Prius seldom runs on batteries alone?

You are right about the way locomotives operate and why they are diesel-electric (as are many truly huge machines). But you are mistaken to call them hybrids - they have only one power source, the diesel engine. They just have electric transmissions.

Hybrids today get their main efficiency improvement from not using the engine as much to do ludicrously inefficient work. As the OP noted, the engine is still used at times that don't make a lot of sense. Blame that on the infancy of the technology.

Actually, it is an engineering solution to a fundamental conceptual problem. Even as a teenager learning about cars I was struck by the horrible inefficiencies of using large engines to put out negligible power for nearly the entire range of the car's operation. But it was the '60s and gas was cheap. When I first heard about hybrid power trains (around 20 years ago) I immediately recognized them as the solution to the century-old problem.

Ah - that's where you are 100% wrong. One of the central characteristics of hybridization is that the acceleration performance is independent of the power plant capacity, just as a conventional power train's performance is independent of fuel tank size. The engine can be off or just plain dead without affecting the immediate performance of a serial hybrid (none in production yet, sadly). A serial hybrid is essentially an electric car with a charging system on-board. Right now the technology exists to build a serial hybrid that will give the hottest conventional power trains a run for their money; a Tesla

with a small generator tucked somewhere would qualify. Honda and Toyota have both demonstrated concept cars that clearly fall in the high performance range and deliver fuel economy in the miser range - 400 hp and an estimated 40 mpg for the parallel hybrid Honda and 400 hp and 32 mpg for the series-parallel hybrid Toyota. Honda engineers pointed out in the Popular Mechanics article back then that using electrics for torque provides off-the-line acceleration equivalent to a 600 hp conventional power train. Toyota simply mentions 0-60 mph in 4 seconds. Mike

I think you misunderstand the statement. If the meaning was "the car reuses only part of the energy that was regenerated" that matches my experience and even the logic - there is considerable loss and waste in the process. Toyota says "up to 30%" of regenerated energy is reusable, so the process is pretty lossy. But it isn't nearly as inefficient as getting the energy out of an engine running at 10% power, so it still contributes to the overall gain. There is a widespread misconception that regeneration is a major source of the hybrid's efficiency advantage. In actuality, it is a very minor contributor.

Mike

Okay if you don't want to call a diesel-electric locomotive a hybrid, that's fine with me. But you shouldn't call hybrid cars hybrids either. They get all of their energy from their IC engine also. The only difference is that hybrid cars also have a mechanical drive train along with their electrical one.

No, it uses the IC engine more. The IC engine powers the car at all times, even when it isn't running. If the IC engine isn't running, the car is using energy produced by the IC engine at some time in the past and stored in the batteries.

You're confusing acceleration performance with efficiency.

Mike, you can't ignore physics. It takes energy to accelerate mass. Increase the mass and you have to increase the energy input to maintain the same performance level. That's why all economy cars are small and light. More mass also equals higher rolling resistance which requires energy to overcome.

You can use a battery and electric motor to increase the acceleration performance of a car with a small IC engine but you will have to put back the energy you have used at sometime in the future. Each time you convert from one form of energy to another, you will have losses which can't be overcome. You start out with the chemical energy contained in a gallon of gas. Then you burn that gas to produce heat energy but you can't capture all of the heat. You convert that heat energy into mechanical energy with an IC engine which has internal friction losses. Both hybrids and conventional cars have these same losses. To this, a hybrid car adds changing that mechanical energy into electrical energy using an alternator, friction losses and heat losses. You use that electrical energy to recharge a battery converting electrical energy back into chemical energy with it's associated losses. Then, at some time in the future, you discharge that battery converting its chemical energy back into electrical energy with more losses and that electrical energy back into mechanical energy with even more losses.

There ain't no such thing as a free lunch. Perpitual motion is a thing of fiction. If you believe all of these conversion losses add up to an increase in efficiency then you might want to buy this ethanol plant I have for sale.

Don't get me wrong, I like ethanol. When its aged in charred oak barrels for 10 years or so and then mixed with a little water. But burn it for fuel....man, that's just plain wrong.

I guess every manufacturer does it differently. Honda cruise control will remember the speed until you shut off the engine or at least the CC master switch. However, the CC cannot be engaged at speeds below ~20 mph. I think they want to prevent someone from inadvertently engaging the CC and having the car jump from a stationary position.

The Prius can run for a very short time on battery only, but the battery pack isn't large enough to run the car very long or very fast on battery power alone.

How is improving fuel efficiency a political problem?

Your theoretical argument about efficiencies reminds me of creationists who want to make statistical arguments to claim evolution couldn't happen. Dude, the proof is right before your face. Hybrids get much better mileage than a similar/identical car with similar performance with only an ICE.

But you are neglecting the factors which make hybrids more efficient:

The electrical system provides a means of recovering kinetic energy during braking. The energy which would have gone into heating the brake rotors (and wearing out the pads) is converted to energy stored in the battery. Virtually all of the battery charge comes from this source. Even 50% efficiency in recovery of energy which would have been wasted is efficient.

The availability of energy stored in the battery means that the engine doesn't have to provide all the energy under conditions of maximum demand. This allows the engine power to be down rated and therefore run at more efficient (higher) power levels more of the time, e.g. cruising.

The availability of electric drive allows the engine to be shut down at times when it is least efficient, e.g. idle and low speed operation.

But don't try to factor all this together, just look at it as a black box. You put gas in and go farther and/or faster than in a comparable non-hybrid car. What more evidence do you want?

If it is in Scotland and they are aging it for at least 12 years, let me know.

You act like hybrids are hydrogen fuel cells. People are driving hybrids now and getting far better mileage than with conventional cars. It is a proven, practical technology. Using your reasoning, a Prius should be getting 16mpg and no one would be selling them, let alone buying them.

But they make it with corn. If they were making it with barley, you would have a point. ;-]

Yes, and you've already said that that was on a pre-production model in 2000. The car has had numerous changes since then! I suggest that you try another week test drive in a current NHW20 Prius.

(There's also far better emissions controls (notorious for lowering fuel economy) since your AT Tercel... and I won't get into the apples and oranges of comparing a manual to an automatic CVT...)

2004-2007 UK tire Bridgestone Turanza ER30 195/55R16 87V

(Note the different size than the US!)

UK and Canada uses MPG using imperial gallons. Canada and most everywhere else use l/100km. Japan still uses km/l.

Most anti-hybrid kooks are narrowband thinkers. They don't like to see the world as a web of influences. A simple straight line is about as complex as they can handle. For example, your point about the regeneration system sparing the vehicle's brakes ought to suggest to them another indirect saving: less wear on brakes; longer intervals between replacements; less use of materials and energy in their manufacture/replacement; and lower bills. Yet I live in hope that it'll click for them, one day.

That's been my reading of the usual use of the EV switch on the UK NHW20 Prius (see:

) -for moving the Prius a short distance when you don't want the engineto come on (say, shifting a parking space or to not awaken thefamily...)

The EV switch has several limitations to its use. You have to press the button within the first 7 seconds after starting the car. It will not stay in EV mode (will override your button) if the hybrid battery is too hot, the charge is less than 4 bars, your speed is over 28mph, and another reason or two I'm not remembering (hilly area?).

(Considering that the longest run I've heard of for a Prius in electric-only was a UK driver who ran out of gas - was doing for 60mph when ran out of gas, on a long downhill, and made it a little over 2 miles before the battery was down to 1-2 bars... (typical is 1 mile tops on an OOG scenario.) With the 4 bars EV-mode limitation, you probably won't get very far before the Prius overrides your EV choice and turns the engine back on.)

I'll also note that Toyota USA has already stated:

"25. Does Toyota support the modification of my Prius to be a plug-inHybrid and run on electric mode only with a switch?Any such alterations, modifications or tampering with the vehiclevoids the warranty and is likely to be counterproductive for airquality and Prius' durability and safety. "There has also been a post or two from Toyota technicians on otherPrius discussion groups that they've been told to cease working on anyPrius they find (and do no warranty work) if they discover any suchmodification...

I'll note that there are many differences between the North American NHW20 Prius and its worldly cousin, besides the EV button... NA has

15" wheels (elsewhere 16"), different suspension, NA has the bladder fuel tank and the CHHS (thermos), among others... (US is the only place I've noticed as having HID headlamps as an option, for example.) Outside the US the Prius also has the IPA (Integrated Parking Assist) as an option, too (was first introduced on the Prius in 2003 in Japan, is now being offered on some US Lexus models...)

You can view the NHW20 Prius battery charge levels at:

You'd know if you regenerated too much energy by your Prius trying to get rid of extra charge. People who have just come down a long downhill (mountain) often report that at a stop their engine will cycle on/off repeatedly. The Prius will try to bleed off the high SOC by having one of the electric motors repeatedly start and spin the gasoline engine...

(Also, if the hybrid battery cannot accept any more charge, it simply will not. You will no longer have regenerative braking, and will be switched to a higher percentage of conventional hydrolic braking.)

If you are just driving around in the green and don't notice anything else different, then you aren't regenerating more than you can use...

Not on mine -- 2005 UK "T4". It has accepted the EV command as late as about 10 minutes into a run. Haven't tested any later.

Again we differ. Sorry. Mine let it reduce to two bars. (See my past report of "EV" tests done locally.)

The rest of what you say I am okay with, or cannot comment.

The engine isn't subjected to the strains of differing torque. The motor handles that load quite nicely. Extra fuel usually needed (remember the accelerator pump?) when lightly stepping up the speed is nicely handled by the motor instead.

If someone wanted to get off the starting line as fast as I can they better re-do their fuel economy calculations and stop lying through the teeth about that one-time 36 mpg fillup. Man! You might think us hybrid owners just fell off the alien turnip truck. mark_

What I am pointing out is that efficiency has increased along with performance - that is a basic characteristic of hybrid cars. Your premise was that it couldn't be done.

If all we were doing was accelerating mass, there wouldn't be an issue. The fallacy is that it takes some specific energy to accomplish the movement of mass from one place to another, even if the height of the two points is the same. That is not true at all; the efficiency of that operation is always zero since the final potential energy is the same as the initial potential energy. The question is how much energy is going to be wasted in the losses.

For the sake of argument we can keep the frictional losses the same, in which case the question is in the efficiency of the motive source. That is where conventional power trains are so dismal, running at a tiny fraction of their full power output and suffering the staggering losses that go with it. Hybrids make their biggest gains by using the power plant more efficiently. Not that much more efficiently at this stage, but doubling the efficiency from dismal to lousy is no big trick. There is something very wrong with using a power train that is less efficient at 30 mph than at 60 mph.

The proof is in the actual performance - even hybrids such as the Prius typically double the fuel economy of equivalent conventional cars in town. On the highway, where the air resistance losses are dominant, the advantage is much lower.

Mike

writes:

Yeah, I was just paraphrasing from what I could remember... I know that I've seen someone quote the actual section from the UK owner's manual, but I couldn't find the post while looking.

I can post the section from the European 2004 New Car Features manual for the Prius. Page TH-20 (Toyota Hybrid System - II), "9. Motor Drive Mode Control."

1) General =E2=80=A2 For purpose of realizing a low level of noise by a garage after midnight and in the small hours as well as reduction of the emission gas in the garage, the vehicle is driven with only MG2 by manually pushing on the EV mode switch located on the instrument panel. =E2=80=A2 When the EV mode switch is pushed on, the EV mode indicator light located in the combination meter will be illuminated. 2) Operation =E2=80=A2 This mode is activated by manually pushing on the EV mode switch. =E2=80=A2 Under normal driving condition with the EV mode switch off, the vehicle starts up with MG2 only, and the engine will be activated by an accelerator pedal position angle or decrease in the SOC to generate motive force. If, however, the EV mode switch is pushed on, specified values that activate the engine will be modified to expand range of driving with MG2 only. =E2=80=A2 When the EV mode is selected, the engine is at rest and the vehic= le continues running with MG2 only unless any one of the following events occurs: =E2=99=A6 The EV mode switch is turned off. =E2=99=A6 The SOC decreases below the specified level. =E2=99=A6 The vehicle speed exceeds the specified value. =E2=99=A6 The accelerator pedal position angle exceeds the specified value. =E2=99=A6 The HV battery temperature deviates from the normal operating ran= ge.

The EV mode will become off after running for 0.6 to 1.2 mile (1 to 2 km) of a level road successively with the standard SOC of the HV battery.

What are the major contributors, then?

I'd have to assume shutting down the engine at stoplights helps a lot for the EPA city mileage number.

Good aerodynamics and tires with low rolling resistance, certainly.

Thinking about it, regeneration might be minor, but not "very" minor. What else could cause the jump from 30 to 50 MPG?

Interesting advice -- I'll have to try this.

The B transmission setting is my favored way of doing this. I believe it saves the brake pads, and it does not bother my passengers.

That would go partway to explaining why a US Prius gets better mileage than a UK Prius. Although I can't find the exact size, Turanza have significantly higher rolling resistance than Goodyear Integrity tires. Also the 195 versus 185 width increases aerodynamic drag.