A few weeks back, we took a look at a Chevy Bolt with a silly contraption hanging off the back. We dived into the science, and looked at why hooking up a generator to the rear wheels wouldn’t let the EV recharge itself and drive forever. That topic raised an interesting question—don’t hybrids do the same thing? Why do they work?
From the outset, it’s worth noting that yes—hybrids do turn wheel rotation into electrical energy! Now, hybrids can’t drive forever without recharging or refueling, but they are often more fuel efficient than cars that just rely on internal combustion engines.
This can be confusing. You could be forgiven for thinking that all the extra weight of motors and batteries would have a negative impact, not a positive one. You might also think that converting the chemical energy of gas into electricity would waste energy. And yet, through nifty engineering, hybrids do come out ahead. Let’s explore why!
Play To Your Strengths
Let’s start by examining a series-parallel hybrid like the Toyota Prius. It can drive the wheels using its engine or the electric motor, or both in combination. It can also charge the battery using the gasoline engine, or by using regenerative braking. Let’s ignore regenerative braking for now, and examine the Prius on this basis.
For a regular car, the chemical energy in the gasoline is turned into kinetic energy, with some losses in the process. But the Prius is more complicated. Setting aside regenerative braking, all the energy used by the car still comes from gasoline. [Ed note: I added the blink effect below to highlight the power flow discussed in each caption. – Pete]
The engine burns gas, turning it into kinetic energy to drive the wheels. The Prius also converts kinetic energy from the engine into electricity to charge the battery. The electric motor can then draw from the battery, turning that electrical energy back into kinetic energy to drive the car. Even then, it’s worth remembering—the electrical energy in the battery originally came from the gas burned by the engine.
Those extra conversion steps come with losses when the Prius turns gas into electricity. The generator in the Prius can’t turn 100% of the engine’s output into electricity. Some is lost as friction or heat. Similarly, the electric motor isn’t perfectly efficient either. It has friction losses, resistive losses, and others besides.
Converting gas into electricity and back into kinetic energy involves multiple extra steps. The losses involved are measurable. And yet, a Prius comes out as more efficient than many regular gas cars. Even when it’s carrying around the extra weight of a motor and battery! How is it even possible?
It all comes down to the quirks of the internal combustion engine. They’re most efficient in a very narrow operational range. Outside that range, they’re often not making great use of the energy in the fuel.
Hybrids get around that with a nifty trick. In those situations where the gas engine isn’t very efficient, like low-speed operation, the engine can be used as a generator instead, charging the battery. When being used to generate electricity, the gas engine can be run in its most efficient power band to get the maximum energy out of the fuel. The energy it generates can then be stored in the battery and used to run the electric motor.
This works because the electric motor is far more efficient than the gas engine in many situations, like low-speed city driving. Even though there are more energy conversions involved, the combination of engine, battery, and motor comes out ahead. This is because the engine is being run in its optimal power band to get the most out of the fuel. This strategy is more efficient than just using the gas engine in low-speed contexts where it can’t run at its most efficient speed.
As an aside, this is why automakers keep putting more gears in gearboxes. A 10-speed gearbox will allow the engine to run closer to the RPM for peak efficiency across a far greater range of road speeds. Compare that to a car with an old two-speed auto, which will be outside the engine’s most efficient RPM range at most speeds.
Diesel-electric trains take advantage of the same concept. A diesel engine isn’t very efficient when it has to run at varying speeds all the time. Instead, diesel-electric trains run their combustion engines at near-constant RPM where they are most efficient. The engines are hooked up to generators which drive electric motors at whatever speed is required to run the train. Electric motors happily run at different speeds with much less loss of efficiency than internal combustion engines. Even though there is a loss involved in converting the diesel engine’s kinetic energy into electricity, it’s more than made up for by the improved efficiency of the electric motor in different speed ranges.
Love Me Some Regen
Okay, so we ignored regenerative braking to start with. Now let’s dive in. It’s another great tool that hybrids have that helps them save fuel compared to regular ICE cars.
When you accelerate in a gas-powered car, you turn fuel into the kinetic energy of the vehicle. The faster you go, the more kinetic energy the car has. If you then allow the car to coast down, that kinetic energy will slowly bleed off through air resistance, rolling resistance, and other minor losses. But we don’t drive like that. Instead, we inevitably end up hitting the brakes. We just burnt all this gas just to get this kinetic energy, then we apply the brakes and turn it into heat. It’s gone.
Hybrids, on the other hand, can capture this energy. Instead of using friction brakes alone, they can connect their drive motors to the wheels, using them as a generator instead. In this mode, the generator turns the kinetic energy of the vehicle into electrical energy to be stored in the battery. The resistance of the generator slows the car down significantly, much as the friction brakes would have. But instead of losing the energy as heat, it’s put back into the battery where it can be reused to drive the motor.
Of course, the energy you get out of regenerative braking is less than you put in. However much energy you got out of the battery or gasoline accelerating up to speed, you’ll get less back when you regeneratively brake back the vehicle. But you’ll get some, and that’s more than the zero that ICE cars are getting.
For this reason, stop-start city driving is perhaps the best example of a hybrid’s strengths. An internal combustion engine will burn lots of fuel accelerating the car from slow speed, and lots is wasted every time the car has to brake or stop. Meanwhile, a hybrid can often leave the combustion engine switched off in these scenarios. Instead, it will rely on its electric motor, which is more efficient than a combustion engine at low speeds. If it has to stop, it can use regenerative braking to recapture some of the energy it just used accelerating.
This is why hybrid cars are so good in city traffic, but less so on the open road. In highway scenarios, braking events are rare, so there’s little energy for the hybrid system to recover. Plus, in these situations, the internal combustion engine can usually run close to its peak efficiency. There’s also the need to overcome greater air resistance at high speed, where the high power output of a combustion engine comes in handy. Indeed, this is why hybrids will use their gas engines more heavily on the highway.An an aside, this is also why EVs also tend to get lower range on the highway. Their electric motors are pretty efficient everywhere, but they lose the benefits of regenerative braking when they’re driving at continuous speed.
Benefits On The Side
Hybrids come with one more main benefit compared to their ICE cousins. They can usually use smaller, more efficient engines than comparable gas-only models. The engine can be smaller because it doesn’t need to generate peak power alone; it can combine with the electric motor to hit the necessary figure. Plus, the engine doesn’t need to be tuned to deliver as much low-down torque. Instead, the electric motor can serve well in this capacity, as they generate peak torque right from zero RPM. This is also a huge boon for low-speed drivability.
It’s also worth noting that hybrids have traditionally been designed for peak efficiency across the board, in a way which regular models are not. Hybrid models often get sleeker, more aerodynamic designs, lower-rolling resistance tires, and other features to further improve their efficiency figures. These design choices have, at times, come with tradeoffs like lower cargo space or a less attractive body. But for a model that specializes in efficiency and good fuel mileage, it’s considered worthwhile.
Sum It Up
Ultimately, hybrids come in all different kinds. You get parallel hybrids, where the engine and motor work together to drive the wheels mechanically. Meanwhile, series hybrids use internal combustion engines solely as generators. The engine in these vehicles cannot mechanically drive the wheels. Then you have the more complicated series-parallel hybrids, where the engine and electric motor can work together or independently as required. The popular Toyota Prius falls into this latter category, which is perhaps the most flexible.
Then you have plug-in hybrids. Everything we’ve said about hybrids still applies to them. However, they can be even more efficient, because you can charge them with electricity from the grid. Rather than turn gasoline into electricity with your engine, you can use solar panels or your local neighborhood powerplant to fill up the battery instead. That powerplant is most assuredly more efficient than your combustion engine at making electricity.
[Ed Note: I’d like to add a note about downsizing opportunities and city-traffic-idling. Actually, I’m just going to quote the Department of Energy:
In an HEV, the extra power provided by the electric motor may allow for a smaller combustion engine. The battery can also power auxiliary loads and reduce engine idling when the vehicle is stopped. Together, these features result in better fuel economy without sacrificing performance.
I also want to note that with improved powertrain efficiency afforded by hybrid technology comes a reduction in overall system heat rejection, which means lower cooling requirements, which theoretically means a smaller required frontal cooling (grille) opening and thus improved aerodynamics.
Oh, and wow that’s a nice car above. -DT]
Whichever sort of hybrid you have, the basic concept is the same. The combustion engine is allowed to operate in its peak efficiency range more often, thanks to the electric motor helping out with drive duties. That’s how they’re more efficient than regular ICE cars. Furthermore, they are also able to recapture energy under braking, and they enable vehicles to get by with smaller, more efficient engines.
Hybrids have become a huge part of the automotive landscape. While EVs continue to improve, don’t expect the hybrid model to die out anytime soon. If anything, it could keep the internal combustion engine alive longer than you might imagine!
Image credits: David Tracy, Toyota, Honda, EPA, Ford, Laurent Jollet via Unsplash license
Tks for the article. I can understand why it was written bc hybrids and PHEVs are more common now, they are still in the minority and I would expect likewise the number of people that understand how they work is also in the minority.
I have a 2012 prius phev which I liked enough that I bought its successor, a 2017 prius prime (also phev), both serve as daily drivers for us. I’ve been impressed with how much more advanced & refined the Prime is over its predecessor. Although it is supposed to have only a max of 25 miles of all electric range, this morning ours was showing 32.4 miles all.electric range.
On the current tank I have just shy of 800 miles and the gas tank is still 3/4ths full. If this rate continues through the year, I expect even if we drive it 12.5k miles (outside of a long vacation road trip), we’ll end up only filling the gas tank 3-4 times per year from commuting which is exceptional.
Pilots talk alot about picking a plane based on the average missions they expect to be their average / most common use case. I know we’re enthusiasts here so dd choices aren’t made by rational considerations alone, still I think there is a lot of wisdom, (certainly financially), in treating one’s daily driver choice similarily.
I’m not shitting on the article, I’m shitting on the need for the article.
People really don’t understand why a hybrid gets better fuel mileage? Yikes.
So this is a good primer on hybrids. How about followup deep dives on ways ICE can be made even more fuel efficient and cleaner?
Things like:
Hit and miss
5+ stroke cycles
Cylinder deactivation
Water injection
Compression ignition
Pilot ignition diesel
variable displacement
Ceramic engines
Non piston engines
????
Use the theoretical efficiency limit of ICE as a goal and give us some idea of the potential efficiency gains, the advantages (other than efficiency) and potential drawbacks of each tech.
Inquiring minds want to know.
Reducing weight would help.
Has anybody figured out how to use the power of gravity to create more energy? I mean you are traveling at 55 mpg then you start going down a steep grade which will speed a car up past the speed limit. Sure keep hitting the brakes and you get some regenerated energy but wouldn’t the steady slowing down of cruise control work better?
“Has anybody figured out how to use the power of gravity to create more energy?”
Yes. Its called a hydroelectric dam.
Also solar fusion but that’s a harder nut to crack.
Essentially this has already been done, First, you don’t have to hit he brakes to maintain speed downhill you just let off the gas a little, or all the way and coast. If the hill is steep enough for long enough The toyota hybrids have a “b” mode for going down mountain passes that is programmed to use the regenerative braking heavily so you miantain speed without touching the brakes.
The “b” mode on Toyota hybrids also works very nicely in low traction scenarios.
In addition to heavily using regen. it also is like downshifting on a manual transmission car where you get the advantage of engine braking to slow down the vehicle as well
A hybrid vehicle consumes different kinds of “fuels”; more than one “fuel” source. A plug-in hybrid is a true hybrid, the regular Prius was never a true hybrid but use a battery-electric boosted drivetrain and a single fuel: gasoline. People talk about the drivetrain being hybrid, but overall the car is single-fuel.
This is pedantic until you start to question and answer why the Prius saves fuel.
Depends on definition of fuel? Anything that generates energy is fuel right? Solar panels?
The propulsion comes from two sources combustion and electric that is the hybrid they are referring to. I think it’s a good catchy name that let your average consumer know what to expect out of the vehicle. GM had a very hard time selling the Volt/Ampera because many consumers thought that it was only an electric vehicle and with its 40ish miles of EV range many consumers never looked further into it.
to me, the hybrid nomenclature is related to the propulsion not the fuel to drive the propelling devices. By your definition, is an e85 compatible vehicle a hybrid?
A side benefit of some hybrids is the ability to provide auxillary power when needed to external users. We have used our Prius and Rav4 hybrids to generate power for our house when PG&E shuts down for whatever reason. A quality inverter provides power throughout the house via extension cords. Uses about a gallon a day. A Sprinter-scale hybrid van is the ideal boondocking RV, where is it? Yeah, outside the US probably.
This is a great and timely post.
Our family swapped our older ICE vehicles for new technology.
Unfortunately for her, it was due to her then-new vehicle being destroyed in an accident. Fortunately, she is doing well afterwards as is my son (it was a best-case scenario of a worst-case incident, if that makes sense).
She picked up a Genesis GV60 as a replacement (all-electric). I drive a Kia Sportage Hybrid (SX Prestige, not the pHEV version). It is remarkable how both vehicles have changed our driving habits and frankly, are worlds ahead of the ICE-only vehicles we owned.
The Sportage is a series/parallel hybrid and is an absolute joy to drive. No worries about performance, mileage is so much better than the vehicle it replaced (2018 Kia Sorento SX V6), and it fits in the garage. I gave up a little bit of interior room that frankly I don’t even notice. No missing creature comforts in either vehicle.
There is something just almost magical being able to “start” either vehicle, set it in Drive, and nearly silently pulling away (except for the Virtual Engine Sound System or VESS letting pedestrians know we’re rolling through).
My partner hates going to the gas station, and now she doesn’t have to thanks to a Level II charger installed essentially for free. Duke Energy provides a rebate that covers installation cost.
We’re never going back to gas-only vehicles.
I loved my Toyota Camry Hybrid. 42 MPG doing my normal NY driving style and not trying to play the MPG game, and over 45 when I was. If it weren’t for the space limitations, I’d still be driving it. Alas, trips with 3 people and a person sized dog do not make for comfortable 4 hour sessions…or the weekend yard sale excursions…I truly wish that there were more large hybrids for AFFORDABLE prices…alas, not meant to be, at least until the newest batch hits the used car lots….
Toyota Highlander hybrid has been available simce I think 2006 amd has a 3 rows even if the 3rd row is not the biggest in the world that might work for you.
Or
there is the Sienna hybrid if you’re OK driving a minivan.
Sadly I don’t think either has been offered as a phev though.
In fact off the top of my head, sadly in the US market, I can’t think of any phev 3rd row vehicles and I’m not counting the Chrysler minivan bc of how poor their reliability has been
I bet next car hybrid or ICE. New stories all the time about people switching back.
My father purchased a 2020 Ford Fusion Titanium Plug-in Hybrid several years ago, the last model year that was available from Ford. The car only gets 30 miles on its battery but despite him driving about an hour / 55 miles to work a few days a week, he’s currently averaging 70mpg. He told me he would not have believed it if not for the fact that he simply doesn’t put gas into the car nearly as often as he used to with his last car (which was a non-hybrid Fusion) making the same typical weekly drives. Just about all the local drives he and my mom make are pure electric.
So maybe just maybe autopian should write an article actually explaining when weight does and doesn’t matter for a car’s efficiency. Because most of the time, it actually doesn’t really.
Size matters a LOT, and having an engine/propulsion system properly sized so that it can operate in an efficient regime as much as possible matters a lot (this is why smart cars get such terrible gas milage, too small engine runs inefficiently). But weight often doesn’t.
Adding 10% of a cars mass for batteries or motors (and it really doesn’t need to be that much), might add <1% total frictional losses at HWY speeds. At city speeds, duty cycles are so biased towards energy recovery/kinetic shedding, that the delta in RR is completely negligible compared to the energy expended to go up and down in speed.
Plus we have talked about this before in the comments, but the simple physics of suspension means that I’d be willing to bet most cars, most of the time, are more efficient when more heavily loaded, since it compresses suspension more, and thus improves aero efficiency.
I don’t know it would be worth an entire article. Weight is bad when you are accelerating or gaining altitude. It is good when you are decelerating or loosing altitude with a Hybrid/PHEV/EV. It is essentially neutral when cruising at a steady state speed on flat ground.
Bookmarked as a “reference post” – thanks Lewin!
I daily a Prius 3 and can’t think of a better car for this. It’s always funny, how most of my car nut friends react, when I mention this. Even more when I say, that this choice is far from any accident, but very deliberately 🙂 It works fantastic, it can be quick and the mileage is absolutely fantastic.
I’m a car nut and I’d love a new Prius.
My dumb friend wants to know how an electric motor and an ICE can power wheels simultaneously.
Modern electric motors have very precise control systems, which allows you to run the motor at the exact same RPM as the gas engine. Once you’ve got them spinning at the same RPM, it’s a simple matter of connecting them to the same shaft using some combination of gears, chains, and clutches.
Sort of. Technically you don’t need to do anything fancy to make them cooperate at propulsion; at the end of the day it’s just more torque going to the wheels. Now, if you want to smoothly transition between ICE/EV/hybrid then you need control of the speed/power of the electric motor.
Nope, in two motor hybrids the motors and engine are all permanently connected together by the power-split device. It is just a matter of operating the motor/gen in motor mode when desired, generator mode in other conditions or just leaving it open circuit when neither positive (assisting) or negative (charging) torque is desired.
Imagine a rear differential, with the engine attached to one axle shaft and the electric motor attached to the other. Rotating one or both axle shafts will cause the driveshaft to spin, and the speed of the driveshaft will be the sum of the two speeds.
This is how the eCVT in the Toyota Synergy Drive works, and a number of other hybrids use a similar system. They use a planetary differential rather than spider gears, but it’s the same concept.
You’ve got the basics right but are missing a couple of details. The power split style hybrids use two motors. Think of that differential where the engine still supplies power to the driveshaft. On one side of the differential you have the starter/generator and the other side has the traction motor/generator and that output is what connects to the wheels.
For the engine to provide power to the wheels the starter generator must be operating in generator mode to force the mechanical power to the wheels. If the starter/generator is left open circuit it will spin and no power will go to the wheels. It is just like if you were to take a vehicle with an open diff and put one wheel on ice, rollers or lift it off the ground. Depending on the situation the power generated by the starter generator will be directed to the traction motor/gen, the battery or both. The traction motor may receive power from the starter motor/gen, the battery or both again depending on the exact operating conditions.
Send him this video: https://youtu.be/jofycaXByTc?si=SNFszTIHjGcn8SDU
That is one of the best videos I have seen, that gets it mostly right, thanks for posting it.
No problem. I spent a quite a while trying to wrap my head around how the system works. One day I spent some time going down the rabbit hole of how the previous Prius eCVT worked and stumbled on that video. It seems to get the concepts across a bit better than the video of the actual parts that led me down the path.
To see how the actual parts work inside the eCVT you could share this one: https://youtu.be/ZmHpSyTsfm0?si=oWV3qsSsliL0l_kn
It’s from an older model, but I’m betting the concepts are still the same.
Both of those videos seem to be illustrating the 2nd generation Toyota system. I am familiar with what I think is the 3rd generation system, as seen in the 2019-2023 Subaru Crosstrek hybrid. One difference is that the newer system has TWO planetary gearsets: the Power Split gearset connected to the engine & MG1 as seen in the videos, plus another planetary gearset connected to the output of MG2. This additional planetary gearset provides a torque increase/speed reduction for the output of MG2. This is a good thing because 3-phase AC electric motors will happily turn far higher RPMs than the gas engine will.
To sum up, MG1 has several roles in this system:
Meanwhile, MG2 does the following:
Now that you mention it, I think I’ve seen a breakdown of the one you’re talking about on the WeberAuto YT channel.
TBH, I was mainly concerned with conveying how they couple and decouple the parts smoothly (which was what I had a hard time picturing). The system is pretty amazing, and I love how they virtually eliminated wear parts so it should be extremely robust (assuming proper oil changes).
How can your left foot and right foot power a bike simultaneously?
The same way two people can use a two person saw; in cooperation with each other.
Mention should be made of the wonderful eCVT transmissions that only work in hybrids.Terrible name, since they have nothing to do with other CVT transmissions.
They are more like a differential. I suppose you could make one work with a ICE and some sort of mechanical integrator but that would at least double the complexity.
Yeah, the term “eCVT”, while technically correct (the best kind of correct), it really does a disservice to how brilliant the design is and is has absolutely nothing in common with the belt-driven CVTs everyone hates.
In reality, an eCVT is basically a mechanical adding machine letting you feed multiple power sources to a since output seamlessly through differentials and gears. It’s somewhat similar to a proportional tank drive that lets you vary power to each track without having to skid one. There’s no rubber-banding, no clutch packs, and it’s very compact.
CVT just means continuously variable transmission of which they both are. There are different types of CVTs.
Good job on explaining the often overlooked way that hybrids are more efficient, by operating the ICE at a higher efficiency point and using the starter/generator to harvest the excess torque, convert it to and store it as electricity. Then as needed using that energy to either operate w/o ICE assistance or lower the load on the engine again to keep it operating in that most efficient range.
However you left out the primary reason that a Hybrid can get better fuel economy than a standard ICE which is the use of an Atkinson like cycle rather than the old Otto cycle. Tracy touched on it slightly alluding the to better thermal efficiency of hybrids which is due to that Atkinson cycle.
The extremely late intake valve closing of the Atkinson like cycle reduces pumping losses, while making the engine operate at a much smaller effective displacement than the bore x stroke implies. However it retains the expansion stroke of the larger engine, capturing more energy and letting less out of the tailpipe. That is also why the listed static CR is so high because they operate at low VE.
Another big contributor is the engine off operation. Sure a lot of cars have stop start now, reducing idling losses, but hybrids allow the engine to stop while the vehicle is still in motion some as high as 80mph. So while going down that grade the engine can be stopped and the potential energy due to Mgh converted to and stored as electricity.
The electric A/C compressor on most modern hybrids also plays a small part. Being electrically driven means it can always operate at the most efficient point for the actual demand and thus be smaller than is needed when tied to engine rpm. Of course it also means that it can operate with the engine off whether in motion or while stopped.
I don’t think the “Atkinson cycle” is actually unique to the hybrids, nor universal to hybrids. This information is hard to find, and I’m not sure, but I am under the impression that Toyota uses this Atkinson mode on almost all of their engines now.
This needs to be clarified by someone who knows this for certain. I won’t pretend that I know for sure, but I am 99% sure that Atkinson cycle engines have only ever been used in a production vehicle when paired with an electric drivetrain. If someone can prove me wrong I will gladly admit my error, but I don’t think any gas-only Toyotas use atkinson-cycle engines.
Mazda used the Atkinson cycle in the Mazda3 2-liter Skyactiv-G in 2012.
Ok good to know. Do they still use it, or has it been discontinued?
All the Skyactiv engines are Atkinson cycle, including the current Miata.
No the Skyactiv-G and certain Toyota engines are Atkinson-Otto Cycle engines that can operate in both cycles and only operate in the Atkinson cycle in certain operating conditions.
That I can remember Mazda 1st used what one could consider a supercharged version of the Atikson cycle, the “Miller” cycle engine years ago in the Mazda Mellenia
https://www.carthrottle.com/news/mazda-once-made-225-litre-v6-and-its-weird-youd-imagine
Newer Camrys employ Atkinson on gas-only V6s, from: https://pressroom.toyota.com/2024-toyota-camry-style-and-performance-in-americas-best-selling-midsize-sedan/
The 2024 Toyota Camry is one of the few midsize sedans to still offer a V-6 engine, and this one is a gem. The 24-valve, DOHC 3.5-liter engine is equipped with the D-4S direct injection system, along with a specially developed VVT-iW (Variable Valve Timing-intelligent Wide) variable valve timing system for the intake, with VVT-i on the exhaust. The VVT-iW system can switch the engine to the Atkinson cycle, which reduces pumping losses by delayed closing of the intake valves.
My dad’s ‘23 4cyl returns 41mpg pretty regularly if you keep your foot out of it. It doesn’t call out Atkinson for the 4cyl but it’s both efficient and quick.
Theoretically a lot of variable cam phase engines can run in Atkinson (technically specifically Atkinson-Miller) cycle especially at idle because it produces lower torque. Hybrids can generally operate in it most of the time because having a torquey electric drive motor can make up for the lack of it from the ICE.
Well you add supercharging or turbocharging to Atkinson and it’s Miller.
Then there’s WW1 aircraft engines that used overcompression where they had high compression ratios but didn’t open the throttle completely at low altitudes.
I’m trying to remember an engine technology that varies between Otto and Atkinson or Miller by varying the intake valve opening times and lift and eliminates the throttle. It’s a lot easier without using camshafts as actuators. Camcon, Freevalve, and some Chinese company I forget the name of are working on this. It was the next big thing in Formula One before the FIA outlawed it for some stupid reason.
You are correct that the Atkinson cycle is not exclusive to hybrids and that there are some hybrids that don’t use it. However those non-hybrids are not Atkinson Cycle engines they are Atkinson-Otto Cycle engines where they only use the Atkinson cycle in certain conditions and the Otto Cycle the rest of the time. Meanwhile those hybrids with the big efficiency gains operate only in the Atkinson Cycle.
I don’t know about more recent Toyota hybrids, but I am certain that at least the older Prius engines do not run in “Atkinson” all the time, they can turn it off with the VVT whenever more power is needed.
That is not what the former Toyota factory trainer taught me back when the Prius was just a couple of years old. Yes they do vary how late the intake valve closes but never really cross the line into Otto cycle territory.
Now that I have a little more time it is the shape of the intake cam lobe that makes a true Atkinson cycle engine. It has more duration. The key is late closing of the intake valve, but still opening it at the usual time. With a cam profile for an Otto Cycle engine sure you can retard its timing to get that late closing, but you also end up with late opening which doesn’t reduce the pumping losses like a proper Atkinson Cycle does.
I wasn’t thrilled about purchasing a hybrid, but my wife was adamant when we replaced her car. I am now a convert. It is simply remarkable. Her ES300h is huge, quiet, comfortable, full of bells and whistles and is a lovely place to spend time. It regularly gets mid 40’s mpg in mixed driving, and my wife has a lead foot. That a car this size can get Prius level efficiency is simply astounding.
Since our first Hybrid over 10 years ago all of our daily drivers have been hybrids or PHEVs.
When the time came this year to replace my wife’s 2005 Acura MDX with a 2019 we were both thrilled to find her a hybrid. A huge amount of her driving is city stop-start and the hybrid definitely helps the situation. The 2005 was a nice car, but what a fuel hog – it was worse than my Suburban. The 2019 does a lot better.
Well written. I think longform content like this would also greatly benefit from a video format presentation, for people that like to multitask.
Would be cool! I do some long form video, but not engineering topics at this stage.
It can be really rewarding but it’s very hard to make it pay for the hours of production involved.
I totally get it. Maybe a future perk for the members area.
Maybe an animated slide show. It would also provide an easy way to insert ads. /s
This article should be mandatory reading for the couple of guys on here that insist hybrids are stupid because they “generate electricity using gas” so thus they somehow have no redeeming qualities.
The point of a regular, hybrid car is to take a gas engine and make it more efficient. That’s it. It’s not supposed to drive a long time on electricity, it’s not meant to be plugged in, none of that; all of that adds a lot of weight and cost. It takes the weaknesses of a gasoline engine and tries to make up for those as best as it can with a small battery and small electric motor. Those who say a hybrid is pointless or stupid because “it has pathetic EV range” or because “that electricity was generated by burning gas” seriously have no idea what the actual point of a hybrid is.
And can someone please do an article explaining a Prius battery? It weighs less than 100 lbs and is smaller in volume than 3 average-sized 12 volt lead-acid batteries. The people who whine about hybrids destroying the environment because of their earth-destroying, unrecycleable batteries and accompanying grotesque weight gain seriously need to do some research. We’ve been recycling lead-acid batteries for decades; nobody is going to just bury a Prius battery in a landfill.
Counterpoint: this should be required reading for the couple of guys on here(actually it’s a lot more than a couple) who grossly overestimate the efficiency of hybrids and seem to think that they will improve highway fuel economy. I started a giant argument here a while back with like 5 people telling me that somehow regen braking is going to gain you fuel economy when you’re driving a steady 70mph on level ground.
No, the point of a hybrid is not to be plugged in and use energy from the wall instead of energy from gasoline; that being said, if I’m gonna lug around(and pay for) electric batteries and an electric motor in my car I better be able to drive using the power of electricity and NOT gasoline.
I also don’t like hybrids that much because the efficiency gains of a hybrid can be accomplished with a lighter or more aerodynamic car, without the considerable cost/complexity/reliability drawbacks of including an entire second drivetrain in the car.
Did you look at the graphic comparing the fuel economy estimates for the hybrid and non-hybrid versions of the Corolla. The hybrid gets a 15% improvement in the hwy number.
There is not an “entire second drivetrain” in a hybrid. In a Toyota or Ford power-split style hybrid the two motors and a simple planetary gear set is the transmission, far more simple, durable and less expensive to manufacture than the umpteen speed torque converter style automatics commonly in use today.
It says 46mpg for the Prius and 40mpg for the Corolla. That’s a 15% improvement. But that is NOT a 15% improvement all else being equal. Did you read the part where Lewin explains that
“It’s also worth noting that hybrids have traditionally been designed for peak efficiency across the board, in a way which regular models are not. Hybrid models often get sleeker, more aerodynamic designs, lower-rolling resistance tires, and other features to further improve their efficiency figures.”
He’s right, you know. That 15% better Prius has a 0.27 drag coefficient while the Corolla has a 0.31 drag coefficient. What’s the difference? It’s a conveniently perfect 14.8%.
You are exactly who I was talking about when I said this should be mandatory reading. The 15% highway fuel economy improvement of the Prius comes 0% from the hybrid system and 100% from the improved aero. A Corolla non-hybrid drivetrain in a Prius 0.27 body would deliver exactly the same 46mpg.
Read that graphic again, the 46 mpg hwy is for a 2024 Corolla with the same body. The base model 2024 Prius FWD has a 56 mpg hwy rating. Certainly the better aero is a major reason for that 20%+ increase over the Corolla Hybrid.
The 15% increase in the hwy economy of the Corolla Hybrid vs the standard Corolla is largely due to the better effeciency of the Atkinson like operation of its engine and that the nature of the powersplit system allows for maximizing the time the engine spends operating at or near its peak efficiency zone.
Found him!
The car on the right is the COROLLA hybrid. Scoutdude pointed out that a hybrid Corolla gets better highway mpg than the gas one does and you completely missed the point and said that he was comparing a Corolla to a Prius.
Let me break it down for you so that even you can understand.
My 2022 Camry Hybrid is rated at 47 mpg highway. The gas-only version of the exact same car is rated at 39 mpg highway. This is with the exact same wheels/tires, exact same aerodynamics, exact same everything else except the addition of the hybrid drivetrain. Yes, I have checked this out for myself, because I actually do research before I post stuff online.
And you know what? Despite carrying all those horribly wasteful batteries and electric motors in there that you hate so much, the hybrid version of the 2022 Camry gets 8 mpg more on the highway! How did that happen??
I know that’s a very inconvenient truth for you, considering that it is apparently impossible for a hybrid car to get better highway mpg than a non hybrid all else being equal.
I would bet you $100 you haven’t owned a single hybrid vehicle in your entire life.
Yep, I misread that graphic to a pretty catastrophic degree.
No, I have not owned a hybrid vehicle, or in fact any vehicle under 25 years old.
No I don’t hate “those horribly wasteful batteries and electric motors”, and I never said anything to indicate that I did. That’s putting words in my mouth and assuming that I have a stance that I don’t have.
I have one question for you: Does your 2022 Camry Hybrid run the engine 100% of the time when you’re cruising down the highway?
Because, while it is thermodynamically impossible for regen or transmission efficiency advantages from the hybrid system to do anything in steady highway cruising, there are still two ways a hybrid could beat a pure ICE car: One, if it has a more favorable final drive ratio. The Camry Hybrid has the eCVT, and a non-hybrid has a regular CVT, so, assuming both are well tuned, that shouldn’t be a difference here at all.
The other way a hybrid could be more efficient on the highway is by doing an automatic pulse and glide; most ICE engines are more efficient at higher load than the 10-15% load that is required for highway cruising, so some efficiency benefit can be gained by running the engine at more than 15% load, less than 100% of the time.
It’s also possible that the Camry Hybrid literally does not get better highway mpg than the non hybrid and the EPA just tests it differently, because they do that. Or that Toyota runs their “Atkinson cycle” more in the hybrid version.
Those are the only thermodynamically possible ways I am aware of that a hybrid Camry could deliver better fuel economy than a non hybrid in ******steady state, constant speed, level ground highway cruising, all else being equal, including engine tuning.******* Are there any other ways I am unaware of, that aren’t “hybrids magically get more energy out of gasoline because the EPA says so”?
I guess you expect me to do all the research for you? Fine.
A last-generation Camry with the conventional drivetrain does not use a CVT, it uses a 8-speed automatic. A quick google search would have told you that, but I guess you couldn’t be bothered.
The eCVT that the Prius/Corolla/Camry hybrid all share is a different kind of CVT. It uses two high-voltage motors working together spinning at different speeds to vary the output speed of the engine to the wheels. Two important things about this:
1) Because the gas-only Camry uses an 8 speed automatic, this very much is a source of the increased highway efficiency that the hybrid Camry/Corolla possess over their conventionally-powered counterparts.
2) Before you use point #1 as an excuse to say that the only reason a hybrid Camry/Corolla gets better mpg than a conventional one is because it uses a CVT instead of an 8 speed auto, the eCVT can only be done in a hybrid car. The traction motors that vary the output of the engine run at more than 200 volts and pull their current from the hybrid battery to do so. So basically, yes, the hybrid part of a hybrid Camry/Corolla is what helps with highway fuel economy.
I actually did do a quick Google search to verify that a 2025 Camry has a CVT, and I don’t really appreciate the insinuation that I am lazy. I made the mistake of trusting the automatic Google results rather than clicking on some links and doing some more reading, but I can’t say that that’s usually necessary. If you want, you can Google “Toyota Camry transmission” and it’ll give you a big old “2025 Toyota Camry CVT”. I’m not usually the type to read incompletely and come to incorrect results, but I’m on a roll today it seems. If you accused me of skimming through stuff and not reading as closely as I should then it would be well deserved.
Yes a CVT over an 8spd auto can certainly explain an improvement in highway fuel economy, although an 8mpg improvement seems high; the 8spd already has like 3 overdrive gears and should be pretty decent in that regard. I cannot imagine that there is a single load scenario where the 8spd’s closest ratio is so far off that a 20% improvement could be gained from gearing alone.
Yes, an eCVT can only be done in a hybrid car, but CVTs are by no means exclusive to hybrid cars. An eCVT works very differently from a belt/chain CVT, but it achieves exactly the same effect of continuously variable gear ratios. In fact, an eCVT is probably marginally less efficient than a chain CVT because a part of the engine’s power has to be converted to electricity and then back into rotational motion in the motors, and this conversion wastes on the order of 10% of that fraction of the engine’s energy.
Worth noting that the traction motors do not pull their current from the hybrid battery per se; if the battery SoC is not going up or down then all of the electrical energy is coming from the generator, and the battery is just hanging out wired in parallel and not contributing any energy to the circuit. Just like how, even though it is connected to the battery, my car radio is not powered by the 12v battery, it’s powered by the alternator. In this particular scenario(steady state cruising with absolutely zero changes in load), the eCVT could function without a hybrid battery at all, just like how my radio can still work off of the alternator even if I take my 12v battery out.
I assume from your silence that your Camry does in fact run the engine constantly during highway cruising, as I expected it to.
There’s no need to make separate comments that serve no function except to be rude.
Aaaaaand you did it again.
I compared my 2022 Camry hybrid to a 2022 conventionally-powered Camry. Twenty-twenty-two, NOT twenty-twenty-five! Do you know why I did this?
Because the 2025 Camry is hybrid only! All 2025 Camrys have eCVTs. You cannot compare a 2025 Camry hybrid to a 2025 non-hybrid Camry because they do not make non-hybrid Camrys anymore! Are you awake? You did the wrong google search, completely missed the fact that all the brand new Camry’s are hybrids, and then got offended that I called you out on it.
I’ll keep correcting your mistakes as long as it takes; I am awaiting your follow-up response with bated breath.
There you go: I got offended that you called me lazy, when actually I am putting in the effort, and being bad at it. I, as you already read, freely admit that I seem to be extra good today at reading poorly and making these dumb little mistakes. I’m tired today.
Yes, I admit that I was wrong for looking at a Prius, and I was wrong for forgetting that the Camry just recently changed generations so a 2025 is not the same as your 2022. Because, despite what you already claimed about my character, I am man enough to admit when I am wrong, and I won’t try to hide that I was.
Are you willing to not immediately dismiss my legitimate, honest, and earnest questions now? I want to really learn something useful from this discussion, even if that means I was wrong. I sincerely hope that you also want to learn something from this discussion and not just make fun of me.
Ok, you and I are finally getting somewhere now.
I appreciate that you are man enough to admit your mistakes. I mean that sincerely, I really appreciate it.
I am an honest guy, so I’m going to give it to you as straight as I can.
At the end of the day, yes, I want to learn from this discussion. I have already learned something from Scoutdude. I didn’t really understand the whole pulse and glide thing, but what he said made sense. Good, I want to learn too, that’s really the only reason I’m here at all.
If you want that as well, I will genuinely attempt to help as much as I can. But remember, I’m just a guy with a Camry Hybrid and an internet connection; some of this stuff I don’t fully understand either, however I do know how to look up facts and data. So long as we can go based off of objective data rather than guesses we can all learn something here.
Hug it out, bitches!!
Another wonderful moment in The Autopian History!
For 2025 the Camry is only available in a Hybrid version, thus all 2025s have an eCVT while the non-hybrid 2024s use the 8sp.
Yes the Toyota and Ford hybrids do automatic pulse and glide when operating at a steady state on flat ground. You can see it in the power flow display and/or battery charge indicator. At least on the 2013+ Fords the engine can shut off at up to 80mph. While it won’t shut the engine off on flat ground go down a grade and the engine will shut off and will operate in EV mode for a while until the battery SOC reaches the pulse and glide range.
Yes if the HV battery could be disconnected the eCVT could in theory function. However pulse and glide is more effecient and that HV battery is needed for the starter/gen to start the ICE in the first place.
Ford on their first hybrid trans-axle actually set up the case to put a clutch on the starter/gen so that the vehicle could operate in a direct drive mode but before it went into production they found that the range where that was a benefit was very small.
Now the single motor hybrid systems with a conventional transmission can only be powered by electricity from the battery as they can not operate as a motor and a generator at the same time.
Thank you for the legitimately informative comment! Pulse and glide has to be the main mechanism by which these hybrids would attain any better highway mpg, plus a little benefit from the CVT. And yes, the battery would be very necessary for pulse and glide operation.
Strictly speaking, pulse and glide means that not all else is equal; you can pulse and glide in a pure ICE car too, and it often does improve highway mpg a little. Although I would expect that the hybrid pulse and glide is providing a bigger benefit than an ICE pulse and glide, since 1. The battery means that your pulse/glide cycles can be much longer, and 2. There is no speed fluctuation, so you never have to go faster than your target average speed.
And you pulse at the perfect speed for the engine to produce best fuel economy, excess power not needed for propulsion is directed to the batteries.
A few more numbers from fueleconomy.gov
2024 Camry 4cyl 39 mpg hwy
2024 Camry Hybrid 4cyl 53 mpg
36% improvement
2024 Highlander 4cyl 29 mpg hwy
2024 Highlander Hybrid 35 mpg hwy
20 % improvement
2024 Elantra 40 mpg hwy
2024 Elantra Hybrid 52 mpg hwy
2024 Elantra Hybrid Blue 58 mpg hwy
30% or 45% improvement
Shhhhh, Rust Buckets doesn’t like it when his conjecture and assumptions are contradicted by actual data!
I am very aware that I read your comment and the article very incorrectly, and that I made a stupid and misinformed argument as a result. I actually already freely admitted this.
Do you also admit that:
I’ll start taking the questions you have directed at me seriously when I don’t have to spend all my time correcting all of your mistakes. Yes, I think me accusing you of skimming was in fact “well-deserved.”
Not trying to pile on here as I read the full thread and you were more than humble, this just seemed the best point to interject an important point. The reply is only partly directed at you (and that part is in agreement).
You’re right in that chasing hwy mpg is based mainly on aero efficiency, and near a point of diminishing returns.
The big thing that is being overlooked is the 70% increase in city (aka. commuting) mpg. This has huge effects in a lot of peoples’ daily fuel consumption and resulting air quality.
I’ve been advocating for a while that to really get where we need to be from a vehicles emissions standpoint (or even cutting fuel consumption to further energy independence if that’s your goal, they don’t have to be mutually exclusive) is to continue focusing on the low hanging fruit while leaving the single-digit gains for later.
Yup even if hybrids didn’t get better hwy mpg the increase in “city” mpg is significant and would be worth it by itself.
Anyone else feel like the industry in general is way farther behind on hybrids than they should be?
24 years ago Honda had the Insight getting 70mpg, 15 years ago the Volt was getting 30 miles of electric only range.
Today the Honda Civic hybrid gets 50mpg, and Chevy doesn’t even offer a hybrid, along with Nissan, Subaru.
I know the rest of the world was bullish on EVs but a little diversity couldn’t have hurt.
That seems like an apples to oranges comparison if you ask me.
So no, I don’t think modern hybrids have fallen behind, they simply are being tasked to do a whole lot more than we ever asked of the Honda Insight.
Now, whether or not plug-in hybrids have increased their electric-only range enough over the last 13 years is another question entirely…
Great point on the epa numbers getting updated, I keep forgetting about that. But to my other question on car makes that had hybrids but dropped them. Like Chevrolet went all in on EVs so kind of get that, but what about Subaru? They can make an EV with Toyota but not get any of that hybrid goodness?
I honestly have no idea what Subaru is doing. They have a loyal base and attract lots of outdoorsy types, but they have squandered much of their goodwill with their CVTs, anemic yet thirsty engines, and pain in the butt reliability issues that they just can’t seem to stop making. But there are probably at least two reasons why they aren’t using Toyota’s hybrid system.
I feel like Subaru is kind of like the Stellantis equivalent in Japan right now; they are simultaneously underinvesting in their vehicles and coasting off of their old reputation, but it’s eventually going to bite them in the you-know-what. They have a few advantages over Stellantis: they haven’t killed off all their most desirable models, they aren’t priced like premium products, and they have plenty of crossovers to sell, but besides that, they’re in the same boat.
Subaru needs engine designs from this century like, yesterday, and they need to seriously improve their reliability/quality.
Subaru has announced that the Forester will have an available hybrid model in the US market next year. The hybrid system should be similar to the Toyota system, as was the 2019-23 Crosstrek Hybrid’s system. I should point out that the AWD on the Crosstrek Hybrid was NOT the electric rear drive axle type that Toyota uses on certain models. The AWD on the Crosstrek Hybrid was contained within the transmission unit and it used a conventional rear diff, similar to the one used on conventional Crosstreks. Both the front and rear axles were driven by a combination of power from MG2 and (if running) the ICE.
People are regularly able to beat those EPA numbers though. My record is 80mpg.
I understand. My point however is not that the EPA numbers are gospel, but that they facilitate a comparison between two different vehicle’s efficiency because they get tested under the exact same conditions.
Heck, even the EPA has been quoted as saying as much.
No, I don’t feel like the industry is behind on hybrids because a 24 year old Insight gets better mpg than a 0 year old Civic Hybrid.
Of course an 1800lb manual transmission 3cyl two seater streamliner with 73hp gets better fuel economy than a 3000lb CVT 4cyl five seater with 200hp.
The hybrid system in the new Civic Hybrid is probably considerably more effective than the hybrid system in the old Insight, but you ain’t beating physics. The industry isn’t behind on hybrids systems, the industry is behind on actually designing cars for efficiency.
There’s no fighting thermodynamics; making a car bigger and heavier will ALWAYS make it less efficient all being equal. And, despite what the EPA might tell you with CAFE, fuel economy improvement over time is NOT inevitable, nor is it necessarily even possible without making cars smaller.
I just think they are doing hybrids all wrong.
I don’t want a 200hp internal combustion engine and a 80hp electric motor.
I want an engine that produces the absolute bare minimum, to push the vehicle along at 75mph, efficiently. This means I can use the engine for long distance road trips, and get relatively good MPG. I don’t need crazy power from the engine…
because I want like a 500hp electrical motor, with maybe a few minutes of wide open throttle capacity. Maybe even like 90 seconds. Maybe less?
For a decently fast street car, the amount of time you actually spend at 100% throttle is VERY small.
I basically just want a fast AF electric car, with a super tiny turbo diesel or something that weighs nothing, lasts forever, and just charges the ‘fun battery’ over time.
While a diesel is definitely more efficient than a gasoline engine, and much more efficient if run as a generator, it is heavier and more expensive to make, especially with all the new pollution controls (SCR & DPF) which also reduce its reliability to on-par or below of a gasoline engine. It comes down to numbers, nobody would pay twice the price of a Prius for a similar diesel hybrid, even if it would be twice as efficient (it wouldn’t be twice as efficient, more like 30-40% more efficient).
All your points are valid… except a diesel version is not going to be twice the price. It’s definitely going to be more expensive, but not double.
Twice the price of a Prius?
A Ram 2500 with no options except a diesel engine costs 19% more than a Ram 2500 with no options at all. Identical numbers for a Ford diesel. These are for a base model pickup, on the pimped out crew cabs that most people buy, that $10k option is only 10-15% of the total price.
These are 2024 DPF, DEF, high pressure common rail diesels which have considerably more horsepower and features than their gas counterparts.
What on earth makes you think that making a Prius diesel would increase the price by 100%, or even 20%?
And a 30-40% improvement in efficiency for a 10-20% increase in price sounds like a STEAL to me.
I’m not sure a diesel is more efficient anymore:
“According to a statistical analysis of the maximum thermal efficiency of mass-produced 1.5- to 2.0-L engines since 2018, the maximum thermal efficiency of traditional engines lies mainly between 37% and 40%, while that of hybrid electric vehicle (HEV)-specific engines has reached 41% to 43%. The thermal efficiency of the HEV-specific engine is higher than that of the traditional engine, mainly because an HEV can compensate for the power demands of the entire vehicle by adjusting the drive motor torque to ensure that the engine always works in the most economical fuel consumption load area.”
https://journals.sagepub.com/doi/10.1177/16878132221125032
That reminds me I wonder if anyone is doing any experimenting with use of thermo-electric generation recouping electricity, either piezoelectric, piezoresistive or sterling engile, from hot ev coolant?
You have figured out a range extended electric car. These exist, like the i3 Rex.
Except that isn’t fun.
The problem with the idea of a bare minimum ~50 hp engine is, okay, now what happens if you need to pass or climb a steep grade for an extended period at highway speeds but the battery is at a point in its cycle where the charge is low?
Keeping the battery ready for terrain and passing is the new manual transmission.
You deal with that the same way we dealt with it back in my day with cars of two digit hp. Downshift and it necessary move to the right lane.
Wait a short time. It should develop enough juice to pass someone if that generator is running for a bit.
Do you remember David’s i3?
There was an article where he specifically mentioned that if he drained his battery all the way, the small range-extending engine only provided enough charging juice to allow him to maintain 70 mph. On flat ground. (I think it was 70, I could be wrong; it certainly wasn’t MORE than 70).
That does not bode well for the idea that you could pass someone going up a steep grade when your car probably is already struggling to maintain something around 60 mph. Just saying.
Yeah, but the EV portion of the i3 is weak sauce. Imagine it being developed as a performance car. With a tiny little range extending engine like the i3.
You misunderstand. The problem with David’s i3 accelerating on a dead battery isn’t the electric portion, it’s the range extending engine.
If the range extending engine isn’t powerful enough, it can’t produce enough electricity to power the dead battery and electric motors no matter how powerful they are. That is why David’s i3 struggled, not because its electric motors were too weak.
Nice.
The short answer is that gasoline engines are pretty inefficient, though the gasoline is quite energy-dense. So inefficient that adding batteries and a motor to a gasoline engine results in a net efficiency gain (though less fun to drive).
Next up: Can you explain how much battery (a range in kWh) is in each type of vehicle type of vehicle: Hybrid, Plug-in hybrid, and BEV? And how much they weigh, and which ones are most efficient? How much battery per ton is needed (including the battery tonnage)?
I ask, because we have a ct200h, and I’m guessing the battery is pretty small. Can’t even drive it on Battery alone unless under 10mph (like in a parking lot), and even then, it does this automatically unless there is not enough power.
Also, when driving downhill at a constant cruise-control speed, the battery fills up pretty quickly. Would probably get better MPG with a larger battery (duh), but too late for that unless the future gives us solid state battery packs to replace the current (hah!) batteries.
I’ve heard the NiMH batteries in gen 3 Priuses (including your CT200h) are only about 80 pounds.
It’s funny when I visit the hilly area where I grew up and the greatest strengths of a hybrid work against it–accelerating uphill uses much of the battery and then maintaining speed relies primarily on the gas engine, while going down long hills (in B mode) recharges the battery…right until the battery is full (which you may notice the car tries not to do in normal driving), at which point the engine RPMs jump way higher to do fully mechanical engine braking.
Ford’s 1.1kwh battery used in the Escape and Maverick is about 60 lbs.
I have a gen 3 prius plug-in (2012)
When new the all electric range (up to 65 mph) was 13 miles.
Now the total all.electric range is about 10 miles (240k miles on it total).
When I go down a long steep hill, the “regular” part of the hv battery fills up and if I’m still going down, the “ev only” part of the hv battery begins to fill up and then when I accelerate next it will ne in ev only mode automatically (as long as I’m going 64.mph or below).
If I’m driving faster than 64 mph, the hv battery electricity will be used seamlessly in combination with the gas engine
As an example the standard Prius has a 1.3kwh battery while the Prius Prime has a 13.6kwh battery so about 10x the total capacity. However the full 13.6kw isn’t useable as EV mode as they reserve a certain amount to be used when in standard hybrid mode.
So yeah in the PHEVs we’ve had there have been times when the EV portion of the battery has been depleted, after a long downhill the display will show a few percentage of battery capacity and a few miles of EV range.
Thanks! So, when considering the 80lbs my Lexus battery weighs, the Prius PHEV battery weighs 800lb, and the motor is probably bigger and stronger. Round up to 1000 ish.
Now the question is: how big a battery does a hybrid need? I’m thinking at least twice my size, for my vehicle. Then the question becomes, where does it go? Small car, bigger battery,… Maybe a smaller gas tank? I mean, if I got 50mpg regularly with a bigger battery (get about 40mpg now) I could get by on a 6-gallon tank. But this is where gas’s energy density chimes in.
Um, battery weight does not scale with kwh the way you are assuming.
Straight from Toyota USA’s website:
Base model Prius weight: 3097 lbs
Base model Prius Prime (PHEV) weight: 3461 lbs
That is a difference of 364 lbs, so if we add the roughly 80 lbs weight of the hybrid Prius battery, the Prius Prime has a battery that weighs about 444 lbs. This of course assumes that the bigger motors of the Prius Prime don’t add any additional weight at all (which is unlikely) so the real number is probably closer to ~ 400 lbs for the Prius Prime battery.
Great read as always Lewin
Thank you James!
Honestly I think the future for BEVs is BEVs with small storage areas, where self contained generator units, extended range battery packs, or anything else can stored in them.
By self contained generator units I mean like actual generators. It has its gas tank, cooling system, and emissions all as one unit in a single removable chassis.
If we standardize on the general dimensions then we can have an obscene amount of generator options.
Gas, Diesel, Natural Gas, Propane, Hydrogen, etc.
When your generator needs servicing you just pull it out with an engine crane as one whole unit, allowing you to use the car in BEV only mode till the engine is serviced or perhaps you’ll get a loaner generator.
We have the technology.
Here’s another reminder I should have bought a range extended i3 new when I had the chance.
If I understand correctly, the automotive equivalent of the Diesel-electric locomotive was the Chevy Volt (and possibly also the i3?) I guess the idea wasn’t really valid, because it seems to have been left to die on the vine.
Nope that was GM sacrificing good ideas to appease the bottom line.
The Chevy volt was originally pitched as a series-hybrid, primarily-electric car with a range-extending engine like the i3. When it finally made its debut, it turned out to be just a series-parallel hybrid like a Prius, but with a bigger battery and a plug.
Basically GM invented the modern Plug-In Hybrid before it was even a class of vehicle. Unfortunately, it was about 10 years to market too early, in hybrid gasoline mode it couldn’t get the fuel economy the Prius did, and as is tradition – GM gave up on it right before PHEV sales started taking off.
I owned a first gen Volt for a couple of years. It was a range-extended EV with a 16 kWh traction battery and an 85 hp, 4-cylinder ICE range extender. If the traction battery was fully charged, it would run strictly under battery power. When the traction battery was mostly depleted, it switched on the ICE range extender, which was used to generate electricity to power the traction motor. I believe it could theoretically use the ICE range extender to drive the wheels directly, but that was not how it routinely operated.
Both the EV and ICE motors could drive the wheels. But the ICE could also be used as a generator – unlike the Prius at the time.
The Volt was capable of operating as a series hybrid and parallel hybrid.
Thus, because it was ahead of its time, GM killed it.
Every Prius ever made is capable of operating the ICE as a generator. Otherwise it couldn’t go in reverse if the battery got too low.
As I understand it in the Prius: the ICE all goes through the planetary gear system with the EV motors regardless, where the ICE combined with the EV motor can theoretically drive the gear system backwards. I suppose, in one sense, because there are two EV motors in there, one could be used for motive power whilst the other is used as a generator – which I suppose technically might fall as a series hybrid? But I’m not aware of a mode within the Prius that can solely charge the battery to allow the EV to operate independently but I’d love to read more about if it you’ve got a tech brief on how that works.
Toyota calls the planetary gear set a power split device because is splits the engine’s output into two paths in varying amounts as needed. One of those paths is purely mechanical to the wheels. The second path is to the starter/gen which converts that energy into electricity that is then either sent to the traction motor, the battery, or both depending on the current operating conditions.
One of the most common situations where all of the available engine power is going to charge the battery is after a cold start. Once the engine is started it will not shut off, even if the vehicle is stopped, until the engine and catalyst get to a minimum temp. This of course is done to minimize emissions. So while you sit there and idle at the stop light the starter/generator charges the traction battery. Once the engine has reached that min operating temp it can shut down, the car can and in the right conditions will go into EV mode. The vehicle will drain the traction battery until it is in the target SOC range and the process will repeat. On the 2013-2020 Ford Hybrids they went so far as to have an EV+ mode that learns the places the vehicle regularly Cold Soaks and tries to get the vehicle to those destinations with the battery SOC at the minimum target point to maximize the availble storage space for the next cold start.
In most driving however it works just like Lewin described. They operate the engine at a higher output than needed in the current situation when it allows the engine to operate at higher efficiency. The excess power is stored in the battery to be used later, either in EV mode or giving a boost to again keep the engine operating in that peak efficiency zone.
The best place to learn how the 2 motor power split style hybrids work is Weber Auto’s Youtube channel.
But…… A Volt is a series hybrid, and is not a parallel hybrid*, so it is totally not a series parallel like a Prius.
*The Volt does not have a transmission, and the engine does not drive the wheels……. except for when it does. Imagine the Volt transmission as a 5spd, with gears 1-4 removed. The engine can only engage the wheels at highway speeds. During all driving under 60mph or so, the Volt does NOT and cannot function as a parallel hybrid, and is only a series hybrid.
Actually, the new Honda hybrid system is like that, with most power coming just from electric motors powered by the gas engine generating electricity. There is a clutch pack for steady cruising where that would be more efficient.
No the current Honda Hybrids are the closest thing to a Diesel-Electric loco, as much of the time the engine is not connected to the wheels but at certain speeds it does do a direct, or in the case of the CR-V and reduced direct drive as it is more efficient. Diesel Electric locos are built primarily because it is easier to distribute that much power electrically, and for the CVT like operation.
We are still awaiting that Hybrid with a tiny rotary engine from Mazda.
I’m commenting BEFORE actually reading your article Lewin, because I’m positive that I’m going to enjoy and appreciate it. Thanks!
As you should be; Lewin DELIVERS.
What a compliment! Thank you Scott, very kind of you to say so.
And now that I’ve read it, my confidence in your output is confirmed! This was clear and concise and even though I understood the concept previously, I was still entertained and engaged. 🙂
Plus, by far my favorite car of those used in illustrations is David’s Galactic Gold i3. 🙂 Don’t think I’ve ever seen one that color in person. Not yet anyway, but maybe at the upcoming Galpin show?