2023 Prius Prime EV Range

Generally about ~60 mpg highway and ~50 mpg city.

There is no situation in the physical universe where a mass that is accelerating and decelerating uses less net energy than a mass that travels the same route at a constant speed. Doing so would defy the laws of physics.

 

Mass that travels at constant speed is no different than mass at standstill according to the principle of relativity. In other words, it doesn't use any energy at all. However, the energy isn't lost when a mass is accelerating. This is known as conservation of energy. It is given back when the mass is decelerating. This is the entire principle behind hybrid cars. The only losses happen because of friction, which is caused by aerodynamic drag, tire friction, electrical resistance in the battery circuits, etc.

You need to realize that 50 mpg is way too low for city driving. If it is showing 50 mpg on MFD, it's more like 40 mpg in reality after you account for the battery use and MFD overreporting. You can easily improve it by gentle acceleration and gentle braking and setting the A/C to near the outside ambient temperature. See the following driving tip from Hank Hill:

YARN | I pretend the gas pedal's an egg. | King of the Hill (1997) - S06E04 Comedy | Video clips by quotes | 241c1628 | 紗

 

You're arguing that accelerating a mass to any speed and then bringing it back to a stop requires zero net energy. That's what's commonly called a perpetual motion machine. It's a physical impossibility.

I don't think you realize the extent of my hypermiling. Please see this post. Also this one and this one. Prior to the Prime I drove a 2012 Prius Plug-in for 6 years, which the wife still drives. I was able to get 20+ miles per charge in that car. I say that to explain that I am very familiar with wringing every bit of efficiency out of the car. The lower city driving efficiency is not because of driving habits, it's because stop and go driving is not as efficient as driving at a constant speed.

 

Yes, you can accelerate a mass to any speed and then bring it back to a stop with less than 1% or even much less energy loss. No one is claiming that you can have a system with absolutely no friction at all, but there are many systems where friction is nearly negligible. Moreover, perpetual motion machine refers not to a frictionless system but to an engine that sucks energy from the environment to generate work, which is not possible according to the second law of thermodynamics. Coming back to inertia, there are flywheel energy storage systems that are nearly lossless:

Flywheel energy storage - Wikipedia

In that case, I don't know why your city mileage is so poor. It is even less than the EPA mileage, and many of us do much better. My HV DTE is approaching 700 miles, and my EV DTE is approaching 40 miles.

 

That wikipedia article says:
"Conversely, flywheels with magnetic bearings and high vacuum can ... and 85% round trip efficiency."

That seems quite short of your "nearly lossless" statement, or your 1% loss claim.

"City" mean greatly different things to different people on different routes in different conditions. Virtually nobody has a drive cycle matching the EPA dyno test definition.

The conditions he described are much harsher than the EPA City test cycle definition -- shorter distances between stops, greater idle time, lower average speed, and heavy A/C use -- so he should be getting lower figures.

 

If that were possible you could use the 6 kWh Prime battery to drive yourself about 83 miles. How? Floor it for the 30 seconds it takes the car to go from 0 to 100 mph and then gently apply the brakes to recover 99% of that kinetic energy. Each time you do that you will have traveled about 0.83 miles. You'll be able to do it 100 times, losing 1% each time.

 

Current state of the art for flywheel energy storage is 93.7%, which is excellent for something that rotates at as high as 100,000 rpm. I was trying to explain the inherent lossless nature of inertia, which the other poster didn't realize. I wasn't trying to give exact efficiency numbers. With the Prius Prime, I expect the regenerative braking to be as efficient as around 80% if braking and acceleration is very gentle.

Applied Sciences | Free Full-Text | A Review of Flywheel Energy Storage System Technologies and Their Applications

 

That isn't just a little bit higher than the round trip efficiency estimates we have seen for previous Prii, it is far far higher. Enough so to need some backup evidence.

Glancing at that paper, I'm not sure its round trip is comparable to the full pavement-to-battey-to pavement round trip of the Prime, including all the drive train losses through the tires, wheels, drive shafts, gear sets, M/Gs and motor controls. The flywheel storage round trip path seems more comparable to just the HV-bus-to-battery and back segment of the longer Prius power flow path.

 

You don't understand the difference between conservative and nonconservative forces. You lose the energy through aerodynamic drag, which becomes incredibly huge at 100 mph, tire rolling resistance, various frictional forces in the vehicle, electrical losses (internal resistances of the battery, inverter, etc.), which are all nonconservative. All this energy is lost as heat.

Inertia isn't energy lost by a nonconservative force. You gain it back to a large extent through regenerative braking, as long as the acceleration and braking are both very gentle. You don't gain back the various nonconservative energy forms I listed above, which are lost as heat for good.

 

I have no idea what you mean by round-trip efficiency.

I have studied regenerative braking in the Prius Prime. It is definitely around 80% efficient. How do I know? I watch my drive monitor. I get about 6.9 mile/kWh. During the trip, when I gently stop at a red light, it increases to 7.0 miles/kWh. After I gently accelerate back to cruising speed, it drops back to around 6.8–6.9 miles/kWh, and during cruising it will go back to 6.9 miles/kWh again. So, regenerative braking is extremely efficient as long as both the acceleration and deceleration are very gentle. I said 80% efficient, but it is perhaps almost 90% efficient.

 

The lossy or lossless nature of inertia is irrelevant to the discussion. The only relevant question is whether it takes more energy to accelerate than it does to maintain a constant velocity. Newton's Laws are instructive here.

Again, you are misunderstanding the conversation. There is zero loss because of some fundamental property of inertia. The "loss" comes from the simple fact that it takes more energy to accelerate to speed y than it does to maintain speed y. Why is that? Because not only do you have to overcome the aerodynamic drag and friction losses inherent in a moving vehicle, but you have to overcome inertia to accelerate the vehicle. Then there are losses involved in regenerative braking that aren't realized when there is no braking at all. All of that adds up to stop and go requiring more energy to cover the same distance than just go with no stop. It's not a matter of opinion or debate, it's a fundamental law of physics.

 

Indirectly. More succinctly: the copious/relentless use of road salt.

 

In the places I've been out west they usually use sand or "cinders." I wonder why some places still use salt? It's so destructive to vehicles, pavement, and the environment.

 

There’s been “talk” of supplementing salt with beet juice, sprayer applied, some other supplements, all with the aim of reducing the damn salt. Never happens though.

In our neighbourhood litigation conscious mall owners are the worst: carpet bombing their properties with salt half the year.

 

It doesn't take a lot, especially on asphalt. Once you open some holes the sun does the rest.

 

Apparently, you never lived in the northern climate? Where the daytime high does not reach 0F, sands or cinders on packed snow-turned-to-ice provide no traction aid and a small amount of salt does not help alleviate the problem of black ice which can be even worse than solid packed snow.

 

As a Chicagoan of 50 years, I've had the sad duty of sending several otherwise-good cars to the junk yard because underbody damage due to salt and constantly-wet undercarriages for 5 months of the year. Had two cars lose brakes at very inopportune times due to rusted-through brake lines. Lost power steering on one due to PS lines rusting out - had to replace two power rank & pinions because of this. Also had fuel and transmission cooler lines go that way.

Getting 100,000 before rust took the vehicle was unknown to me.

It wasn't a problem with some older cars. I guess the newer, lighter (thinner) metal of the steel lines just rust through faster.

Contrast that with cars here in NE Texas. I have a 2000 Ranger that has 344,000 miles on it and the bolts under the truck come out like they were installed yesterday.

Once a car is "infected" with road salt, even moving it to a warm, dry climate "for it's health" can't save it. My mother's '96 Grand Prix has rusty chunks falling off of it still - even though it's been in Texas for 6 years.

"Rust never sleeps"

Posted via the PriusChat mobile app.

 

Sun? What sun? Is that a SoCal thing?

Yes, we really do know what sun is, but in these winter conditions, it can be a very infrequent visitor, kept away by days on end of 100% overcast.

In my climate zones, sand and cinders sprinkled atop ice are a major traction aid. Though this benefit does vanish if or when the sand gets buried or encased by an additional ice layer.

Here, black ice is virtually always worse than solid packed snow. Though the degree depends on the glazing on the snow, which gets worse as more traffic turns it into ice.

 

I do not know. Lived in Colorado with temperatures as low as -40. It was cold enough that you'd occasionally have to get out and kick the ice out of your wheel wells so the tires would stop rubbing. Nobody was retarded enough to try and melt the ice at that point (salt doesn't work below -20). You just drive on it.

EDIT - Drives me crazy that the forum software will not permit you to write d-u-n-n-o

 

I'm using the same meaning as defined and used in the wikipedia article you linked at post #44, and as used in the Applied Sciences article you linked in post #47. If you don't understand that meaning as used in your own reference materials ...

Your 80% and 90% efficiency claims don't follow from those observations at all.

For an example of how to get a somewhat meaningful estimate, try climbing Pikes Peak in EV mode, then descend strictly on regeneration. (If it runs out of battery on the way up, just turn around right there.) Compare how many kWh are needed to climb, vs how many are recovered on the descent. While still not ideal, that exercise will give a much more meaningful figure.