want it to turn the engine on even though I don't need it to complete my journey?
(From a marketing perspective it was
(3) Is it like a Prius?)

For the Volt the answers are
(1) Mostly no. It needs the engine when (a)* it's 15F or below or (b) it runs the engine for maintenance reasons because you haven't needed the engine for a long time.
(2) No
((3) No)

* (1)(a) is my personal Volt bugbear that I hope they'll deal with in Volt 2. My wife's main peeve is that she likes to drive in Sport, but if you put the car in Hold it goes back to Normal pedal response. I hope they'll rethink the mode selection in Volt 2.

The i3 REX is also a PHEV, but really, if someone asked you to describe the i3 REX would you really, really start by calling it a plug-in hybrid? To me, that's just a more extreme case.

 

[scaesare]

Again, some of the modes provides capability that would otherwise be unavailable if the engine were strictly generating electricity:

Another example from Edmunds:

Mode 4: High-speed series-parallel hybrid mode up to top speed. This is classic gasoline-powered series-parallel operation. You can't have both electric motors driving the car at high speed like we saw in Mode 2 because the battery is discharged, meaning that the second motor-generator must continue to be a generator driven by the engine. This is where the engine begins to directly drive the ring gear. The engine is already clutched to the second motor-generator, so a straight-through mechanical connection is established when the ring's motor-generator clutch is engaged. Compared to Mode 3, the engine works harder here because it is simultaneously driving the ring gear and the shaft of the generator.

Again, my objection is not that this is a bad design. My objection is that EREV is a marketing term that attempts to suggest the ICE provides additional ELECTRIC range. What it actually does is proved additional range in many cases by mechanically providing torque to the driveline. However, so does a Prius, albeit via a different design.

Hence, Edmund's conclusion, which I agree with, is:

According to the conventions of automotive engineering, the Volt is a series-parallel plug-in hybrid, similar to the plug-in Prius.

 

[Duckjybe]

The screen lies.

Anytime you're driving above 36 mph and not accelerating hard while the engine is on, the car will be in power split mode, with the engine providing some drive torque mechanically.
Walter

Any proof?