Featured Plug-In Hybrids No Greener, Or Even Worse, Than ICE Models, Study Finds

I came across that opinion. It's based on ignorance of the terms. Perhaps they would understand the synonyms better; weak and strong. A strong(full) hybrid has a motor powerful enough to move the car on its own. If the motor is less powerful than that it's a weak(mild) hybrid. This leaves a wide range of what constitutes a mild hybrid. The minimal, weakest, is just start/stop with some regenerative braking; the motor doesn't help move the car at all.

The 48V system is on the weak end, though the motor can add some torque to give a little boost to the engine. That's how Ram is marketing it here; they don't even mention hybrid. In practice, the benefit to fuel economy is small, but the low means making it a standard feature is feasible. Which is what will happen in Europe with their emission laws. So little benefit individually spread over everybody.

This Subaru system is a mild hybrid. The more powerful battery, and slightly more powerful motor means it should assist the engine more. The question why did they use it when they had a full hybrid system that worked with their AWD system in the Crosstrek PHEV.

Sounds like your journos are a lot like ours. They are heavier on the go pedal than most people.

 

Really? We've known for years Toyota will be advancing plug-in hybrid tech & design. Looking closely, we can already see steps being taken to make that happen. Crystal balls can be found.

The most obvious comes from those who chose to complain & whine about how Prius Prime carried its battery without ever bothering to study the rest of the fleet. If they had, they would have discovered the C-HR platform is really Prius with a raised floor. Looking further, we see that the new Corolla Cross is basically just a Corolla with a different body... one that could also be raised. Ever look close at how RAV4 hybrid became RAV4 Prime? Toyota just raised the floor to squeeze in batteries. Turns out, the same treatment happened with Lexus XU300e. It doesn't take a crystal ball to see how Corolla Cross (or some variant sharing that platform) could become the next plug-in hybrid.

 

Defending the poor battery packaging of the Prius Prime, and claiming testing can be done on cars that don't exist just adds to the foolishness you are showing on this thread. I have shown what you have perceived as flaws and agenda in these studies isn't so, but since you have me on ignore, you will continue on in ignorance.

 

Price premium for a 48V mild hybrid should drop to less than $1000. In Europe that will be essentially $0 because of regulations and how the WLTP tests work. This will drive down component costs. At its simplest a 48V system only needs a 48V lithium battery and and a DC-DC converter to charge the 12V accessory battery from it. The Alternator and starter may even be less expensive in 48V spec. Over the next decade if it becomes standardized in Europe 48V components will replace todays 12V accessories, allowing thinner wires as only 1/4 of the amperage is needed to provide the same power. Electronic AC, Stering, active suspensions, safety systems all may be less expensive standardized. Of course, then the 12V battery and dc dc converter may go away.

That will kind of kill off the 0.5kwh-3kwh higher voltage non-plug-in hybrid. Yes this

The question is though will a RAV4 hybrid sell well if it is only $2000 less expensive than a more powerful Rav4 prime. As lithium batteries drop in price that is where we are going. The hybrid needs the extra safety equipment and the mg. As lithium batteries continue to drop in cost, my guess is the $3000 premium for a hybrid versus a $5000 premium for a more powerful phev is going to kill that middle of the road. A 48V system may easily get the same mileage on long trips as a hybrid, the difference is city, and a plug-in will get much better there. Right now toyota does not have the battery supply, but think 5 years out. A dedicated phev platform makes a lot more sense than hybrid, while the mild 48V hybrid is likely for europe for start stop regulations to use in existing designs.

 

That's an odd assertion. Where was the study that measures two identical vehicles, one using the Toyota Synergy design and one using only the 48V start/stop design? Mild hybrid systems typically only reduce pollution when at a stop or coasting. A full parallel hybrid like the Prius can and does reduce pollution throughout the driving cycle while maintaining drivability and efficiency.

One of the features that make the mild hybrid attractive is the lower cost of the limited battery pack. Unfortunately that same battery pack also limit's it's ability to regenerate electricity when stopping / coasting. The Plug in excels in recapturing energy that way.

Looking for cars available in MHEV and conventional mode is tricky. Many manufacturers don't make both options for the same mode. I did find a Land Rover ( 2020 Land Rover Evoque MHEV ) available as an MHEV and conventional. Both had with an EPA combined 23 MPG. Both had about 390 grams per mile CO2. You can compare cars at Compare Cars Side-by-Side

The Rav4 Prime, on the other hand, was rated at only 72 grams per mile CO2 and 38 MPG when even if it's never plugged in. 94 MPGe if you plug it in daily.

I don't see where an ICE with comparable comparable usability can even come close.

Dan

 

On the highway, nearly every hybrid is going to have the engine on 100% of the time. Hybrids that get better than a conventional cars on the highway do so by having an engine that trades power for efficiency. Not all hybrids do that, even full ones.

The Land Rover does get better city MPG with the mild hybrid system, and the EPA test cycles don't do a very good job of showing the benefit of a start/stop system. The highway did go down, likely from increased losses with the system in place. Both are using the same engine, which is a disadvantage for these early 48V systems; the drive train design isn't optimized to get the full benefits from system. Your Rav4 example is using a hybrid system with 2 decades of refinement behind it.

The Ram 1500 has a mild hybrid system. Standard on the V6 and optional on the V8. You won't see hybrid in any of the marketing, and Ram is advertising it as a torque booster.

No conventional car is going to best a PHEV in emissions and fuel efficiency. Unless, of course, the PHEV is never plugged in.

 

Let's start with the fact that by 2016, There were over 1.6 million Prius models on the road in the US. 51.5 percent of the hybrids sold in the US in 2014 were Toyota. Those are using a full parallel hybrid design. So the "Nearly every hybrid" part is doubtful.

Since this is Prius Chat, you should at least learn a bit about how the Synergy Drive works. To over simplify it, the ICE runs only as it's needed. When the optimum RPM creates more power than is needed to move the car the excess is captured by the MG and stored in the battery.

But here's the trick. When the battery reaches a pre determined SOC the ICE shuts off and the car runs off the electric motor. When the battery reaches a certain level of discharge the ICE fires up and the cycle starts over again. I have watched the transition and estimated that my 2002 Prius spent about 1/2 the freeway time with the engine running.

You end up with an engine that is either running at optimum speed in Atkinson cycle mode or it is totally shut off while the car travels at freeway speeds on the battery. So the part about "Hybrids that get better than a conventional cars on the highway do so by having an engine that trades power for efficiency" is also invalid.

The primary value of a mild hybrid is that it is cheap for what it delivers. A 5 MPG increase is really good for a truck that gets 25 MPG.

Dan

 

Always good advice, good enough that it's worth considering whether it could be addressed to you.

A typo, or did you mean a 2002 Prius, the first generation, the sedan? What are the typical freeway speeds in your area? Have you looked up the maximum road speed at which a Gen 1's engine can be shut off?

 

Yes, I owned a 2002 Prius. As I recall, it would run up to 43 MPH with the engine stopped. Over that the MG would spin the engine, using the drag to direct the power from MG1 and MG2 to the wheels. That's what I recall. It's been a Loooooong time since I researched it.

Just for yucks.... The typical freeway speeds here can average from 20 miles of stop and go (32 miles in 1.5 hours) during rush to 85 MPH late at night.

 

Yes, over 43 the engine is invariably spinning. If it is spinning and fuel injected, it is providing energy. If it is spinning and not injected, it is using up energy, which is useful for decelerating when the battery is too charged to accept more, but would be wasteful under any other circumstance. The HV ECU does a pretty good job avoiding wasteful behaviors.

 

There's no excuse. Participating here for 15 years, yet having no idea how Toyota's hybrid system (by far, the most abundant) actually works...

Take an engine, any type of engine, connect a power-split-device with 2 motors. Use the smaller motor to collect waste energy, since an excess is available while cruising on the highway compared to city driving. Convert that energy from mechnical power to electricity stored in a battery. Later, use that electricity to supplement energy from the engine by throttling way down or stopping combustion entirely.

In short, no tradeoff necessary. True, one that does will result in even better efficiency. But that isn't required... but you should have already known that. Who's ignorant?

 

Very nice write-up. I typed my reply, quite annoyed by his constant badgering, then walked away without posting to enjoy a nice evening with my wife. Coming back afterward to find your thoughtful remarks added to sense we all need to be constructive. That was much appreciated. Thanks!

On a topic like this, we all need to be aware of the bigger picture. There are forces from every direction attempting to undermine progress, especially when it tips heavily in favor of a legacy automaker who really studied the situation and worked hard to ignore the rhetoric. I try to do the same. But if misinformation is posted, it needs to be called out at some point.

 

I could, of course be wrong. I last looked into the drive almost 20 years ago, and a lot has happened since.

Assuming your assertion is right that the ICE is provided fuel whenever the car travels over 42 MPH, what mechanism allows you to use virtually no gas when you are scooting along at 60 MPH on the 60 mile downgrade (US 50) from Lake Tahoe (7500 feet summit) to the flatlands outside Sacramento? Given that the ICE runs at a minimum of 1000 RPM and the max ICE speed is around 4000 RPM, it should be using a significant amount of gas on that downslope.

Dan

 

Large scale adoption of 48V systems will be happening in Europe first. Toyota has the top selling hybrids there, but the Prius isn't one of them; it isn't even in the top ten. Toyota itself is number 9 in sales of the makes there, behind Ford. Without the hybrids, they'd have less market share.

Many of the hybrids and PHEVs available from others there are power hybrids that don't prioritize efficiency to the extent that Toyota does.

Had a 2005. At speeds over 55mph, I only saw it go into electric mode with feathering the accelerator. Otherwise, it had the engine running most of the time at those speeds.

HSD isn't a parallel hybrid. It is a power-split that is capable of both parallel and series operation. Hyundai uses a parallel system, and is capable of high efficiency, while possibly being lower cost. Or it can be like the system in the Explorer, whose design chooses to retain the full performance of the ICE model, and gets 28mpg to 26mpg on the highway while combined is 27 to 21.

Atkinsonation is exactly trading power for efficiency. Toyota has Atkinson and Otto cycle engines build on the same block and of the same displacement. The Otto cycle ones produce more power while burning more fuel. Now, valve timing is reaching the point where an engine can come close to running in Atkinson or Otto as needed, but it is an expense not needed in a full hybrid.

The entire reason the Prius and similar hybrids can attain the fuel efficiency they have is because an engine that can efficiently supply the power the car needs the majority time. The electric side of the system covers for such an engine's weakness in the car, since the engine alone would mean acceleration that is unbearable for most buyers. Engine shut off and regen braking are add on benefits.

Which is why 48V systems will come to replace ICE cars in Europe. Full hybrids do better, but the extra cost can be too high for some segments. In Europe, it's hybrid premium plus VAT.

Familiar with how it works, and the idea behind it. For a given car, an engine is chosen that can efficiently supply power for the times the car spends the most at; cruising at steady speeds. Such an engine is under powered when it comes to acceleration and climbing though. The electric motor and battery provide the extra power needed at those times. They provide further efficiency enhancement through regenerative braking, allowing the engine to run at peak efficiency speeds more often, and safe engine shut off, even while the car is moving.

In a power split, or series/parallel system, a fraction of the engine's torque is always going to the smaller motor/generator, which works as a generator at this point. the electricity can go directly to the traction motor(series mode), or to charge the battery. The system also varies the smaller motor operation to simulate a CVT, thus why eCVT is used to describe their transmissions. Parallel mode happens when electricity from the battery is used by the traction motor.

Now, what about the thread's original topic?

 

I have not had a Prius in my hands since March 26, 2019. But I remember:

• 2001-03 (Gen 1) - had a speed limit on one of the motors that required the ICE to turn to avoid over-speeding. However, this did NOT require burning the rate of fuel for a significant amount of power.
• 2010, 2017 Prius and Prime - the internal gearing significantly allowed faster rotation that mean the engine could be turned off at higher speeds.
• operating line at peak efficiency - the Prius control laws keep the engine either OFF or in a PEAK efficiency range. The traction battery can 'bank' excess energy from a higher than needed power cycle and then turn the engine off and sustain the car using the stored excess energy.

I appreciated the efficiency of our Prius until a practical EV, the Std Rng Plus Model 3, came along. For me, switching was trivial and we have 32,260 miles at ~$0.025/mile which is significantly less cost per mile of the Prius Prime.

Bob Wilson

 

Look at my other post. It's pretty much a given that Conventional ICE designs would have a hard time matching the emissions of a well designed PHEV even if it's never plugged in. A mild hybrid is not a "well designed" PHEV.

If you think you have instances to the contrary, try running it through the comparisons at Compare Cars Side-by-Side. That's a tool that is about as impartial as you could hope for.

You must, of course, make sure that you are using similar cars with similar capabilities and you must use the same measurements for both.

Go for it. Knock yourself out.

Dan

 

Car and driver tested long highway trips camry versus camry hybrid. The hybrid was 5% better, not much. A 48V mild hybrid will have a lower drag on the engine, so would likely be even less of a difference. Engine efficiency difference is less than 2% at highway speeds. So not much there. The tests aren't really long distance tests, but lots of hybrids sold here, and they don't really outperform by much, definitely not like the epa test would tell you. Hyundai's 48V hybrid battery is 440 wh, bosch's 300 wh toyota in the prius uses a lithium 750wh battery as a option. Not that much difference, but the safety for higher voltage and the costs of the motors has made it hard for them to bring down the hybrid premium. Remember the 48V system is fairly new, an first put in cars that need bigger than a a standard 12V lead acid battery (not prius type cars). An active safety and electric AC get more prevalent, there will be more and more.

The difference is going to be as I said will be in city driving and YMMV! And as I said if you really are doing a bunch of 20 mile drives in the city a phev is going to be much more efficient than a full hybrid. You don't really design it the same way as a full hybrid with a small battery. You use less expensive lower power density batteries. You don't need as big of a mg1 as you can use the battery at low speeds, and for similar acceleration engine can be downsized or better acceleration can be achieved. If you are paying that hybrid premium, why not do it right?

 

Will do. Compare Side-by-Side


Those are two of the cars tested by Transport&Environment. The third, the Outlander PHEV, is the big seller in Europe, but the US hasn't gotten the newer model with efficient Atkinson engine engine yet. The Volvo is the number two PHEV there, but is quickly followed by the Passat, its sedan and wagon siblings, and BMW 330e. The BMW X5 PHEV is new at number nine, but 36.6% are choosing the PHEV over the conventional model. The Kuga(Escape) is close with 35.5%, but the only one better is the Outlander with 81.1%.
European sales 2020 first half EV and PHEV - carsalesbase.com

Fueleconomy.gov only posts the combined MPG for PHEVs, so we will compare those. The Volvo hybrid does better than the conventional, but just 12.5% better. This is far from the 33% improvement the Rav4 sees with HSD, and the over 50% of the Camry LE. The X5 hybrid's combine rating is actually worse by 13%. Perhaps that reduction is related to the emission controls, but a manufacturer can choose to apply a lower rating to a car. Past Prius had a worse rating outside CARB states, despite being the same engine.

The site includes a CO2 emission value for PHEVs based off an assumption of EV and hybrid driving. They don't disclose what that assumption is, nor allow a personalized ratio to EV and hybrid, but CO2 emitted directly relates to fuel burned. The Volvo will emit less at 328g/mi, and BMW more with 440g/mi.

For completeness, here is the Outlander. The PHEV is rated 1mpg worse, but with the rounding used on the figures, it could be the same. The updated Outlander PHEV will have better fuel economy and EV range, but the conventional model might have its own improvements.
Compare Side-by-Side

 

Hmmm. How is this different than the mild hybrid available for the last 20+ years? Or is it a technology that is just now being adopted to satisfy a European ecological mandate of some sort?

 

Past mild hybrids all had a larger battery of the voltage that required the additional safety measures. They also may have had a more powerful motor. 48V is under the 'stop your heart immediately' threshold if you touch a bare wire. There was talk of moving cars to a 48V electrical system back when hybrids were still a new idea, because of increasing loads from accessories. The accessories themselves got more efficient, so the move wasn't needed.

The current 48V systems have an arrangement a lot like GM's BAS/eAssist and the front end of Hyundai's system. There is a small motor/generator, Hyundai calls it an HSG(hybrid starter generator), that bolts onto the engine, and connects to the drive train through a belt; Hyundai's HSG is 10kW. It replaces the starter and alternator. With the smaller battery, it is enough to add some torque to the engine, but can't do anything without the ICE. For those that use the assist term for hybrid systems, it would be on the weak end.

The cost and design means it is easy to add to an existing ICE car. The issue with that is that the improvement won't be the best. Have to design the drive train with the mild hybrid in mind. Future generations will move the HSG to between the engine and transmission, or after the transmission, where it can add more assist to propulsion.

It is tightening emission standards that is driving its adoption in Europe. It is also the bare minimum that China will require on an ICE car soon. If CAFE targets get readjusted, there is a good argument for them to arrive in the US; many new models already have start/stop systems.