Not quite ready for prime time

[mdlbear]

From what little I've seen, Honda's hybrid cars aren't quite ready for prime time. Toyota's Prius is closer, but still not there. The fundamental problem is that they're basically gas cars with electric assist. They should be electric cars with onboard chargers.

An electric-assist hybrid needs a horrendous, complicated transmission to split the load between the two power sources, neither of which is adequate to keep the car going by itself. One thing I noticed test-driving the Civic is a distinct hesitation, when accelerating from a standstill, while it restarts the gas engine. I'd be worried on a hill. I believe the Prius is smoother, because more of the load is handled by the electric motor, but it's still not as good as it should be.

Get rid of the load-sharing, and things suddenly get much simpler: the only thing connected to the wheels is the electric motor (or maybe you have one on each wheel). The only thing connected to the generator is the gas engine, and it can darned well be a turbine (which is smaller, quieter, and more efficient). And you can run the generator by itself to power your house in an emergency (100HP = 75KW) And the transmission is simpler because electric motors can deliver full torque over a wider range of speeds.

Lighter, more efficient batteries would help, too -- that's another problem with today's hybrids.

Comments

[kshandra]

The weight limit of the Prius is prohibitive, as well. yohannon just looked at them recently...he and I sitting in one would max it out. He and his live-in sweetie would overload it.

[sdorn.livejournal.com]

There are three other problems that were apparent when I test-drove the Prius a few years ago:

• The system was designed for use without a/c. We were driving along in traffic at great Woohoo mpg, when I asked if I could turn on the a/c. Test-drive guy said, "Sure." According to the central dash display, Woohoo mpg plunged immediately to the low 30s (comparable to the 2003 Corolla, which is what we eventually bought).
  
• The Prius is basically an Echo with a $8,000 surcharge we call the hybrid system. I don't know about you, but I can buy a lot of gas for $8,000.
  
• Hybrid-electric or electric cars don't really solve the problem of "energy production" (I know, I know—not my oxymoron, okay?). You still have to transfer enough energy to a storage device to get the car to move. And that transfer process creates pollution, no matter where you do it. The same would be true of hydrogen fuel-cells, too. Bush's support of the "hydrogen economy" idea makes me very suspicious that petroleum and coal would still be major players in terms of providing the immediate source-point energy for splitting all those water molecules. In the meantime, when was the last time that CAFE standards went up? The technology exists to boost fuel-economy standards on all automobiles (including the light-truck category), and that would reduce both pollution and energy use tremendously.

I guess I'm an old-fashioned skeptic, here.

[mdlbear]

I think they put the price differential close to the expected gas saving on purpose.

Hydrogen or electric power is clean if it comes from a non-polluting source like solar or nuclear. But even methane- or methanol- powered fuel cells pollute significantly less than a similarly-powered internal-combustion engine because they're more efficient (hence less CO₂) and operate at a lower temperature (eliminating the NO_x). Even hybrids reduce the total pollution somewhat, because they're running the gas engine at its most efficient speed.

But I still went for gas.

[andyheninger.livejournal.com]

A few Prius comments, having puzzled out what ours is doing, at least most of the time...

turn on the a/c [...] Woohoo mpg plunged immediately to the low 30s

The MPG display is deceiving. It shows infinity (99) when running on electric power, although the energy being used did come from gas. And, when the gas engine is running while driving at relatively low speeds, the indicated MPG is usually low, as a significant amount of energy is going into the battery. So you get these huge swings from 99 to 30-40 that have nothing to do with what the overall milage is going to be.

Prius is basically an Echo with a $8,000 surcharge

For the 2001-2003 model, this was more or less true, although Echos generally weren't as well equipped. (My father-in-law has one of the old Priuses) For 2004, all is changed. The Prius has gone way upscale in size, style, trim quality, and standard features. Option up a Corolla to the feature level of a Prius, and the list price isn't really that much less. And the Prius is an all-around nicer, and somewhat more spacious car.

An electric-assist hybrid needs a horrendous, complicated transmission to split the load between the two power sources

This was one of the biggest surprises to me, once I figured out how the thing actually works. The Prius transmission is, mechanically, one the simplest ever, in any kind of car, in the entire history of cars. No clutches, no bands, no gears engaging or disengaging, no fluid torque converter, only a single gear. A Ford Model T transmission was complicated in comparison.

The transmission is a single planetary gear set. The gas engine is connected to the planetary gear carrier. The wheels are connected to the ring gear. A motor/generator is connected to the sun gear. A second motor/generator is hooked to the wheels (to the output shaft that drives them, anyhow) to let the car run on electric power, and for regenerative braking. That's it. All the transmission power-split voodoo is pure software. None of it is mechanical.

A motor/generator pair that could transfer the entire required driving power would almost certainly be bigger, heavier and more expensive than the Prius scheme of lesser motor/generators plus planetary gear set. I see no advantages to going that way. And you still would need equally clever software to work out when to run the engine (of whatever type) and how engine power (how much is optimum for best efficiency?) should be balanced between battery charging and wheel driving.

Priuses sold in Japan have a button to encourage the car to run in pure electric mode. It lets you make short city-driving trips without starting the engine. I don't know why they don't have it here - I wish they did. Add a plug-in battery charger you'd really have something interesting. A Prius will cruise along quite happily at 40 MPH on electric power only.

There are only a few cases where the Prius behaves a little differently or oddly

• The brakes feel slightly different from conventional all-mechanical brakes, esp. with light braking. Not bad, really, just a little different. The previous generation Prius brakes were worse - the effects of the regenerative braking kicking in were much more noticeable.
• If the engine is running while the car is stopped (can happen when the engine is cold, or if the battery is low), when the engine does shut off, the car will shudder a little. Toyota could eliminate this if they were willing to sacrifice the last drops of energy that they suck from the engine while it is spinning down. But they don't; drawing power from the generator on the sun gear also causes torque on the transmission output, and the car does shudder slightly when it goes away abruptly.
• When creeping slowly up a very steep grade (15%+), you can feel a pulsing, which I think is probably the motor poles going by at low speed. Let off the brake without touching the gas on a similar grade, and the car will roll backwards slowly with a similar pulsing.

That's about it. In my opinion, Toyota has pretty much worked the kinks out of the design. The biggest remaining question is how long do the batteries really last.

[mdlbear]

Good to know.

... and welcome to LiveJournal! Have fun!