Hybrids - Toyota vs Honda

Regenerative braking is very far down on the list of values in hybridization. The essential purpose is to use the primary power source more efficiently. Putting a 240 hp engine in a passenger car to cruise around town at 35 mph is extremely inefficient. Using a 50 hp engine to do that is far more efficient, but responsiveness suffers badly. We are in the infancy of hybridization now, but as the power technology advances a 50 hp hybrid can be more efficient than a 50 hp conventional car and provide better responsiveness than a 240 hp conventional car. The difference is made up by stored electric power.

In actuality, a car would have to be pretty small to warrant only a 50 hp engine. The design becomes straightforward, though. The power necessary to climb a 6% grade at the prevailing maximum speed (75 mph in the US) at maximum gross weight is exactly the engine power needed. For a mid-size car that is in the 100 hp range, maybe slightly less.

The side effects of running the engine at higher power levels are valuable, too. Hybridization increasingly separates the engine from the driver control, so there are no issues with suddenly mashing the accelerator. Emissions are much easier to control as the engine comes under computer control.

I can understand why there isn't a lot of enthusiasm for the current generation of hybrids. Not only do they have a limited track record, the level of hybridization is not enough to knock anybody's socks off. (Well, mostly not. See Honda's DualNote

formatting link
for a glimpse of what is possible.)

Mike

Reply to
Michael Pardee
Loading thread data ...

Your battery has the same basic chemistry, but is a very different animal. In portable electronics the most important design characteristics are power density, light weight, barely affordable replacement cost, and short, spectacular life. The last two are economic considerations. In the Prius power density and light weight are not very important at all, the replacement cost is what it is (since it is not designed to be replaced), and the life is designed to match the life of the rest of the car. If you were willing to have a much larger and heavier battery that used only a third of its potential capacity, and a very sophisticated and expensive charger that was always connected to a charging source when the battery was in use, your battery could easily outlast your satellite phone. I doubt you would like it, though.

Mike

Reply to
Michael Pardee

Nope - 100% covered.

Mike

Reply to
Michael Pardee

So you would like us to believe the useful life of a Pruis is 8yr 100K? A Corolla that can be had for 5,000 less will easily last to 200k or more, don't you think All the more reason one would be better off buying a Corolla ;)

mike

Reply to
Mike Hunter

No - the *warranty* is 8 yr/100K miles. Engine warranties (like the one in the Corolla) are typically 3 yr/36K miles, but I'm sure you expect more.

Mike

Reply to
Michael Pardee

We shall see. NiMH batteries typically have a reduced charge cycle lifetime compared to NiCADs. That is one reason NiMH never caught on in power tools where a contractor might cycle a battery several times per day.

Lifetime in cars is going to be highly variable depending upon usage patterns and random manufacturing variations.

John

Reply to
John Horner

One problem with that is the fact that the stored electric power eventually runs down. It would not be fun to be in the passing lane on a long uphill section of road going around a vehicle only to discover that your battery storage has just been exhausted and that the available torque is suddenly reduced 50%. Yikes!

One thing hybrids bring into the equation is a significant depenence on near term prior history to a degree which conventional engines do not.

John

Reply to
John Horner

It's all a matter of design. In your example, a properly designed hybrid will not run out of passing power because the engine power was enough to maintain full legal speed, while passing power is available because it was not needed to reach the cruising speed. A major reason multi-hundred horsepower engines are used in passenger cars today is to provide that margin, in spite of the economy penalty the vast majority of the time.

Even in the previous generation Prius - the one we have - our battery has never dropped to "empty" (actually something like 50% charge) although we live at 7000 feet and have made trips with ful load to Washington state and the LA area. I've never heard anybody complain about that happening, either. It just isn't a problem.

Mike

Reply to
Michael Pardee

The Prius first went on sale in Japan in 1997, 8 years ago. I don't have solid information, but AFAIK no reports have come out about failures of those batteries.

As you say, we shall see.

Mike

Reply to
Michael Pardee

I wasn't talking about the Prius, I was talking about your hypothetical vehicle which you say would have a much smaller conventional engine than does a Prius.

John

Reply to
John Horner

Clearly not every Prius owner is a happy owner. Look here:

formatting link

Reply to
John Horner

formatting link
But out of those 18 polled, only 1 reported a premature battery failure.

Reply to
High Tech Misfit

Right - the basic principle is to size the engine for the largest continuous output power required. Making it smaller will cause exactly what you describe (running out of power on long, hard uphill slopes) while making it larger is just a waste. Making a hybrid with a 50 hp engine (as I used as an earlier example) works just fine in the flatlands but would get a poisonous reputation for more general use. I used 50 hp as an example for the illustration of moving a car around in town in comparison with using a 240 hp engine. I realize in looking back that confused the issue. Sorry about that. It is useful to note that the driver wouldn't necessarily notice the difference in performance between a 50 hp engine and a 100 hp engine except for the hill climbs.

Mike

Reply to
Michael Pardee

formatting link

That is the link I posted somewhere above as a tinyURL. Note the battery failure post is awry; there is no sulfur in the hybrid battery (NaOH electrolyte, not H2SO4). The 12V aux battery, which does have a fairly high failure rate, is an AGM battery. It can produce sulfur dioxide, while the hybrid battery can't.

Still, no car makes everybody happy.

Mike

Reply to
Michael Pardee

Not necessarily. It would depend at what RPMs each engine produced its maximum torque. It is after all tongue, not HP, that get the vehicle going from a stop and what keeps it going, at speed, up a long grade. The Pruis uses the electric motor when staring and adds it on grades because electric motors develop their greatest amount of tongue at start up. That is why most Toyota are under powered, compared to many of its competitors vehicles. . Toyota, like many import brand engines are designed to produce their HP at higher RPMs than the engines in domestic brands, that is why they run out of tongue rather quickly at speed.. The reason is domestics sell mostly automatic tyrannies in the majority of their vehicles that are equipped with tongue converters. On the other hand Japanese brands which use the same engines in cars sold in other countries that have a much larger percentage of their vehicle equipped with manual tyrannies. With a manual tranny the gear selector can be used to stay on the tongue curve to climb grades, particularly long grades. Most drivers of automatics are want to run their cars in the lower gears to stay on the tongue curve. Follow a Corolla equipped with a manual tranny up a long grade and it will quickly drop off the prevailing speed, unless the drive reverts to lower gears. Follow one with an automatic and you will see it runs out of gears trying to maintain speed, and the speed quickly drops off, because few drivers are willing to run their engines at the much higher RPMs in lower gears needed to maintain the prevailing speed.

mike hunt

"Michael Pardee" . Sorry about

Reply to
Mike Hunter

hybrids don't just work by capturing braking energy.

They run a more fuel efficient cycle with a longer expansion stroke. The Miller/Atkinson cycle. They can do this because acceleration is supplemented by the battery. They also have a smaller engine b/c it can use batteries to accelerate.

By using the Miller cycle they get a higher % of energy out of the gas and into the drivetrain.

It's very ingenious.

Hydrogen is probably never going to "be here". You need a fuel source to get hydrogen. Hydrogen is very hard to transport (harder than natural gas which is difficult enough) and there are no cheap "fuel cells". The advantages of a liquid fuel are great.

I think the next step is using a smaller gas engine and a larger/cheaper battery that you can plug in. You could plug it in for an hour a night and that would take you maybe 30-40 miles. On longer trips and under acceleration the gas engine would turn on. That way you'd be replacing gas with electricity, which can come from nuclear/coal/wind whatever.

Reply to
st-bum

In a serial hybrid (which does not yet exist in mass production) there are no gearing issues because the engine only drives a generator, and the electricity powers the car. We don't have the power electronics yet for serial hybrids, but another decade should get us there.

(Getting back to the subject line...) Presently, Honda's hybrids are what are usually called parallel hybrids. The power train is conventional except that the engine is assisted (Honda calls it Integrated Motor Assist, or IMA) by the electrics. Toyota uses an inventive scheme they call "series-parallel," where a part of the engine torque is directed to the wheels and part is used to generate electricity to power the electric motor. That's why the Prius has no transmission per se (and can't have one), just a skewed differential and a pair of motor/generators. They call it an Electronic CVT. On hard uphill climbs the engine runs up to the maximum engine speed (4500 rpm in the pre-2004s, 5000 rpm in the current ones IIRC) and puts out full rated power with a minimum of drama, completely independent of the car's speed. At lesser power requirements the hybrid computer adjusts the load on the generation part to control the load on the engine, so all aspects of the engine operation are under computer control: mixture, ignition and valve timing, throttle and load... even whether the engine is running or not.

Mike

Reply to
Michael Pardee

How do you figure? You need a power source, not a fuel souce. The power is electrical. It can be generated from wind power and solar power. The current hydrogen research being subsidized by the Bush administration is indeed planning on the oil industry being the primary source of this "fuel" you mention. Otherwise they wouldn't be subsidizing it. That's one of the main reasons hydrogen has been put on the back burner for 30 years. Anyone with a windmill, the production equipment, and a storage tank can produce hydrogen. No profit there.

Hydrogen can be pressurized and stored just like propane. It is no more dangerous than gasoline. In fact, in some ways it's safer. After gasoline's initial explosion, the liquid gas remains and burns furiously. Once hydrogen explodes, that's it. It's all gone. Fuel cells are unnecessary. Hydrogen will burn in reciprocating combustion engines just like other flammable gas (natural, propane). All this was known 30 years ago. The boogie-man scare tactics and disinformation are all oil industry bullshit.

nb

Reply to
notbob

Proving exactly what?

Most of the battery-powered devices around my house (headlamps, walkie-talkies, portable radios, alarm clocks, GPS receives) use the same type of battery as in the Prius. They're about a buck each. I get them at Target or some big-box store and recharge them until the kids accidentally throw them out instead of swapping them out.

Reply to
dh

Hydrogen is less dense than propane or natural and takes alot more energy to pressurize it (and higher pressures). Because of the higher pressures, hydrogen tanks on a car would have to have very heavy and thick steel.

As for burning hydrogen in a car, it would be negate the benefits of hydrogen. The point of a fuel cell is the high efficiency. Burning it in an engine would negate that.

You could make a case for combining hydrogen with coal to make diesel fuel. The ease of transport alone would make it worthwhile.

A gallon of gas has about 36 kwh of heat energy. Generating that much heat energy from wind would cost about $2.00 at a minimum. Converting it to hydrogen at 50% efficiency would make it $4 a gallon equivalent. And that's not counting the capital equipment to make the conversion. Then you have the pressurization and transport losses. Oil companies have no fear of "hydrogen". If anything they would encourage the gov't to fund it. It's pie in the sky. What they would fear is coal to oil technologies and conservation.

Reply to
st-bum

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.